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Background: There is increasing interest in the development of statistical models that can be used to estimate risk of adverse patient outcomes after joint arthroplasty. Competing risk approaches have been recommended to estimate risk of longer-term revision, which is often likely to be precluded by the competing risk of death. However, a common approach is to ignore the competing risk by treating death as a censoring event and using standard survival models such as Cox regression. It is well-known that this approach can overestimate the event risk for population-level estimates, but the impact on the estimation of a patient's individualized risk after joint arthroplasty has not been explored.Questions/purposes: We performed this study to (1) determine whether using a competing risk or noncompeting risk method affects the accuracy of predictive models for joint arthroplasty revision and (2) determine the magnitude of difference that using a competing risks versus noncompeting risks approach will make to predicted risks for individual patients.Methods: The predictive performance of a standard Cox model, with competing risks treated as censoring events, was compared with the performance of two competing risks approaches, the cause-specific Cox model and Fine-Gray model. Models were trained and tested using data pertaining to 531,304 TKAs and 274,618 THAs recorded in the Australian Orthopaedic Association National Joint Replacement Registry between January 1, 2003 and December 31, 2017. The registry is a large database with near-complete capture and follow-up of all hip and knee joint arthroplasty in Australia from 2003 onwards, making it an ideal setting for this study. The performance of the three modeling approaches was compared in two different prediction settings: prediction of the 10-year risk of all-cause revision after TKA and prediction of revision for periprosthetic fracture after THA. The calibration and discrimination of each approach were compared using the concordance index, integrated Brier scores, and calibration plots. Calibration of 10-year risk estimates was further assessed within subgroups of age by comparing the observed and predicted proportion of events. Estimated 10-year risks from each model were also compared in three hypothetical patients with different risk profiles to determine whether differences in population-level performance metrics would translate into a meaningful difference for individual patient predictions.Results: The standard Cox and two competing risks models showed near-identical ability to distinguish between high-risk and low-risk patients (c-index 0.64 [95% CI, 0.64 to 0.64] for all three modeling approaches for TKAs and 0.66 [95% CI 0.66 to 0.66] for THA). All models performed similarly in patients younger than 75 years, but for patients aged 75 years and older, the standard Cox model overestimated the risk of revision more than the cause-specific Cox and Fine-Gray model did. These results were echoed when predictions were made for hypothetical individual patients. For patients with a low competing risk of mortality, the 10-year predicted risks from the standard Cox, cause-specific Cox, and Fine-Gray models were similar for TKAs and THAs. However, a larger difference was observed for hypothetical 89-year-old patients with increased mortality risk. In TKAs, the revision risk for an 89-year-old patient was so low that this difference was negligible (0.83% from the cause-specific Cox model versus 1.1% from the standard Cox model). However, for THAs, where older age is a risk factor for both death and revision for periprosthetic fracture, a larger difference was observed in the 10-year predicted risks for a hypothetical 89-year-old patient (3.4% from the cause-specific Cox model versus 5.2% from the standard Cox model).Conclusion: When developing models to predict longer-term revision of joint arthroplasty, failing to use a competing risks modeling approach will result in overestimating the revision risk for patients with a high risk of mortality during the surveillance period. However, even in an extreme instance, where both the frequency of the event of interest and the competing risk of death are high, the largest absolute difference in predicted 10-year risk for an individual patient was just 1.8%, which may not be of consequence to an individual. Despite these findings, when developing or using risk prediction models, researchers and clinicians should be aware of how competing risks were handled in the modeling process, particularly if the model is intended for use populations where the mortality risk is high.Level Of Evidence: Level III, therapeutic study. [ABSTRACT FROM AUTHOR]

