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Introduction: Streptococcus pneumoniae is a cause of infections that range in severity from acute otitis media (AOM) to pneumonia and invasive pneumococcal disease (IPD). The 10-valent pneumococcal conjugate vaccine (PHiD-CV10) was introduced into the Icelandic paediatric immunisation programme in 2011. The aim was to estimate the population impact and cost-effectiveness of PHiD-CV10 introduction. Methods: Data on primary care visits from 2005–2015 and hospitalisations from 2005–2017 were obtained from population-based registries. A Bayesian time series analysis with synthetic controls was employed to estimate the number of cases of AOM, pneumonia and IPD that would have occurred between 2013–2017, had PHiD-CV10 not been introduced. Prevented cases were calculated by subtracting the observed number of cases from this estimate. The cost of the programme was calculated accounting for cost-savings due to prevented cases. Results: The introduction of PHiD-CV10 prevented 13,767 (95% credible interval [CI] 2,511–29,410) visits for AOM from 2013–2015, and prevented 1,814 (95%CI -523-4,512) hospitalisations for pneumonia and 53 (95%CI -17-177) admissions for IPD from 2013–2017. Visits for AOM decreased both among young children and among children 4–19 years of age, with rate ratios between 0.72–0.89. Decreases were observed in both pneumonia hospitalisations (rate ratios between 0.67–0.92) and IPD (rate ratios between 0.27–0.94). The total cost of implementing PHiD-CV10 in Iceland was -7,463,176 United States Dollars (USD) (95%CI -16,159,551–582,135) with 2.1 USD (95%CI 0.2–4.7) saved for every 1 USD spent. Conclusions: The introduction of PHiD-CV10 was associated with large decreases in visits and hospitalisations for infections commonly caused by pneumococcus and was cost-saving during the first five years of the immunisation programme. [ABSTRACT FROM AUTHOR]

This study assesses spatiotemporal and sex‐specific growth of Atlantic cod Gadus morhua in Icelandic waters. We use a Bayesian approach which lends itself to fitting and comparing nested models such as these. We then compare fitted parameters of these models to potential explanatory variables using a redundancy analysis (RDA) to look for drivers of growth in G. morhua. Results indicate that models that incorporate differences in growth among time, space and sex are the best‐fitting models according to deviance information criterion (DIC). Results from RDA indicate that capelin Mallotus villosus recruitment and biomass is highly correlated with deviations in the von Bertalannfy growth parameter k and that L∞ is correlated with G. morhua landings in the model that uses year to account for time‐varying growth and estimated G. morhua recruitment in the model that uses cohort to account for time‐varying growth. [ABSTRACT FROM AUTHOR]

Aim: The aim was to estimate the impact of the 10-valent pneumococcal vaccine (PHiD-CV) on tympanostomy tube placements (TTP) in children under five years of age in Iceland.Methods: This population-based observational cohort study followed 11 consecutive birth-cohorts 2005-2015 from birth until their fifth birthday. Population registries were merged using national identification numbers. The risk of TTP was compared between birth-cohorts adjusted for the number of previous otitis media diagnoses and antimicrobial prescriptions. A Cox regression model was applied and the hazard ratio (HR) of TTP was estimated between each birth-cohort and the last vaccine non-eligible birth-cohort. The vaccine impact of PHiD-CV10 on TTP was estimated as 1-HR ×100%.Results: In total, 51 247 children were followed for 210 724 person-years, of which 14 351 underwent 20 373 procedures. The estimated vaccine impact on TTP was -6% (95% CI -16% to 2.7%). Children in the vaccine-eligible cohorts had fewer previous otitis media diagnoses and had been prescribed fewer antimicrobials prior to the procedure than children in the vaccine non-eligible cohorts.Conclusion: Despite high uptake of PHiD-CV10, tympanostomy procedures increased in Iceland during the study period. Vaccine-eligible children had milder disease prior to the procedure. The reason underlying these findings are speculative. [ABSTRACT FROM AUTHOR]

Iceland is seismically the most active region in northern Europe. Large single earthquakes (~ M w 7) and seismic sequences of moderate-to-strong earthquakes (~ M w 6–6.5) have repeatedly occurred during past centuries in the populated South Iceland Seismic Zone (SISZ). The seismic hazard in Iceland has mainly been evaluated using ground motion models (GMMs) developed from strong-motion observations in other countries and only to a very limited extent from Icelandic data, despite a particularly rapid attenuation of ground motions with distance in Iceland. In this study, we evaluate the performance of these GMMs against the Icelandic strong-motion dataset, consisting of peak ground accelerations of moderate-to-strong ( M w 5–6.5) and local (0–80 km) earthquakes in the SISZ. We find that these GMMs exhibit both a strong bias against the dataset and a relatively large variability, which calls their applicability and earlier hazard analyses into question. To address this issue, we recalibrate each of the GMMs to the dataset using Bayesian regression and Markov Chain Monte Carlo simulations. This approach allows useful prior information of the GMM parameters to be combined with the likelihood of the observed data and provides posterior probability density functions of model residuals and regression parameters. The recalibrated GMMs are unbiased with respect to the data and have a low total standard deviation of around 0.17 (base-10 logarithmic units). The model-to-model variability in the median predictions vary primarily with distance, reaching 0.05 the lowest for M w 6.3–6.5 at intermediate distances. While the lack of near-fault and far-field data, particularly at large magnitudes, and the different functional forms of the GMMs calibrated to the same dataset may affect the results, the recalibrated GMMs should represent well the ground motions of a typical sequence of moderate-to-strong SISZ earthquakes. We present the recalibrated GMMs of this study as promising candidates for future use in ground motion prediction in Iceland e.g., in the context of either a logic tree or the backbone approach in probabilistic seismic hazard assessment. [ABSTRACT FROM AUTHOR]

Forecasting of glacier mass balance is important for optimal management of hydrological resources, especially where glacial meltwater constitutes a significant portion of stream flow, as is the case for many rivers in Iceland. In this study, a method was developed and applied to forecast the summer mass balance of Brúarjökull glacier in southeast Iceland. In the present study, many variables measured in the basin were evaluated, including glaciological snow accumulation data, various climate indices and meteorological measurements including temperature, humidity and radiation. The most relevant single predictor variables were selected using correlation analysis. The selected variables were used to define a set of potential multivariate linear regression models that were optimized by selecting an ensemble of plausible models showing good fit to calibration data. A mass-balance estimate was calculated as a uniform average across ensemble predictions. The method was evaluated using fivefold cross-validation and the statistical metrics Nash–Sutcliffe efficiency, the ratio of the root mean square error to the std dev. and percent bias. The results showed that the model produces satisfactory predictions when forced with initial condition data available at the beginning of the summer melt season, between 15 June and 1 July, whereas less reliable predictions are produced for longer lead times. [ABSTRACT FROM AUTHOR]

