Air Pollution and the Effectiveness of Positive Airway Pressure Therapy in Individuals With Sleep Apnea: A Retrospective Community-Based Repeated-Measures Longitudinal Study.

BACKGROUND: Ambient air pollution may affect the severity of untreated OSA, but it is unknown whether air pollution adversely impacts the effectiveness of positive airway pressure (PAP) therapy. RESEARCH QUESTION: Do short-term changes in outdoor air pollution adversely impact adults with OSA using PAP therapy? STUDY DESIGN AND METHODS: We conducted a retrospective community-based repeated-measures longitudinal study of adults with OSA who purchased a PAP device from a registered equipment provider between 2013 and 2017 (Ontario, Canada) and had data on the daily device-derived residual apnea-hypopnea index (AHIFlow). We linked daily PAP-derived data to air pollution databases using postal codes. The primary exposures were mean nocturnal (8 pm to 8 am) residential concentrations of ozone, fine particulate matter, nitrogen dioxide, carbon monoxide, sulfur dioxide, and the Air Quality Health Index (AQHI). Potential confounders considered were demographics, season and year of exposure, initial OSA severity, other PAP parameters, and climate-related variables. RESULTS: Eight thousand one hundred forty-eight adults were analyzed with a median of 89 days (interquartile range [IQR], 29-302 days) of observation during which PAP was used for ≥ 4 h. The median daily AHIFlow was 1.2/h (IQR, 0.5-2.5/h). In mixed multivariate regression analyses, an increase in air pollution was associated with a statistically significant increase in AHIFlow for most statistical models. The largest effect was for the AQHI: an increase in AHIFlow while comparing highest vs lowest quartiles was 0.07/h (95% CI, 0.05-0.10/h). INTERPRETATION: We demonstrated a modest but statistically significant increase in residual respiratory events during PAP therapy associated with an increase in air pollution concentrations.

Associations between air pollution and cardio-respiratory physiological measures in older adults exercising outdoors.

We examined whether exercising indoors vs. outdoors reduced the cardio-respiratory effects of outdoor air pollution. Adults ≥55 were randomly assigned to exercise indoors when the Air Quality Health Index was ≥5 and outdoors on other days (intervention group, n = 37), or outdoors everyday (control group, n = 35). Both groups completed cardio-respiratory measurements before and after exercise for up to 10 weeks. Data were analyzed using linear mixed effect regression models. In the control group, an interquartile range increase in fine particulate matter (PM2.5) was associated with increases of 1.4% in heart rate (standard error (SE) = 0.7%) and 5.6% (SE = 2.6%) in malondialdehyde, and decreases of 5.6% (SE = 2.5%) to 16.5% (SE = 7.5%) in heart rate variability measures. While the hypothesized benefit of indoor vs. outdoor exercise could not be demonstrated due to an insufficient number of intervention days (n = 2), the study provides evidence of short-term effects of air pollution in older adults. ISRCTN #26552763.

The Oakville Oil Refinery Closure and Its Influence on Local Hospitalizations: A Natural Experiment on Sulfur Dioxide.

Background: An oil refinery in Oakville, Canada, closed over 2004⁻2005, providing an opportunity for a natural experiment to examine the effects on oil refinery-related air pollution and residents' health. Methods: Environmental and health data were collected for the 16 years around the refinery closure. Toronto (2.5 million persons) and the Greater Toronto Area (GTA, 6.3 million persons) were used as control and reference populations, respectively, for Oakville (160,000 persons). We compared sulfur dioxide and age- and season-standardized hospitalizations, considering potential factors such as changes in demographics, socio-economics, drug prescriptions, and environmental variables. Results: The closure of the refinery eliminated 6000 tons/year of SO2 emissions, with an observed reduction of 20% in wind direction-adjusted ambient concentrations in Oakville. After accounting for trends, a decrease in cold-season peak-centered respiratory hospitalizations was observed for Oakville (reduction of 2.2 cases/1000 persons per year, p = 0.0006 ) but not in Toronto (p = 0.856) and the GTA (p = 0.334). The reduction of respiratory hospitalizations in Oakville post closure appeared to have no observed link to known confounders or effect modifiers. Conclusion: The refinery closure allowed an assessment of the change in community health. This natural experiment provides evidence that a reduction in emissions was associated with improvements in population health. This study design addresses the impact of a removed source of air pollution.