Background: Microbial exposures in utero and early life shape the infant microbiome, which can profoundly impact on health. Compared to the bacterial microbiome, very little is known about the virome. We set out to characterize longitudinal changes in the gut virome of healthy infants born to mothers with or without type 1 diabetes using comprehensive virome capture sequencing. Methods: Healthy infants were selected from Environmental Determinants of Islet Autoimmunity (ENDIA), a prospective cohort of Australian children with a first‐degree relative with type 1 diabetes, followed from pregnancy. Fecal specimens were collected three‐monthly in the first year of life. Results: Among 25 infants (44% born to mothers with type 1 diabetes) at least one virus was detected in 65% (65/100) of samples and 96% (24/25) of infants during the first year of life. In total, 26 genera of viruses were identified and >150 viruses were differentially abundant between the gut of infants with a mother with type 1 diabetes vs without. Positivity for any virus was associated with maternal type 1 diabetes and older infant age. Enterovirus was associated with older infant age and maternal smoking. Conclusions: We demonstrate a distinct gut virome profile in infants of mothers with type 1 diabetes, which may influence health outcomes later in life. Higher prevalence and greater number of viruses observed compared to previous studies suggests significant underrepresentation in existing virome datasets, arising most likely from less sensitive techniques used in data acquisition. [ABSTRACT FROM AUTHOR]

Objectives: Given increasing frequency of heatwaves and growing public health concerns associated with foodborne disease, we examined the relationship between heatwaves and salmonellosis in Adelaide, Australia.Methods: Poisson regression analysis with Generalised Estimating Equations was used to estimate the effect of heatwaves and the impact of intensity, duration and timing on salmonellosis and specific serotypes notified from 1990 to 2012. Distributed lag non-linear models were applied to assess the non-linear and delayed effects of temperature during heatwaves on Salmonella cases.Results: Salmonella typhimurium PT135 notifications were sensitive to the effects of heatwaves with a twofold (IRR 2.08, 95% CI 1.14-3.79) increase in cases relative to non-heatwave days. Heatwave intensity had a significant effect on daily counts of overall salmonellosis with a 34% increase in risk of infection (IRR 1.34, 95% CI 1.01-1.78) at >41 °C. The effects of temperature during heatwaves on Salmonella cases and serotypes were found at lags of up to 14 days.Conclusion: This study confirms heatwaves have a significant effect on Salmonella cases, and for the first time, identifies its impact on specific serotypes and phage types. These findings will contribute to the understanding of the impact of heatwaves on salmonellosis and provide insights that could mitigate their impact. [ABSTRACT FROM AUTHOR]

Background: Fertility treatment is associated with increased risk of major birth defects, which varies between in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI), and is significantly reduced by embryo freezing. We therefore examined a range of additional perinatal outcomes for these exposures. Methods: All patients in South Australia receiving assisted conception between Jan 1986–Dec 2002 were linked to the state-wide perinatal collection (all births/stillbirths ≥20 weeks gestation or 400 g birth weight, n = 306 995). We examined stillbirth, mean birth weight, low birth weight (<2500 g, <1500 g), small size for gestational age (<10th percentile, <3rd percentile), large size for gestational age (>90th percentile), preterm birth (32–<37 weeks, <32 weeks gestation), postterm birth (≥41 weeks gestation), Apgar <7 at 5 minutes and neonatal death. Results: Relative to spontaneous conceptions, singletons from assisted conception were more likely to be stillborn (OR = 1.82, 95% Confidence Interval (CI) 1.34–2.48), while survivors as a group were comprehensively disadvantaged at birth, including lower birth weight (−109 g, CI −129–−89), very low birth weight (OR = 2.74, CI 2.19–3.43), very preterm birth (OR = 2.30, CI 1.82–2.90) and neonatal death (OR = 2.04, CI 1.27–3.26). Outcomes varied by type of assisted conception. Very low and low birth weight, very preterm and preterm birth, and neonatal death were markedly more common in singleton births from IVF and to a lesser degree, in births from ICSI. Using frozen-embryos eliminated all significant adverse outcomes associated with ICSI but not with IVF. However, frozen-embryo cycles were also associated with increased risk of macrosomia for IVF and ICSI singletons (OR = 1.36, CI 1.02–1.82; OR = 1.55, CI 1.05–2.28). Infertility status without treatment was also associated with adverse outcomes. Conclusions: Births after assisted conception show an extensive range of compromised outcomes that vary by treatment modality, that are substantially reduced after embryo freezing, but which co-occur with an increased risk of macrosomia. [ABSTRACT FROM AUTHOR]