Evidence is mixed on whether society-wide economic conditions affect cardiovascular health and the reasons for the suggested relationship are largely untested. We explore whether a short-term increase in labor supply affects the probability of acute myocardial infarctions, using a natural experiment in Iceland. In 1987 personal income taxes were temporarily reduced to zero, resulting in an overall increase in labor supply. We merge and analyze individual-level, registry-based data on earnings and AMIs including all Icelandic men and women aged 45-74 during the period 1982-1992. The results support the prominent hypothesis of increased work as a mechanism explaining worsening heart health in upswings, for men aged 45-64 who were self-employed. We furthermore find a larger increase in probability of AMIs during the tax-free year in men aged 45-54 than men aged 55-64. [ABSTRACT FROM AUTHOR]

Aims To evaluate the effectiveness of a 6-month, partnership-based self-management programme for patients with mild and moderate chronic obstructive pulmonary disease. Background Self-management is a widely valued concept used to address contemporary issues of chronic health problems. Findings of self-management programmes for people with chronic obstructive pulmonary disease are inconclusive. Design Pragmatic randomized control trial. Methods Patients, 45-65 years old, with mild and moderate chronic obstructive pulmonary disease were invited with a family member. Experimental group ( n = 48) participated in a 6-month, partnership-based self-management programme consisting of: (a) three to four conversations between nurse and patient-family member; (b) 6 months of smoking cessation; and (c) interdisciplinary team-patient-family member group meeting. Control group ( n = 52) received usual care. Data were collected at months zero, six and 12. The trial lasted from June 2009-March 2013. Results Patients with mild and moderate chronic obstructive pulmonary disease who participated in the partnership-based self-management programme perceived less intrusiveness of the disease and its treatment than patients in the control group. Patients in the experimental group did not have better health-related quality of life, less anxiety or depression, increased physical activity, fewer exacerbations or better smoking status than patients in the control group. Patients in both groups found participation in the research useful and important. Conclusion The partnership-based self-management programme had benefits concerning perception of the intrusiveness of chronic obstructive pulmonary disease and its treatment on lifestyles, activities and interests for young patients with the disease in its early stages. High satisfaction in control group, low family attendance and the relatively short treatment period may explain the less than expected benefits of the programme. [ABSTRACT FROM AUTHOR]

Wind energy harnessing is a new energy production alternative in Iceland. Current installed wind power in Iceland sums to 1.8 MW, which in contrast is 0.1% of the country's total electricity production. This article is dedicated to the exploration of the potential cost of wind energy production at Búrfell in the south of Iceland. A levelized cost of energy (LCOE) approach was applied to the estimation of the potential cost. Weibull simulation is used to simulate wind data for calculations. A confirmation of the power law is done by comparing real data to calculated values. A modified Weibull simulation is verified by comparing results with actual on-site test wind turbines. A wind farm of 99MWis suggested for the site. Key results were the capacity factor (CF) at Búrfell being 38.15% on average and that the LCOE for wind energy was estimated as 0.087-0.088 USD/kWh (assuming 10% weighted average cost of capital (WACC)), which classifies Búrfell among the lowest LCOE sites for wind energy in Europe. [ABSTRACT FROM AUTHOR]

Smoking is related to health deterioration through increased risk of various diseases. Changes in this health behavior could contribute to the documented health improvements during economic downturns. Furthermore, the reasons for changes in behavior are not well understood. We explore smoking behavior in Iceland before and after the sudden and unexpected economic crisis in 2008. Furthermore, to explore the mechanisms through which smoking could be affected we focus on the role of labor-market changes. Both real income and working hours fell significantly and economic theory suggests that such changes can affect health behaviors which in turn affect health. We use individual longitudinal data from 2007 to 2009, incidentally before and after the crisis hit. The data originates from a postal survey, collected by The Public Health Institute in Iceland. Two outcomes are explored: smoking participation and smoking intensity, using pooled ordinary least squares (OLS) and linear probability models. The detected reduction in both outcomes is not explained by the changes in labor-market variables. Other factors in the demand function for tobacco play a more important role. The most notable are real prices which increased in particular for imported goods because of the devaluation of the Icelandic currency as a result of the economic collapse. [ABSTRACT FROM AUTHOR]

Instruments that are able to capture changes related to an intervention are of great value to the scientific as well as to the clinical community. The Iceland-Expressive Family Functioning Questionnaire (ICE-EFFQ) measures expressive emotions, collaboration, problem solving, communication, and behavior in families experiencing a chronic or an acute illness. The conceptual framework of the Calgary Family Assessment Model (Wright & Leahey, 2009) was used to construct the original questionnaire of 45 items and 10 subcategories. A total of 557 family members with a recent illness experience of a close relative answered the ICE-EFFQ in three different studies. Principal component factor analysis reduced the original questionnaire to 22 items with five factors emerging and a total Cronbach’s alpha coefficient of α = 0.912 accounting for 60.3% of the total variability. Confirmatory factor analysis from two studies produced the final version of the questionnaire consisting of 17 items and four factors. [ABSTRACT FROM PUBLISHER]

Valid and reliable instruments are needed to measure how family members perceive support from nurses when a family member is experiencing serious illness. The purpose of this article is to describe the development and psychometric testing of a new instrument, the Iceland-Family Perceived Support Questionnaire (ICE-FPSQ). The concepts in the original version of the ICE-FPSQ (suggesting 24 items and 4 categories) were developed from the Calgary Family Intervention Model. In the first phase of the instrument construction, 179 family members answered the original ICE-FPSQ, and 236 answered the questionnaire in the second phase of testing. Principal Component Analysis (PCA) reduced the original questionnaire to 21 items. Cronbach’s α = .959 explained 68% of the total variance, with three factors emerging: (a) emotional support (α = .925), (b) recognition of families’ strengths (α = .926), and (c) cognitive support (α = .841). Confirmatory Factor Analyses (CFA) resulted in a final version of the questionnaire containing 14 items with total alpha of .961 and two factors: (a) cognitive support (α = .881) and (b) emotional support (α = .952). The instrument measures family’s perceptions of support provided by nurses and will be helpful in examining the usefulness of family nursing interventions. [ABSTRACT FROM PUBLISHER]

Aim: Evaluation of long-term outcome of extremely low-birthweight (ELBW) teenagers born in Iceland in 1991-1995. Method: Participants, 30 of 35 ELBW survivors and 30 full term control teenagers (14-19 years), were assessed for disabilities, health problems and learning difficulties. Results of national standardized tests in mathematics and Icelandic language were compared with results of neurodevelopmental assessment at 5 years of age. Results: A quarter of the ELBW teenagers had disabilities. All were initially diagnosed with neurodevelopmental disorders early in life and neurosensory and/or intellectual disabilities were confirmed later in childhood. Chronic lung disorders, neurological problems and psychiatric disorders were most common health problems. Growth parameters were within normal limits for most of the ELBW teenagers. Learning difficulties affected 57% of the ELBW teenagers, 20% attended special education classes and 37% required special teaching. Results of national standardized tests were significantly lower for ELBW survivors and were significantly related to the results of neurodevelopmental assessment at 5 years of age. Interpretation: A quarter of ELBW teenagers have disabilities albeit most of them mild. Chronic health problems and learning difficulties affect many ELBW survivors. Changes with time emphasize need of long-term follow-up. [ABSTRACT FROM AUTHOR]

