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Background: Asthma is a common yet incompletely understood health problem associated with a high morbidity burden. A wide variety of seasonally variable environmental stimuli such as viruses and air pollution are believed to influence asthma morbidity. This study set out to examine the seasonal patterns of asthma hospitalisations in relation to age and gender for the province of Ontario over a period of 12 years.Methods: A retrospective, population-based study design was used to assess temporal patterns in hospitalisations for asthma from April 1, 1988 to March 31, 2000. Approximately 14 million residents of Ontario eligible for universal healthcare coverage during this time were included for analysis. Time series analyses were conducted on monthly aggregations of hospitalisations.Results: There is strong evidence of an autumn peak and summer trough seasonal pattern occurring every year over the 12-year period (Fisher-Kappa (FK) = 23.93, p > 0.01; Bartlett Kolmogorov Smirnov (BKS) = 0.459, p < 0.01). This pattern was observed in both sexes. However, young males (0-4 years) were hospitalised at two to three times the rate of females of the same age. Rates were much lower in the older age groups. A downward trend in asthma hospitalisations was observed in the total population over the twelve-year period (beta = -0.980, p < 0.01).Conclusions: A clear and consistent seasonal pattern was observed in this study for asthma hospitalisations. These findings have important implications for the development of effective management and prevention strategies. [ABSTRACT FROM AUTHOR]

Background: Ambient air pollution has been associated with gestational diabetes (GD), but critical windows of exposure and whether maternal pre-existing conditions and other environmental factors modify the associations remains inconclusive., Methods: We conducted a retrospective cohort study of all singleton live birth that occurred between April 1 st 2006 and March 31 st 2018 in Ontario, Canada. Ambient air pollution data (i.e., fine particulate matter with a diameter ≤ 2.5 μm (PM 2.5 ), nitrogen dioxide (NO 2 ) and ozone (O 3 )) were assigned to the study population in spatial resolution of approximately 1 km × 1 km. The Normalized Difference Vegetation Index (NDVI) and the Green View Index (GVI) were also used to characterize residential exposure to green space as well as the Active Living Environments (ALE) index to represent the active living friendliness. Multivariable Cox proportional hazards regression models were used to evaluate the associations., Results: Among 1,310,807 pregnant individuals, 68,860 incident cases of GD were identified. We found the strongest associations between PM 2.5 and GD in gestational weeks 7 to 18 (HR = 1.07 per IQR (2.7 µg/m 3 ); 95% CI: 1.02 - 1.11)). For O 3 , we found two sensitive windows of exposure, with increased risk in the preconception period (HR = 1.03 per IQR increase (7.0 ppb) (95% CI: 1.01 - 1.06)) as well as gestational weeks 9 to 28 (HR 1.08 per IQR (95% CI: 1.04 -1.12)). We found that women with asthma were more at risk of GD when exposed to increasing levels of O 3 (p- value for effect modification = 0.04). Exposure to air pollutants explained 20.1%, 1.4% and 4.6% of the associations between GVI, NDVI and ALE, respectively., Conclusion: An increase of PM 2.5 exposure in early pregnancy and of O 3 exposure during late first trimester and over the second trimester of pregnancy were associated with gestational diabetes whereas exposure to green space may confer a protective effect., (© 2023. Crown.)

Background: Several studies have found positive associations between outdoor fine particulate air pollution (≤2.5 μm, PM 2.5 ) and childhood asthma incidence. However, the impact of PM 2.5 composition on children's respiratory health remains uncertain., Objective: We examined whether joint exposure to PM 2.5 mass concentrations and its major chemical components was associated with childhood asthma development., Methods: We conducted a population-based cohort study by identifying 1,130,855 singleton live births occurring between 2006 and 2014 in the province of Ontario, Canada. Concentrations of PM 2.5 and its seven major chemical components were assigned to participants based on their postal codes using chemical transport models and remote sensing. The joint impact of outdoor PM 2.5 concentrations and its major components and childhood asthma incidence (up to age 6) were estimated using Cox proportional hazards models, allowing for potential nonlinearity., Results: We identified 167,080 children who developed asthma before age 6. In adjusted models, outdoor PM 2.5 mass concentrations during childhood were associated with increased incidence of childhood asthma (Hazard Ratio (HR) for each 1 μg/m 3 increase = 1.026, 95% CI: 1.021-1.031). We found that the joint effects of PM 2.5 and its components on childhood asthma incidence may be 24% higher than the conventional approach. Specific components/source markers such as black carbon, ammonium, and nitrate appeared to play an important role., Conclusions: Early life exposure to PM 2.5 and its chemical components is associated with an increased risk of asthma development in children. The heterogeneous nature of PM 2.5 should be considered in future health risk assessments., (Crown Copyright © 2021. Published by Elsevier Ltd. All rights reserved.)

Background: Studies have reported increasing incidence rates of paediatric diabetes, especially among those aged 0-5 years. Epidemiological evidence linking ambient air pollution to paediatric diabetes remains mixed., Objective: This study investigated the association between maternal and early-life exposures to common air pollutants (NO 2 , PM 2.5 , O 3 , and oxidant capacity [Ox; the redox-weighted average of O 3 and NO 2 ]) and the incidence of paediatric diabetes in children up to 6 years of age., Methods: All registered singleton births in Ontario, Ca nada occurring between April 1st , 2006 and March 31st , 2012 were included through linkage from health administrative data. Monthly exposures to NO 2 , PM 2.5 , O 3 , and O x were estimated across trimesters, the entire pregnancy period and during childhood. Random effects Cox proportional hazards models were used to assess the relationships with paediatric diabetes incidence while controlling for important covariates. We also modelled the shape of concentration-response (CR) relationships., Results: There were 1094 children out of a cohort of 754,698 diagnosed with diabetes before the age of six. O 3 exposures during the first trimester of pregnancy were associated with paediatric diabetes incidence (hazard ratio (HR) per interquartile (IQR) increase = 2.00, 95% CI: 1.04-3.86). The CR relationship between O 3 during the first trimester and paediatric diabetes incidence appeared to have a risk threshold, in which there was little-to-no risk below 25 ppb of O 3 , while above this level risk increased sigmoidally. No other associations were observed., Conclusion: O 3 exposures during a critical period of development were associated with an increased risk of paediatric diabetes incidence., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2020. Published by Elsevier Inc. All rights reserved.)

Pneumonia and influenza represent a significant public health burden in Canada and abroad. Knowledge of how this burden varies geographically provides clues to understanding the determinants of these illnesses, and insight into the effective management of health-care resources. We conducted a retrospective, population-based, ecological-level study to assess age- and gender-specific spatial patterns of pneumonia and influenza hospitalizations in the province of Ontario, Canada from 1992 to 2001. Results revealed marked variability in hospitalization rates by age, as well as clear and statistically significant patterns of high rates in northern rural counties and low rates in southern urban counties. A moderate yet significant level of positive spatial autocorrelation (Moran's I=0.21, P<0.05) was found in the global data, with significant, age-specific clusters of high values or 'hot spots' identified in several northern counties. Findings illustrate the need for geographically focused prevention strategies, and resource and service allocation policies informed by regional and population-specific demands.