The purpose was to examine the relationship between different types of social networks and memory over 15 years of followup in a large cohort of older Australians who were cognitively intact at study baseline. Our specific aims were to investigate whether social networks were associated with memory, determine if different types of social networks had different relationships with memory, and examine if changes in memory over time differed according to types of social networks. We used five waves of data from the Australian Longitudinal Study of Ageing, and followed 706 participants with an average age of 78.6 years (SD 5.7) at baseline. The relationships between five types of social networks and changes in memory were assessed. The results suggested a gradient of effect; participants in the upper tertile of friends or overall social networks had better memory scores than those in the mid tertile, who in turn had better memory scores than participants in the lower tertile. There was evidence of a linear, but not quadratic, effect of time on memory, and an interaction between friends' social networks and time was apparent. Findings are discussed with respect to mechanisms that might explain the observed relationships between social networks and memory. [ABSTRACT FROM AUTHOR]

Background: While menarche indicates the beginning of a woman's reproductive life, relatively little is known about the association between age at menarche and subsequent morbidity and mortality. We aimed to examine the effect of lower age at menarche on all-cause mortality in older Australian women over 15 years of follow-up.Methods: Data were drawn from the Australian Longitudinal Study of Ageing (n = 1,031 women aged 65-103 years). We estimated the hazard ratio (HR) associated with lower age at menarche using Cox proportional hazards models, and adjusted for a broad range of reproductive, demographic, health and lifestyle covariates.Results: During the follow-up period, 673 women (65%) died (average 7.3 years (SD 4.1) of follow-up for decedents). Women with menses onset < 12 years of age (10.7%; n = 106) had an increased hazard of death over the follow-up period (adjusted HR 1.28; 95%CI 0.99-1.65) compared with women who began menstruating aged >or= 12 years (89.3%; n = 883). However, when age at menarche was considered as a continuous variable, the adjusted HRs associated with the linear and quadratic terms for age at menarche were not statistically significant at a 5% level of significance (linear HR 0.76; 95%CI 0.56 - 1.04; quadratic HR 1.01; 95%CI 1.00-1.02).Conclusion: Women with lower age at menarche may have reduced survival into old age. These results lend support to the known associations between earlier menarche and risk of metabolic disease in early adulthood. Strategies to minimise earlier menarche, such as promoting healthy weights and minimising family dysfunction during childhood, may also have positive longer-term effects on survival in later life. [ABSTRACT FROM AUTHOR]

To report on the validity of the Nursing Home Behaviour Problem Scale (NHBPS) in an Australian residential care setting.Cluster randomised controlled trial. As part of this, questionnaires were administered to residential care staff concerning participating residents. The study was carried out in 20 residential care facilities (10 hostels, 10 nursing homes) in metropolitan Adelaide, South Australia. Staff closely associated with the resident's care completed 694 questionnaires. Internal consistency of the scale was examined along with exploratory and confirmatory factor analysis to determine the validity of the NHBPS in the Australian setting.Analyses indicated that four of the 29 questions should be excluded from the Australian version of the NHBPS. Factor analysis demonstrated five factors accounting for 25 of the questions, grouped around behaviours of uncooperative, inappropriate, attention seeking, unsafe, and agitation.There is a need for patient-specific outcome measures, particularly measuring difficult behaviours, for use in residential care settings. Despite the similarities in the prevalence of disturbed behaviours, we were unable to reproduce the six factors reported in the original validation of the instrument, possibly due to differences between the USA and Australia. The results indicate the number of questions should be reduced to 25 in the Australian version of the NHBPS. [ABSTRACT FROM AUTHOR]

OBJECTIVES: Older people are at risk of undernutrition because of a number of physiological conditions and lifestyle factors. The purpose of this study was to explore the predictive relationship of corrected arm muscle area (CAMA) with 8-year mortality in a representative sample of older Australians. DESIGN: Prospective cohort study: The Australian Longitudinal Study of Ageing. SETTING: Community. PARTICIPANTS: One thousand three hundred ninety-six participants aged 70 and older. MEASUREMENTS: Trained observers measured baseline weight, height, mid upper arm circumference, and triceps skinfold thickness using standard techniques. Body mass index (BMI) and CAMA were calculated. Baseline BMI and CAMA measurements were categorized according to cutoff values proposed by Garrow et al. and Friedman et al., respectively. Subsequent analyses were undertaken using Cox proportional hazards regression. RESULTS: After adjustment for potential confounders (baseline age, gender, marital status, smoking, self-rated health, ability to conduct activities of daily living, comorbidity, cognition performance, and presence of depression), those older Australians with a low CAMA (≤21.4 cm2 for men and ≤21.6 cm2 for women) had an increased risk of mortality at 8-year follow-up (hazard ratio = 1.94, 95% confidence interval = 1.25–3.00, P = .003). There was no increased risk in 8-year mortality identified for those with a high or low BMI. CONCLUSION: CAMA is a useful assessment of undernutrition in older adults that has better prognostic value than BMI in predicting death in older, community-living Australians. [ABSTRACT FROM AUTHOR]