Bayesian hierarchical modeling is applied to the analysis of annual minimum and maximum temperatures. In both cases the generalized extreme value distribution is selected as the marginal distribution at each site due to its flexibility and theoretical basis. This distribution has three unknown parameters, a location parameter, a scale parameter and a shape parameter. The location and scale parameters are assumed to vary across sites while the shape parameter is assumed to be the same for all sites. The location and the scale parameters are modeled as two independent Gaussian spatial processes which are governed by the Matérn correlation function. These spatial processes play a central role in spatial predictions at unobserved sites. The location parameter is also modeled with a common time effect which includes a linear trend and a linear site effect with altitude, distance to open sea, latitude and longitude as covariates. This model allows for spatial predictions for any set of unobserved sites, the scale of the grid can be as fine as possible as long as the covariates are observed at each of the unobserved sites. Data on the annual minimum and maximum temperatures in Iceland from 1961 to 2009 at 72 sites are analyzed and used to predict the 2nd percentile of the minimum temperature for the 12-month period from July 2011 to June 2012 and the 98th percentile of maximum temperature for the year 2011 for a large set of unobserved sites across Iceland at which the covariates are available. The spatial predictions reveal that the 2nd percentile of minimum temperature for 2011 to 2012 reaches −35°C in the central part of Iceland and ranges from −12 to −22°C around the coast of Iceland with the lowest coastal temperatures in the Northern part and the Northeastern part. The 98th percentile of maximum temperature in 2011 ranges from 10 to 30°C where the warmest areas are found in the Eastern part, the North-Eastern part and the Southern part of the country. The estimated increase in minimum and maximum temperatures over the years 1961 to 2009 is 0.71 and 0.47°C per decade, respectively, while the average annual temperature increased 0.24°C per decade over the same period. [ABSTRACT FROM AUTHOR]

To cite this article: Finnbogadóttir AF, Árdal B, Eiríksson H, Hrafnkelsson B, Valdimarsson H, Lúðvíksson BRúnar, Haraldsson Á. A long-term follow-up of allergic diseases in Iceland. Pediatr Allergy Immunol 2012 Doi: 10.1111/j.1399-3038.2011.01234.x Abstract Introduction: Allergic disorders are an increasing health problem in many countries, in particular among children. We have evaluated the prevalence and manifestations of allergy in a cohort of young Icelanders for more than two decades. Variations in the epidemiology and clinical expression of allergy in different communities may help to identify etiological factors contributing to these disorders. Methods: A cohort of 179 children has been monitored for allergic manifestations for two decades, at the ages of two, four, eight, and 15 years, and most recently at the age of 21 years involving 120 of the participants. Results: Cumulative prevalences of 40%, 45%, and 29% have been observed, respectively, for rhinoconjunctivitis, eczema, and asthma during the study period. None had developed rhinoconjunctivitis at the age of about 2 years, but the point prevalence gradually increased to 33% at the age of 21 years. Conversely, the prevalence of eczema was 31% at the age of 2 years, but gradually declined to 8% at the age of 21 years. The prevalence of asthma peaked at 28% at the age of 4 years, but declined thereafter and has remained stable at about 13% from the age of eight to 21 years. Discussion: The prevalence of allergic diseases is high in Iceland among children and young individuals. Asthma and atopic eczema are very common in childhood, but decreases with age while the prevalence of rhinoconjunctivitis increases markedly. The very high and increasing prevalence of rhinoconjunctivitis among 15- to 21-year-old individuals is noteworthy. [ABSTRACT FROM AUTHOR]

Background: The risk factors for febrile, respiratory, and gastrointestinal illnesses in preschool children at day care centres have not been adequately identified and may differ between countries. Methods: In this repeated cross-sectional and longitudinal study of children at day care centres, we analyzed various potential risk factors for infectious illnesses using a mixed effect hierarchical Poisson regression model. The results of the analyses and the incidence rates of these illnesses are reported herein. Results: The study lasted 2.5 y (2000-2003) and was divided into five 6-month periods (seasons). Nine hundred and seventeen children participated, and their mean age within each season was 3.6-4.1 y. The only consistent risk factors identified were young age and winter season. No consistent risk factors at the day care centres (facilities or hygiene practices) were identified. The incidences of the febrile, respiratory, and gastrointestinal illnesses varied significantly between seasons (winter/summer) and between age groups. Conclusions: Risk factors of infectious illnesses are difficult to identify and because they may vary between countries, international recommendations on expensive intervention strategies are not justifiable. Rates of respiratory illnesses in Icelandic preschool children appear higher than in other countries, but rates of gastrointestinal illnesses lower. [ABSTRACT FROM AUTHOR]

The quantitative connections between subsurface geologic structure and measured geophysical data allow 3D geologic models to be tested against measurements and geophysical anomalies to be interpreted in terms of geologic structure. Using a Bayesian framework, geophysical inversions are constrained by prior information in the form of a reference geologic model and probability density functions (pdfs) describing petrophysical properties of the different lithologic units. However, it is challenging to select the probabilistic weights and the structure of the prior model in such a way that the inversion process retains relevant geologic insights from the prior while also exploring the full range of plausible subsurface models. In this study, we investigate how the uncertainty of the prior (expressed using probabilistic constraints on commonality and shape) controls the inferred lithologic and mass density structure obtained by probabilistic inversion of gravimetric data measured at the Krafla geothermal system. We combine a reference prior geologic model with statistics for rock properties (grain density and porosity) in a Bayesian inference framework implemented in the GeoModeller software package. Posterior probability distributions for the inferred lithologic structure, mass density distribution, and uncertainty quantification metrics depend on the assumed geologic constraints and measurement error. As the uncertainty of the reference prior geologic model increases, the posterior lithologic structure deviates from the reference prior model in areas where it may be most likely to be inconsistent with the observed gravity data and may need to be revised. In Krafla, the strength of the gravity field reflects variations in the thickness of hyaloclastite and the depth to high-density basement intrusions. Moreover, the posterior results suggest that a WNW–ESE-oriented gravity low that transects the caldera may be associated with a zone of low hyaloclastite density. This study underscores the importance of reliable prior constraints on lithologic structure and rock properties during Bayesian geophysical inversion. [ABSTRACT FROM AUTHOR]