Air Health Trend Indicator: Association between Short-Term Exposure to Ground Ozone and Circulatory Hospitalizations in Canada for 17 Years, 1996⁻2012.

The Air Health Trend Indicator is designed to estimate the public health risk related to short-term exposure to air pollution and to detect trends in the annual health risks. Daily ozone, circulatory hospitalizations and weather data for 24 cities (about 54% of Canadians) for 17 years (1996⁻2012) were used. This study examined three circulatory causes: ischemic heart disease (IHD, 40% of cases), other heart disease (OHD, 31%) and cerebrovascular disease (CEV, 14%). A Bayesian hierarchical model using a 7-year estimator was employed to find trends in the annual national associations by season, lag of effect, sex and age group (≤65 vs. >65). Warm season 1-day lagged ozone returned higher national risk per 10 ppb: 0.4% (95% credible interval, -0.3⁻1.1%) for IHD, 0.4% (-0.2⁻1.0%) for OHD, and 0.2% (-0.8⁻1.2%) for CEV. Overall mixed trends in annual associations were observed for IHD and CEV, but a decreasing trend for OHD. While little age effect was identified, some sex-specific difference was detected, with males seemingly more vulnerable to ozone for CEV, although this finding needs further investigation. The study findings could reduce a knowledge gap by identifying trends in risk over time as well as sub-populations susceptible to ozone by age and sex.

Cardiorespiratory Effects of Air Pollution in a Panel Study of Winter Outdoor Physical Activity in Older Adults.

OBJECTIVE: The aim of this study was to assess cardiorespiratory effects of air pollution in older adults exercising outdoors in winter. METHODS: Adults 55 years of age and older completed daily measurements of blood pressure, peak expiratory flow and oximetry, and weekly measurements of heart rate variability, endothelial function, spirometry, fraction of exhaled nitric oxide and urinary oxidative stress markers, before and after outdoor exercise, for 10 weeks. Data were analyzed using linear mixed effect models. RESULTS: Pooled estimates combining 2014 (n = 36 participants) and 2015 (n = 34) indicated that an interquartile increase in the Air Quality Health Index was associated with a significant (P < 0.05) increase in heart rate (0.33%) and significant decreases in forced expiratory volume (0.30%), and systolic (0.28%) and diastolic blood pressure (0.39%). CONCLUSION: Acute subclinical effects of air pollution were observed in older adults exercising outdoors in winter.

Cardio-Respiratory Effects of Air Pollution in a Panel Study of Outdoor Physical Activity and Health in Rural Older Adults.

OBJECTIVE: To examine cardio-respiratory effects of air pollution in rural older adults exercising outdoors. METHODS: Adults 55 and over completed measurements of blood pressure, peak expiratory flow and oximetry daily, and of heart rate variability, endothelial function, spirometry, fraction of exhaled nitric oxide and urinary oxidative stress markers weekly, before and after outdoor exercise, for 10 weeks. Data were analyzed using linear mixed effect models. RESULTS: Pooled estimates combining 2013 (n = 36 participants) and 2014 (n = 41) indicated that an interquartile increase in the air quality health index (AQHI) was associated with a significant (P < 0.05) increase in heart rate (2.1%) and significant decreases in high frequency power (-19.1%), root mean square of successive differences (-9.5%), and reactive hyperemia index (-6.5%). CONCLUSIONS: We observed acute subclinical adverse effects of air pollution in rural older adults exercising outdoors.