Increased risk of occupational injuries and illnesses (OI) is associated with ambient temperature. However, most studies have reported the average impacts within cities, states, or provinces at broader scales. We assessed the intra-urban risk of OI associated with ambient temperature in three Australian cities at statistical area level 3 (SA3). We collected daily workers' compensation claims data and gridded meteorological data from July 1, 2005, to June 30, 2018. Heat index was used as the primary temperature metric. We performed a two-stage time series analysis: we generated location-specific estimates using Distributed Lag Non-Linear Models (DLNM) and estimated the cumulative effects with multivariate meta-analysis. The risk was estimated at moderate heat (90th percentile) and extreme heat (99th percentile). Subgroup analyses were conducted to identify vulnerable groups of workers. Further, the OI risk in the future was estimated for two projected periods: 2016–2045 and 2036–2065. The cumulative risk of OI was 3.4% in Greater Brisbane, 9.5% in Greater Melbourne, and 8.9% in Greater Sydney at extreme heat. The western inland regions in Greater Brisbane (17.4%) and Greater Sydney (32.3%) had higher risk of OI for younger workers, workers in outdoor and indoor industries, and workers reporting injury claims. The urbanized SA3 regions posed a higher risk (19.3%) for workers in Greater Melbourne. The regions were generally at high risk for young workers and illness-related claims. The projected risk of OI increased with time in climate change scenarios. This study provides a comprehensive spatial profile of OI risk associated with hot weather conditions across three cities in Australia. Risk assessment at the intra-urban level revealed strong spatial patterns in OI risk distribution due to heat exposure. These findings provide much-needed scientific evidence for work, health, and safety regulators, industries, unions, and workers to design and implement location-specific preventative measures. • Western inland regions of Sydney and Brisbane are at greater risk of OI for workers. • Workers in regions with low NDVI and socio-economic status are vulnerable to heat. • Projected climate change (2016–3045, 2036–2065) will heighten heat-related OI risk. • Location-specific risk estimation of OI is crucial to mitigate the impacts of heat. [ABSTRACT FROM AUTHOR]

Invasive meningococcal disease causes significant morbidity and mortality worldwide, with serogroup B being one of the predominant serogroups in Australia for many years. The South Australian (SA) State Government recently funded the introduction of a 4CMenB vaccination program for infants, children and adolescents. In addition to protecting against invasive meningococcal disease, emerging evidence suggests the 4CMenB vaccine may also be effective against gonorrhoea due to genetic similarities between Neisseria meningitidis and Neisseria gonorrhoeae . The proposed project aims to evaluate the effectiveness of the SA 4CMenB vaccination program against invasive meningococcal disease and gonorrhoea through a combination of observational studies using routine surveillance and research data. The main methodological approaches involve an interrupted time series regression model, screening, and case-control analyses with different sets of controls to estimate vaccine impact and effectiveness. These analyses are designed to minimize potential biases inherent in all observational studies and to provide critical data on the effectiveness of the 4CMenB vaccine against two diseases of major global public health concern.