Background: Antimicrobial resistance is a public-health threat and antimicrobial consumption is the main contributor. The ten-valent pneumococcal conjugate vaccine (PHiD-CV10) was introduced into the Icelandic vaccination program in 2011. The aim was to estimate the vaccine impact of PHiD-CV10 on outpatient antimicrobial prescriptions in children.Methods: Eleven Icelandic birth-cohorts (2005-2015) were followed from birth until three years of age or to the end of the study period (December 31, 2016). Birth-cohorts were grouped as vaccine non-eligible (VNEC, 2005-2010) or vaccine eligible (VEC, 2011-2015). Data on primary care visits for respiratory infections and antimicrobial prescriptions were extracted from two national registers. Using national identification numbers, prescriptions were linked to physician visits if filled within three days of the visit. Incidence rates and incidence rate ratios between VNEC and VEC were calculated. An Andersen-Gill model was used to model the individual level data, accounting for repeated events and censoring. Vaccine impact was calculated as (1 - Hazard Ratio) × 100%.Results: Included were 53,510 children who contributed 151,992 person-years of follow-up and filled 231,660 antimicrobial prescriptions. The incidence rate was significantly lower in the VEC compared to the VNEC, 144.5 and 157.2 prescriptions per 100 person-years respectively (IRR 0.92, 95%CI 0.91-0.93). Children in VEC were more likely to have filled zero (IRR 1.16 (95%CI 1.10-1.23) and 1-4 (IRR 1.08 95%CI 1.06-1.11) prescriptions compared to children in VNEC. The vaccine impact of PHiD-CV10 against all-cause antimicrobial prescriptions was 5.8% (95%CI 1.6-9.8%).When only considering acute otitis media-associated prescriptions, the vaccine impact was 21.8% (95%CI 11.5-30.9%).Conclusion: The introduction of PHiD-CV10 lead to reduced antimicrobial use in children, mainly by reducing acute otitis media episodes. This intervention therefore reduces both disease burden and could slow the spread of antimicrobial resistance. [ABSTRACT FROM AUTHOR]

Abstract Earthquake recordings on two small-aperture (covering ∼ 1.2 km2 each) strong-motion arrays in Iceland (ICEARRAY I and II) exhibit considerable variations in the spatial distribution of ground-motion amplitudes. To better understand this spatial variability, we use a Bayesian Hierarchical Model (BHM) that incorporates ground motions models (GMMs) for peak ground accelerations (PGA) developed from ground motion databases recorded by the two arrays, respectively. The posterior distributions of the model parameters are then determined using Markov Chain Monte Carlo simulations in the context of Bayesian statistical methods. The BHM allows the partitioning of a GMM into event, station, and event-station terms, which in turn allows the relative contributions of source, path, and site effects to be quantified. The results indicate that site effects can dominate the spatial distribution of ground-motion parameters (e.g., PGA) observed across both ICEARRAY I and II. Although the site conditions across ICEARRAY I have been classified as uniform (i.e., "rock" with a relatively flat topography), station terms contribute ∼ 13 % to the total variability in the amplitudes of predicted ground motions across the array. In contrast to ICEARRAY I, the variation of the geologic profiles and topography is much greater across ICEARRAY II. As a result, the inter-station variability is shown to contribute up to ∼ 57 % of the total variability in the amplitudes of predicted ground motions across the array, with the contributions being less constrained for ICEARRAY II than ICEARRAY I due to the relative sizes of the recorded ground motion databases. These results facilitate our understanding of the key factors that affect the variation of seismic ground motions across a relatively small area. Such a detailed microzonation is of great importance for earthquake hazard assessment on a local scale and has practical implications for engineering decision making. Highlights • The spatial distribution of PGA on two Icelandic small-aperture arrays is modeled using a Bayesian Hierarchical Model. • The model partitions the ground motion variability into event, station, and event-station terms. • The relative contributions of source, path, and site effects and their associated uncertainties are quantified. • The BHM can be used as a practical tool to estimate partially or fully non-ergodic GMMs and their standard deviations. [ABSTRACT FROM AUTHOR]

A fundamental modeling assumption in engineering seismology is that seismic ground motion is affected by source, propagation path and site effects. Contrary to the first two, comprehensive studies on site effects, the localized amplification effects on seismic ground motion due to the uppermost geological structure, have been limited in Iceland. As a result, site amplification has been modeled in ground motion models in a simplistic and qualitative way. In this study, we address this limitation by using the new Bayesian hybrid GMM proposed by Kowsari et al. (2020) to model the recorded ground motions at regional strong-motion stations in southwest Iceland, specifically the peak ground acceleration and pseudo-acceleration response spectra as a function of oscillator period (i.e., PGA and PSA at T = 0.01 - 3.0 s), earthquake magnitude, distance and hypocentral depth, and at first, we omit a site-term. Then, we incorporate the GMM in a Bayesian Hierarchical Model (BHM) that allows prior distributions of model parameters to be used and we partition the model residuals into various terms associated with the source, propagation path and station terms. Through Bayesian inference of the model parameters the results show that the station term residuals reveal a frequency-dependent site amplification at the recording sites. By inspecting this systematic behaviour, we propose four groups of station terms by their characteristics. We then carefully inspect the station locations in terms of their associated geological unit and observe that the geological units and station term groups are qualitatively correlated. By combining the two, we propose the first frequency-dependent average site amplification functions associated with key geological units in Iceland based on age and formation. Provisionally we refer to them as hard rock, rock, (Holocene) lava rock, and (unspecified) soil site classes, respectively. We then update the GMM by incorporating these amplification functions so that it now enables the prediction of PGA and PSA at these four site classes. As a result, the new model standard deviations are considerably lower, with those associated with the event term being τ = 0.05, station terms φ S 2 S = 0.10, intra-event φ = 0.17 and total σ = 0.18 in common logarithm units for PGA. The new site class-specific GMM now enables the site-specific ground motion for separate geological units which in turn improves site-specific seismic hazard assessment and informed site-specific engineering decision making in Iceland. • A new empirical ground motion model without a site term is embedded in a Bayesian Hierarchical Modeling (BHM) framework. • The model is calibrated to strong-motion data from mainshocks recorded in Southwest Iceland. • The BHM reveals the frequency-dependent station terms which are a proxy for localized site effects. • The station terms are correlated to key Icelandic surficial geological units, hard rock, rock, lava rock and soil. • The average station terms for each geological unit have been incorporated into the original ground motion model. [ABSTRACT FROM AUTHOR]

Strong earthquakes occurring frequently in south Iceland are always characterized by intense aftershock activity. The aftershock sequences cause progressive damages to structures and considerable psychological strain on inhabitants as the threat of upcoming large earthquakes looms. In this study, we apply a Bayesian epidemiological spatiotemporal aftershock sequence (ETAS) clustering model to forecast the aftershock sequence that commenced with the damaging 29 May 2008 M w 6.3 Ölfus earthquake. The forecast is carried out manually but in a framework of a provisional operational earthquake forecasting (OEF) system and based on an informative set of ETAS parameters derived from the strong June 2000 sequence in the region. We show that the short-term forecasts are unreliable at the early stages of the ongoing seismic sequence due to incomplete aftershocks collected to feed the Bayesian updating procedure of the ETAS model parameters, mainly during the first hours after the Ölfus mainshock. In contrast, issuing 24-h long forecasts, starting 6–8 h after the mainshock gives the best forecasting results. We allow the daily forecasts to adapt to the ongoing 2008 sequence using the adaptive prior estimation method, i.e., by assigning an informative prior distribution to ETAS parameters for the subsequent forecasting interval based on the preceding ETAS parameter posterior distributions. The parametric posteriors do not show narrow distributions, thus indicating inconsistent forecasting performance, both in stark contrast to the June 2000 sequence. Regardless, our results provide a quantitative estimate of the reliability of the forecasts which is a prerequisite for evaluating their usefulness to civil protection. • Calibrating a Bayesian ETAS model to forecast an intense seismic sequence in Iceland • Short-term aftershock forecasting of the damaging 29 May 2008 M6.3 earthquake • Comparison of retrospective forecasting of June 2000 and May 2008 seismic sequences • Daily forecasts using informative and adaptive ETAS priors over an ongoing sequence [ABSTRACT FROM AUTHOR]

Earthquake ground motion prediction in Iceland where strong-motion data is scarce poses a challenge as empirical ground motion models (GMM) developed from data in other regions systematically fail to capture the consistently large near-fault peak amplitudes and their rapid attenuation with distance from the earthquake source. Therefore, regional GMMs must be constructed but due to the limited data, and none above M w 6.5, earthquake source scaling is unconstrained at larger magnitudes. Instead, physics-based GMMs should be applied based on realistic earthquake source modeling. For that purpose, a seismological model constructed around the specific barrier model (SBM) has been calibrated in the context of the stochastic method using random vibration theory, to earthquake high-frequency strong-motions in the South Iceland Seismic Zone. The SBM is used as it provides a physically consistent and efficient description of the heterogeneous faulting processes that are responsible for the generation of high-frequency waves. On the basis of the concise point-source representation of radiated spectra from N subevents of the SBM the pseudo-spectral accelerations were modeled and compared with that of data in the spectral domain. Backwards model selection was then carried out using Bayesian inference with Monte Carlo simulations and Markov Chains. The number of parameters in the model inference was reduced to obtain stable Markov chains and posterior probability density functions for each parameter, eliminating parametric cross-correlations to the extent possible. The seismological model has been shown to be unbiased with respect to strong-motions in the SISZ, with a total standard deviation of 0.216 (common logarithm), with only a minor contribution from inter-event variability, suggesting a relatively uniform character of SISZ earthquake strong-motions. We showcase the application of the SBM extended into a finite-fault and model the three M w 6.3 - 6.5 earthquakes in the dataset, allowing subevents of varying sizes to populate the fault plane and provide a more realistic earthquake source and acceleration ground motion time history modeling. The time domain results are shown to capture the essential characteristics of the ground motions of the three largest earthquakes in the dataset. We present therefore the SBM as a physically consistent source model of SISZ earthquakes for the generation of synthetic strong-motion time histories or peak parameters, with potential applications in scenario simulations and probabilistic or deterministic seismic hazard assessment. • Stochastic earthquake source model can simulate f > 1 Hz ground motion in South Iceland. • Bayesian inference on seismological model parameters yields uncertainty estimates. • Step-by-step model selection shows influence of fixing model parameter values. • Extension from point-source to finite fault stochastic model can improve data fit. • Specific Barrier Model allows physically consistent extension from point to finite fault. [ABSTRACT FROM AUTHOR]

• PHiD-CV was introduced without catch-up in Iceland in 2011 and achieved >97% uptake. • Population based study following 11 consecutive birth-cohorts until 3 years of age. • Cox regression model of hospitalizations for respiratory and invasive infections. • IPD hospitalizations decreased by 93% while vaccine-type IPD decreased by 100%. • Pneumonia admissions decreased by 20% despite 32% increase in bronchiolitis. Pneumococcus is an important respiratory pathogen. The 10-valent pneumococcal vaccine (PHiD-CV) was introduced into the Icelandic vaccination programme in 2011. The aim was to estimate the impact of PHiD-CV on paediatric hospitalisations for respiratory tract infections and invasive disease. The 2005–2015 birth-cohorts were followed until three years of age and hospitalisations were recorded for invasive pneumococcal disease (IPD), meningitis, sepsis, pneumonia and otitis media. Hospitalisations for upper- and lower respiratory tract infections (URTI, LRTI) were used as comparators. The 2005–2010 birth-cohorts were defined as vaccine non-eligible cohorts (VNEC) and 2011–2015 birth-cohorts as vaccine eligible cohorts (VEC). Incidence rates (IR) were estimated for diagnoses, birth-cohorts and age groups, and incidence rate ratios (IRR) between VNEC and VEC were calculated assuming Poisson variance. Cox regression was used to estimate the hazard ratio (HR) of hospitalisation between VNEC and VEC. 51,264 children were followed for 142,315 person-years, accumulating 1,703 hospitalisations for the respective study diagnoses. Hospitalisations for pneumonia decreased by 20% (HR 0.80, 95%CI:0.67–0.95) despite a 32% increase in admissions for LRTI (HR 1.32, 95%CI:1.14–1.53). Hospital admissions for culture-confirmed IPD decreased by 93% (HR 0.07, 95%CI:0.01–0.50) and no hospitalisations for IPD with vaccine-type pneumococci were observed in the VEC. Hospitalisations for meningitis and sepsis did not change. A decrease in hospital admissions for otitis media was observed, but did not coincide with PHiD-CV introduction. Following the introduction of PHiD-CV in Iceland, hospitalisations for pneumonia and culture confirmed IPD decreased. Admissions for other LRTIs and URTIs increased during this period. [ABSTRACT FROM AUTHOR]