Background: The link between heat exposure and adverse health outcomes in workers is well documented and a growing body of epidemiological evidence from various countries suggests that extreme heat may also contribute to increased risk of occupational injuries (OI). Previously, there have been no comparative reviews assessing the risk of OI due to extreme heat within a wide range of global climate zones. The present review therefore aims to summarise the existing epidemiological evidence on the impact of extreme heat (hot temperatures and heatwaves (HW)) on OI in different climate zones and to assess the individual risk factors associated with workers and workplace that contribute to heat-associated OI risks., Methods: A systematic review of published peer-reviewed articles that assessed the effects of extreme heat on OI among non-military workers was undertaken using three databases (PubMed, Embase and Scopus) without temporal or geographical limits from database inception until July 2020. Extreme heat exposure was assessed in terms of hot temperatures and HW periods. For hot temperatures, the effect estimates were converted to relative risks (RR) associated with 1 °C increase in temperature above reference values, while for HW, effect estimates were RR comparing heatwave with non-heatwave periods. The patterns of heat associated OI risk were investigated in different climate zones (according to Köppen Geiger classification) based on the study locations and were estimated using random-effects meta-analysis models. Subgroup analyses according to workers' characteristics (e.g. gender, age group, experience), nature of work (e.g. physical demands, location of work i.e. indoor/outdoor) and workplace characteristics (e.g. industries, business size) were also conducted., Results: A total of 24 studies published between 2005 and 2020 were included in the review. Among these, 22 studies met the eligibility criteria, representing almost 22 million OI across six countries (Australia, Canada, China, Italy, Spain, and USA) and were included in the meta-analysis. The pooled results suggested that the overall risk of OI increased by 1% (RR 1.010, 95% CI: 1.009-1.011) for 1 °C increase in temperature above reference values and 17.4% (RR 1.174, 95% CI: 1.057-1.291) during HW. Among different climate zones, the highest risk of OI during hot temperatures was identified in Humid Subtropical Climates (RR 1.017, 95% CI: 1.014-1.020) followed by Oceanic (RR 1.010, 95% CI: 1.008-1.012) and Hot Mediterranean Climates (RR 1.009, 95% CI: 1.008-1.011). Similarly, Oceanic (RR 1.218, 95% CI: 1.093-1.343) and Humid Subtropical Climates (RR 1.213, 95% CI: 0.995-1.431) had the highest risk of OI during HW periods. No studies assessing the risk of OI in Tropical regions were found. The effects of hot temperatures on the risk of OI were acute with a lag effect of 1-2 days in all climate zones. Young workers (age < 35 years), male workers and workers in agriculture, forestry or fishing, construction and manufacturing industries were at high risk of OI during hot temperatures. Further young workers (age < 35 years), male workers and those working in electricity, gas and water and manufacturing industries were found to be at high risk of OI during HW., Conclusions: This review strengthens the evidence on the risk of heat-associated OI in different climate zones. The risk of OI associated with extreme heat is not evenly distributed and is dependent on underlying climatic conditions, workers' attributes, the nature of work and workplace characteristics. The differences in the risk of OI across different climate zones and worker subgroups warrant further investigation along with the development of climate and work-specific intervention strategies., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: An increasing demand for acute care services due in part to rising proportions of older people and increasing rates of chronic diseases has led to new models of post-acute care for older people that offer coordinated discharge, ongoing support and often a focus on functional restoration. Overall, review of the literature suggests there is considerable uncertainty around the effectiveness and resource implications of the various model configurations and delivery approaches. In this paper, we review the current evidence on the efficacy of such programs, using the Australian Transition Care Program as a case study., Discussion: The Australian Transition Care Program was established at the interface of the acute and aged care sectors with particular emphasis on transitions between acute and community care. The program is intended to enable a significant proportion of care recipients to return home, rather than prematurely enter residential aged care, optimize their functional capacity, and reduce inappropriate extended lengths of hospital stay for older people. Broadly, the model is configured and targeted in accordance with programs reported in the international literature to be effective. Early evaluations suggest good acceptance of the program by hospitals, patients and staff. Ultimately, however, the program's place in the array of post-acute services should be determined by its demonstrated efficacy relative to other services which cater for similar patient groups., Summary: Currently there is a lack of robust evaluation to provide convincing evidence of efficacy, either from a patient outcome or cost reduction perspective. As the program expands and matures, there will be opportunity to scrutinise the systematic effects, with lessons for both Australian and international policy makers and clinical leaders.

Research on variables that encourage older adults to exercise is limited. This study was carried out to identify the participation motives of older Australians involved in regular exercise and sport. The 815 participants (399 men, 416 women) ranged in age from 55 to 93 years (M = 63.6, SD = 7.8) and were participating in their activities of choice at least once per week. All participants completed the Participation Motivation Questionnaire for Older Adults. The most common exercise/sport activities that participants were involved in were walking, golf, lawn bowls, tennis, and swimming. The most highly reported motives for participation were to keep healthy, liking the activity, to improve fitness, and to maintain joint mobility. Principal-components analysis of the questionnaire revealed 6 factors: social, fitness, recognition, challenge/benefits, medical, and involvement. Analyses of variance showed significant differences in reasons for participation in exercise and sport based on gender, age, education level, and occupation.