Background: Air pollutants in Iceland's capital area include hydrogen sulfide (H2S) emissions from geothermal power plants, particle pollution (PM10) and traffic-related pollutants. Respiratory health effects of exposure to PM and traffic pollutants are well documented, yet this is one of the first studies to investigate short-term health effects of ambient H2S exposure. Objectives: The aim of this study was to investigate the associations between daily ambient levels of H2S, PM10, nitrogen dioxide (NO2) and ozone (O3), and the use of drugs for obstructive pulmonary diseases in adults in Iceland's capital area. Methods: The study period was 8 March 2006 to 31 December 2009. We used log-linear Poisson generalized additive regression models with cubic splines to estimate relative risks of individually dispensed drugs by air pollution levels. A three-day moving average of the exposure variables gave the best fit to the data. Final models included significant covariates adjusting for climate and influenza epidemics, as well as time-dependent variables. Results: The three-day moving average of H2S and PM10 levels were positively associated with the number of individuals who were dispensed drugs at lag 3–5, corresponding to a 2.0% (95% confidence interval [CI] 0.4, 3.6) and 0.9% (95% CI 0.1, 1.8) per 10μg/m3 pollutant concentration increase, respectively. Conclusion: Our findings indicated that intermittent increases in levels of particle matter from traffic and natural sources and ambient H2S levels were weakly associated with increased dispensing of drugs for obstructive pulmonary disease in Iceland's capital area. These weak associations could be confounded by unevaluated variables hence further studies are needed. [Copyright &y& Elsevier]

The Icelandic strong-motion dataset is relatively small and the largest recorded earthquake magnitude is M w 6.5, whereas events of around M w 7.0 are known to have occurred in the South Iceland Seismic Zone (SISZ). As a result, the required features for use in probabilistic seismic hazard assessment (PSHA), such as deviation from self-similar magnitude scaling and magnitude-distance dependent saturation of ground motions at larger magnitudes, is challenging. Compounding the issue, GMMs from other seismic regions exhibit a strong bias to the available Icelandic strong-motions, underpredicting in the near-fault and overpredicting in the far-field regions. In this study, we approach this issue by considering several GMMs that have either been used or recommended for PSHA in Iceland or have functional forms that satisfy the minimum requirements of GMMs used in PSHA. We recalibrate these GMMs to fit the Icelandic data in the context of the Bayesian statistical framework and a Markov Chain Monte Carlo (MCMC) algorithm, where model inference is carried out using both non-informative and informative priors for selected model coefficients from the original GMMs. Moreover, we used a random effects model to partition the aleatory variability into inter-event and intra-event components. We show that the GMMs with informative priors for magnitude scaling and magnitude-distance scaling terms, not only capture the high near-fault amplitudes and rapid ground motion attenuation with distance, but also introduce a controlled saturation of large magnitude ground motions, which is consistent with observations in other interplate regions. In this study we also introduce a simple GMM, based on informative priors from a model for magnitude-dependent earthquake depth in the SISZ, that fully captures the salient characteristics of the recalibrated GMMs. The presented models thus form a suite of new, essentially hybrid, empirical GMMs that can be used with confidence in predicting PGA and PSA for Icelandic earthquakes, with particular implications for the reassessment of the seismic hazard of Iceland. • Recalibration of several ground motion models (GMMs) to the available Icelandic strong-motion data in the context of the Bayesian statistical framework and a Markov Chain Monte Carlo algorithm. • Informative priors from the original GMMs for unconstrained model parameters ensure well behaved posterior distributions and more physically realistic predictions of the recalibrated models.. • A simple GMM is introduced based on informative priors for magnitude-dependent earthquake depth in the South Iceland seismic zone, that fully captures the salient characteristics of the recalibrated GMMs. • A suite of new, essentially hybrid, empirical GMMs is presented for prediction of PGA and PSA for Icelandic earthquakes with implications forthe reassessment of the seismic hazard of Iceland. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the association of potential risk factors for urinary tract infections (UTI) caused by E. coli producing ESBL vs. not producing ESBL in Iceland., Methods: Observational, case-control study including a cohort of 27,747 patients (22,800 females, 4,947 males; 1207 cases, 26,540 controls) of all ages with UTI caused by E. coli in 2012 to 2021 at the clinical microbiology laboratory covering about 2/3 of the Icelandic population. Clinical patient data was obtained from three national databases. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) as a measure of association between ESBL and exposure variables., Results: The proportion of samples with ESBL-producing E. coli increased during the study period, from 2.6% in 2012 to 7.6% in 2021 (p < 0.001). ESBL-positive strains were detected in 1207 individuals (4.4%), 905 females (4.0%) and 302 males (6.1%). The following risk factors were identified: Male sex, higher age, institution type (hospital, nursing home), hospital-associated UTI, Charlson comorbidity index score ≥ 3, history of cystitis or hospitalization in the past year, and prescriptions for certain antibiotics or proton pump inhibitors (PPIs: OR 1.51) in the past half year. The antibiotic associated with the highest risk was ciprofloxacin (OR 2.45)., Conclusion: The prevalence of UTIs caused by ESBL-producing E. coli has been increasing in Iceland. The strongest risk factors for ESBL production were previous antibiotic use, especially ciprofloxacin, and previous PPI use, both considered to be overprescribed. It is important to promote the prudent use of these drugs., (© 2024. The Author(s).)

Vaccinations with the 10-valent pneumococcal conjugated vaccine (PHiD-CV) started in Iceland in 2011. Protein D (PD) from H. influenzae , which is coded for by the hpd gene, is used as a conjugate in the vaccine and may provide protection against PD-positive H. influenzae We aimed to evaluate the effect of PHiD-CV vaccination on H. influenzae in children, both in carriage and in acute otitis media (AOM). H. influenzae was isolated from nasopharyngeal swabs collected from healthy children attending 15 day care centers in 2009 and from 2012 to 2017 and from middle ear (ME) samples from children with AOM collected from 2012 to 2017. All isolates were identified using PCR for the hpd and fucK genes. Of the 3,600 samples collected from healthy children, 2,465 were culture positive for H. influenzae (68.5% carriage rate); of these, 151 (6.1%) contained hpd -negative isolates. Of the 2,847 ME samples collected, 889 (31.2%) were culture positive for H. influenzae ; of these, 71 (8.0%) were hpd negative. Despite the same practice throughout the study, the annual number of ME samples reduced from 660 in 2012 to 330 in 2017. The proportions of hpd -negative isolates in unvaccinated versus vaccinated children were 5.6% and 7.0%, respectively, in healthy carriers, and 5.4% and 7.8%, respectively, in ME samples. The proportion of hpd -negative isolates increased with time in ME samples but not in healthy carriers. The number of ME samples from children with AOM decreased. The PHiD-CV had no effect on the proportion of the hpd gene in H. influenzae from carriage, but there was an increase in hpd -negative H. influenzae in otitis media. The proportions of hpd -negative isolates remained similar in vaccinated and unvaccinated children., (Copyright © 2019 Sveinsdóttir et al.)

The introduction of pneumococcal conjugate vaccines (PCVs) into childhood vaccination programs has reduced carriage of vaccine serotypes and pneumococcal disease. The 10-valent PCV was introduced in Iceland in 2011. The aim of this study was to determine PCV impact on the prevalence of serotypes, genetic lineages, and antimicrobial-resistant pneumococci isolated from the lower respiratory tract (LRT) of adults. Pneumococci isolated between 2009 and 2017 at the Landspitali University Hospital were included ( n  = 797). The hospital serves almost three-quarters of the Icelandic population. Isolates were serotyped and tested for antimicrobial susceptibility, and the genome of every other isolate collected between 2009 and 2014 was sequenced ( n  = 275). Serotypes and multilocus sequence types (STs) were extracted from the genome data. Three study periods were defined, 2009 to 2011 (PreVac), 2012 to 2014 (PostVac-I), and 2015 to 2017 (PostVac-II). The total number of isolates and vaccine-type (VT) pneumococci decreased from PreVac to PostVac-II ( n  = 314 versus n  = 230 [ p  = 0.002] and n  = 170 versus n  = 33 [ p  < 0.001], respectively), but non-vaccine-type (NVT) pneumococci increased among adults 18 to 64 years old ( n  = 56 versus n  = 114 [ p  = 0.008]). Serotype 19F decreased in the PostVac-II period; these isolates were all multidrug resistant (MDR) and were members of the Taiwan 19F -14 PMEN lineage. Serotype 6A decreased among adults ≥65 years old in the PostVac-II period ( p  = 0.037), while serotype 6C increased ( p  = 0.021) and most serotype 6C isolates were MDR. Nonencapsulated Streptococcus pneumoniae (NESp) isolates increased among adults 18 to 64 years old in the PostVac-II period, and the majority were MDR ( p  = 0.028). An overall reduction in the number of LRT samples and pneumococcus-positive cultures and significant changes in the serotype distribution became evident within 4 years, thereby demonstrating a significant herd effect., (Copyright © 2019 Quirk et al.)

Vaccination with pneumococcal conjugate vaccines (PCVs) disrupts the pneumococcal population. Our aim was to determine the impact of the 10-valent PCV on the serotypes, genetic lineages, and antimicrobial susceptibility of pneumococci isolated from children in Iceland. Pneumococci were collected between 2009 and 2017 from the nasopharynges of healthy children attending 15 day care centers and from the middle ears (MEs) of children with acute otitis media from the greater Reykjavik capital area. Isolates were serotyped and tested for antimicrobial susceptibility. Whole-genome sequencing (WGS) was performed on alternate isolates from 2009 to 2014, and serotypes and multilocus sequence types (STs) were extracted from the WGS data. Two study periods were defined: 2009 to 2011 (PreVac) and 2012 to 2017 (PostVac). The overall nasopharyngeal carriage rate was similar between the two periods (67.3% PreVac and 61.5% PostVac, P = 0.090). Vaccine-type (VT) pneumococci decreased and nonvaccine-type (NVT) pneumococci (serotypes 6C, 15A, 15B/C, 21, 22F, 23A, 23B, 35F, and 35B) significantly increased in different age strata post-PCV introduction. The total number of pneumococci recovered from ME samples significantly decreased as did the proportion that were VTs, although NVT pneumococci (6C, 15B/C, 23A, and 23B) increased significantly. Most serotype 6C pneumococci were multidrug resistant (MDR). Serotype 19F was the predominant serotype associated with MEs, and it significantly decreased post-PCV introduction: these isolates were predominantly MDR and of the Taiwan 19F -14 PMEN lineage. Overall, the nasopharyngeal carriage rate remained constant and the number of ME-associated pneumococci decreased significantly post-PCV introduction; however, there was a concomitant and statistically significant shift from VTs to NVTs in both collections of pneumococci., (Copyright © 2018 Quirk et al.)

Background: The 10-valent pneumococcal conjugate vaccine (PHiD-CV10) was introduced in Iceland in 2011, without catch-up. The aim of this study was to estimate vaccine impact (VI) on acute otitis media (AOM)., Methods: In this whole-population study, all primary care visits due to AOM from 2005 to 2015 in children <3 years of age were included. Birth cohorts were grouped as vaccine noneligible (VNEC) or vaccine eligible (VEC). Crude incidence rates (IRs) were compared between the VNEC and VEC. A Cox regression model for repeated events was used to model the individual-level data. VI was calculated as (hazard ratio [HR] - 1) × 100%., Results: Included were 53150 children, with 140912 person-years of follow-up and 58794 AOM episodes. Both IR and the mean number of episodes differed significantly between VNEC and VEC; 43 compared to 38 episodes per 100 person-years and 1.61 episodes per child compared to 1.37. IR was significantly reduced in all age brackets, with the largest reduction in children <4 months of age (40% [95% confidence interval {CI}, 31%-49%). The VI on all-cause AOM was 22% (95% CI, 12%-31%). The impact was mediated through its effect on the first (HR, 0.84 [95% CI, .82-.86]) and second (HR, 0.95 [95% CI, .93-.98]) episodes., Conclusions: The impact of PHiD-CV10 on all-cause AOM was considerable, mediated mainly by preventing the first two episodes of AOM. A decrease in the IR of AOM in children too young to receive direct vaccine protection was demonstrated, suggesting herd effect.

Background: Acute otitis media (AOM) nonresponsive to antibiotics is most commonly caused by antibiotic-resistant Streptococcus pneumoniae and Haemophilus influenzae. A strategy for treating these infections with parenteral ceftriaxone was adopted at the Children's Hospital Iceland. The 10-valent pneumococcal H. influenzae protein D-conjugate vaccine was introduced into the vaccination program in Iceland in 2011. The aim was to study its effect on the incidence of AOM with treatment failure., Methods: This retrospective observational study included children who visited the Children's Hospital Iceland because of AOM or received ceftriaxone, regardless of indication from 2008-2015. Incidence rate was calculated for prevaccine (2008-2011) and postvaccine (2012-2015) periods using person-years at risk within the hospital's referral region. Incidence rate ratio of ceftriaxone treatment episodes of AOM was calculated using the Mantel-Haenzel method adjusting for age. Incidence risk ratio of ceftriaxone treatment if presenting to the hospital with AOM was calculated to adjust for rate of AOM visits., Results: Visits for AOM decreased from 47.5 to 33.9 visits per 1000 person-years, incidence rate ratio (IRR) 0.86 (95% confidence interval [CI]: 0.81-0.91), P < 0.001. Fewer AOM episodes were treated with ceftriaxone, decreasing from 6.49 to 2.96 treatment episodes per 1000 person-years, with an overall Mantel-Haenzel adjusted IRR 0.45 (95% CI: 0.37-0.54; P < 0.001). This remained significant after adjusting for the decrease in AOM visits, IRR 0.53 (95% CI: 0.44-0.63; P < 0.001)., Conclusions: Visits for AOM and ceftriaxone use decreased significantly after H. influenzae protein D-conjugate vaccine introduction. The observed decrease in ceftriaxone use is presumed to represent a decline in AOM with treatment failure, secondary to a decrease in resistant infections.