Objective: To investigate the effects of total social networks and specific social networks with children, relatives, friends, and confidants on disability in mobility and Nagi functional tasks., Methods: Six waves of data from the Australian Longitudinal Study of Ageing were used. Data came from 1,477 participants aged 70 years or older. The effects of total social networks and those with children, relatives, friends, and confidants on transitions in disability status were analyzed using binary and multinomial logistic regression., Results: After controlling for a range of health, environmental, and personal factors, social networks with relatives were protective against developing mobility disability (OR = 0.89; 95% CI = 0.79 to 1.00) and Nagi disability (OR = 0.85; 95% CI = 0.74 to 0.96). Other social subnetworks did not have a consistent effect on the development of disability., Discussion: The effects of social relationships extend beyond disability in activities of daily living. Networks with relatives protect against disability in mobility and Nagi tasks.

Objectives: To provide detailed projections for the prevalence of disability and associated common health conditions for older Australians for the period 2006-2031., Design: Secondary analyses of datasets (national 1998 Survey of Disability, Ageing and Carers; and projections of Australia's population from 2006-2031) collected by the Australian Bureau of Statistics., Outcome Measures: (i) The projected number of people with differing levels of disability (core activity restrictions in self-care, mobility or communication) up to 2031; (ii) The projected number of people with the main health conditions associated with disability in 2006 and 2031., Results: Projections indicate a 70% increase in the number of older people with profound disability over the next 30 years. The main conditions associated with profound or severe core activity restriction in older Australians are musculoskeletal, nervous system, circulatory and respiratory conditions and stroke., Conclusions: In the future, there will be many more older Australians requiring assistance because of disability. This will present a challenge to families, friends, volunteers and paid service providers. The Australian planning ratio for residential aged-care services and community aged care services should be changed to take account of the shift to an older population with greater need of support.

Objective: To evaluate, in terms of function and mobility, the predictive value of commonly adopted anthropometric 'definitions' used in the nutritional assessment of older adults, in a cohort of older Australians., Design: Prospective cohort study - Australian Longitudinal Study of Ageing (ALSA)., Setting: Adelaide, South Australia (1992-1994)., Subjects: Data were analysed from 1272 non-institutionalised (685 males, 587 females) older adults > or =70 years old in South Australia. Seven 'definitions' commonly used in the anthropometric assessment of both under- and overnutrition (including four using body mass index (BMI), waist-to-hip ratio, waist circumference and percentage weight change) were evaluated at baseline, for their ability to predict functional and mobility limitation assessed (by self-report questionnaire) at two years follow-up. All questionnaires were administered and anthropometry performed by trained investigators. The associations between the definitions and decline in mobility and physical function were evaluated over two years using multiple logistic regression., Results: A BMI >85th percentile or >30 kg m-2 or a waist circumference of >102 cm in males and >88 cm in females increased risk of functional and mobility limitations. Over two years, a loss of 10% body weight significantly increased the risk of functional and mobility limitations., Conclusion: Maintaining weight within older adults, irrespective of initial body weight, may be important in preventing functional and mobility limitations. Excessive weight is associated with an increased risk of limitation in function and mobility, both key components of health-related quality of life.

Background: The purpose of the study was to validate a set of measures of social networks that will be useful in epidemiological studies of the health of older persons., Methods: Confirmatory factor analysis was used to test a multi-dimensional model of social networks. Data were drawn from The Australian Longitudinal Study of Ageing, conducted in the greater metropolitan area of Adelaide, South Australia. Participants were 1477 persons aged > or = 70 years who lived in the community or an institution and took part in the Australian Longitudinal Study of Ageing. Social networks with children, other relatives, friends and confidants were considered. Demographic indicators of gender, age group, income, education, marital status and place of residence were also measured, and social networks were compared for categories of these variables., Results: Networks with children, relatives, friends and confidants were substantiated in these analyses. Differences in networks between categories of the demographic variables were evident., Discussion: Adoption of the proposed measures will allow greater comparability between studies of older persons. This could lead to a better understanding of the effect of specific social networks upon health.