Objectives: The needs of patients with uncompleted visits to the emergency department (ED) are uncertain. The aim was to evaluate ED patients who leave against medical advice (AMA) and who leave without being seen (WBS) regarding repeat ED visits, hospitalisation and mortality within 30 days., Methods: The National University Hospital operates the only ED for adults in the capital area of Reykjavik. The source of data was the electronic records for patients 18 years or older, who left AMA, who left WBS, who had the ICD-10 code Z53.2, or who completed their visits. ED visits, hospital admissions and the death registry are filed with the personal identification number, which enabled recognition of the index visit, and the outcomes, rates of return visits, hospitalisation and death., Results: Of 107 119 patients, 77 left AMA, 4471 left WBS and 423 had code Z53.2. The HR for returning to the ED within 30 days was 4.79 for AMA patients, 4.84 for WBS patients and 3.67 for Z53.2 patients. The HR for hospitalisation within 30 days was 6.90 for AMA patients, 1.09 for WBS patients and 1.07 for Z53.2 patients. The HR for death within 30 days was 10.97 for AMA patients, 0.84 for WBS and no deaths occurred among Z53.2 patients., Discussion: During 30 days follow-up, AMA and WBS patients had an increased rate of repeat ED visits compared with those patients who completed their ED visits. AMA patients also had an increased rate of hospitalisations.

Background: Day care attendance is a major risk factor for respiratory and gastrointestinal illnesses in preschool children. In this study, we describe the results of a hygiene intervention cohort trial at day care centres (DCCs) on the rates of febrile, respiratory, and gastrointestinal illnesses in preschool children., Methods: Thirty DCCs in 2 communities were included. The number of illness episodes was registered for each child every 6 months, as well as potential risk factors. The hygiene intervention was introduced in half of the DCCs and the results analysed using a multivariate mixed effects hierarchical Poisson regression model., Results: The study lasted 2.5 y, of which the hygiene intervention lasted 1.5 y. Two thousand three hundred and forty-nine children participated, delivering 2832 person-y. Adjusted incidence rate ratios of the illnesses at the intervention and non-intervention DCCs were not significantly different for any of the illnesses. The intervention was not more effective in children less than 3 y of age than in older children and no significant effects were seen with time. Compliance with the hygiene protocol was good as measured by the use of hygiene products and by a survey among the staff at the DCCs., Conclusions: The most likely explanation for the lack of effects of the intervention is that the baseline standard of hygiene at the DCCs was probably too high for the intervention to demonstrate significant results, but recall bias cannot be excluded. Even though hygiene is important for minimizing the spread of microbes at DCCs, other risk factors need to be studied.

We propose two methods to evaluate the statistical significance of differences in linkage disequilibrium (LD) between populations, where LD is measured by the standardised parameter D'. The first method is based on bootstrapping individuals within populations in order to test LD differences for each pair of loci. Using this approach we propose a solution to the problem of testing multiple locus-pairs by means of a single test for the number of pairs that exhibit significant LD differences among populations. The second method provides the Bayesian posterior probability that one population has greater LD than the other for each locus pair. Both methods can handle genotypes with unknown phase, and are demonstrated using two data sets. For the purpose of demonstration, we apply the methods to two different sets of data from humans. First, we explore the issue of LD differences between reproductively isolated populations using a new data set of twelve Xq25 microsatellites, typed in four European populations. Second, we examine evidence for LD differences between Alzheimer cases and controls from the Icelandic population using 19 single nucleotide polymorphisms (SNPs) from a 97 kb region flanking the Apolipoprotein E (APOE) gene on chromosome 19.

Objective: The aim of this study was to investigate psychotropic drug use among children in Iceland between 2003 and 2007., Methods: A nationwide population-based drug use study covering the total pediatric population (ages 0-17) in Iceland. Information was obtained from the National Medicines Registry to calculate prevalence of use by year and psychotropic drug group; incidence by year, psychotropic drug group, child's age and sex, and medical specialty of prescriber; the most commonly used psychotropic chemical substances, off-label and unlicensed use and concomitant psychotropic drug use., Results: The overall prevalence of psychotropic drug use was 48.7 per 1000 Icelandic children in 2007. Stimulants and antidepressants increased in prevalence from 2003 to 2007 and were the two most prevalent psychotropic drug groups, respectively, 28.4 and 23.4 per 1000 children in 2007. A statistically significant trend of declining prevalence (p = 0.00013) and incidence (p = 0.0018) of antidepressant use occurred during the study period. Out of 21,986 psychotropic drugs dispensed in 2007, 25.4% were used off-label., Conclusions: With reference to reports from other European countries, the results indicate extensive psychotropic drug use among children in Iceland between 2003 and 2007. Further scrutiny is needed to assess the rationale behind this widespread use.

The impact of population structure on association studies undertaken to identify genetic variants underlying common human diseases is an issue of growing interest. Spurious associations of alleles with disease phenotypes may be obtained or true associations overlooked when allele frequencies differ notably among subpopulations that are not represented equally among cases and controls. Population structure influences even carefully designed studies and can affect the validity of association results. Most study designs address this problem by sampling cases and controls from groups that share the same nationality or self-reported ethnic background, with the implicit assumption that no substructure exists within such groups. We examined population structure in the Icelandic gene pool using extensive genealogical and genetic data. Our results indicate that sampling strategies need to take account of substructure even in a relatively homogenous genetic isolate. This will probably be even more important in larger populations.

Historical inferences from genetic data increasingly depend on assumptions about the genealogical process that shapes the frequencies of alleles over time. Yet little is known about the structure of human genealogies over long periods of time and how they depart from expectations of standard demographic models, such as that attributed to Wright and Fisher. To obtain such information and to examine the recent evolutionary history of mtDNA and Y-chromosome haplotypes in the Icelandic gene pool, we traced the matrilineal and patrilineal ancestry of all 131,060 Icelanders born after 1972 back to two cohorts of ancestors, one born between 1848 and 1892 and the other between 1798 and 1742. This populationwide coalescent analysis of Icelandic genealogies revealed highly positively skewed distributions of descendants to ancestors, with the vast majority of potential ancestors contributing one or no descendants and a minority of ancestors contributing large numbers of descendants. The expansion and loss of matrilines and patrilines has caused considerable fluctuation in the frequencies of mtDNA and Y-chromosome haplotypes, despite a rapid population expansion in Iceland during the past 300 years. Contrary to a widespread assumption, the rate of evolution caused by this lineage-sorting process was markedly faster in matrilines (mtDNA) than in patrilines (Y chromosomes). The primary cause is a 10% shorter matrilineal generation interval. Variance in the number of offspring produced within each generation was not an important differentiating factor. We observed an intergenerational correlation in offspring number and in the length of generation intervals in the matrilineal and patrilineal genealogies, which was stronger in matrilines and thus contributes to their faster evolutionary rate. These findings may have implications for coalescent date estimates based on mtDNA and Y chromosomes.