Air pollution and overall mortality in the elderly

Relation

Q. Di, L. Dai, Y. Wang et al. Association of short-term air pollution exposure with mortality in older adults.JAMA. 2017;318(24):2446-2456.

Objective

To investigate whether particulate matter and ozone levels below current U.S. national air quality standards increase the risk of death in older adults.

Draft

To estimate a possible association, the study used a case-crossover design and conditional logistic regression using a 2-pollutant model with ozone in warm months (April to October each year) and short-term exposures to particulate matter (PM_2.5).

Participant

Study participants were all Medicare enrollees (generally over 65 and/or disabled), representing the entire U.S. Medicare population from 2000 to 2012. During the 13 years covered by the study, participants lived in nearly 40,000 zip code-specific communities. 22 million deaths were included in the regression dataset. Subgroups for non-whites, older than 85 years, Medicaid eligible, and 75 years and older were also correlated with contaminants.

Study parameters assessed

Daily exposures were assessed by zip code using estimates based on published and validated air pollution prediction models based on land use, chemical transport models, and satellite remote sensing data. This was useful for estimating daily exposures in rural areas that were not otherwise directly monitored. Ozone concentrations, PM_2.5Concentrations and death rates were examined to elucidate exposure-response relationships.

Key insights

There was a statistically significant association between increased mortality and the short-term increase of 10 μg/m³in PM_2.5(adjusted for ozone) and 10 ppb (parts per billion; 10⁻⁹) in ozone in the warm season (adjusted for PM_2.5) levels. With daily increases of 10 μg/m³in PM_2.5, there was a 1.05% increase in deaths. For 10 each⁻⁹Ozone deaths increased by 0.51%. Worryingly, there was no threshold for exposure to either compound considered safe.

Practice implications

Comment on this study in an interview withNew York TimesCo-author Joel D. Schwartz, a professor of epidemiology at Harvard, explained: “This means PM_2.5causing 20,000 additional deaths annually. Regardless, a 10 parts per billion reduction in ozone would save 10,000 lives per year.”¹

Although the Clean Air Act requires that the National Ambient Air Quality Standards (NAAQS) be evaluated every 5 years, very little was known about death rates relative to pollution levels prior to this studyunderthe NAAQS in vulnerable populations. This study shows the increased health risks associated with substandard PM levels_2.5and ozone pollution, suggesting the need to reevaluate the current NAAQS. The study is particularly impressive given the large cohort of older participants and the size of the geographical area covered, including previously unsurveilled rural regions.

This study shows the increased health risks associated with substandard PM levels_2.5and ozone pollution, suggesting the need to reevaluate the current NAAQS.

Information of this type would be useful to disseminate (similar to daily weather reports) to the general population, particularly in more densely populated, even slightly polluted areas. Because we know that air quality is associated with increased mortality, we need to educate our most vulnerable members of society, such as the elderly and those with cardiovascular disease, about the increased health risks of ozone and particulate matter.

Low-cost, personalized interventions such as face masks,²Air purifiers, antioxidant supplementation, and supportive lifestyle interventions to protect against cardiovascular events would be indicated³as many cardiac deaths are related to PM in the area_2.5-induced health effects. Heart attacks, strokes, heart failure, arrhythmias and cardiac death all increase when the concentration of particulate matter in the ambient air increases even briefly.⁴The mechanisms postulated for these effects include systemic inflammation, altered cardiac autonomic function, and an increase in atherosclerotic plaque formation. The effects were found to be additive in smokers versus non-smokers, most likely due to chronic pneumonia.⁶

Plant-based diet, exercise, stress management, and smoking cessation can help reverse cardiovascular atherosclerotic disease in as little as one year.^5.6

On the other side of the age continuum, a recent Chinese study of college students examined metabolic effects such as higher blood pressure, hormone levels, insulin resistance, and biomarkers of oxidative stress and inflammation in students exposed to higher PMs. The authors observed differences between treatments in glucose, amino acids, fatty acids and lipids. The biomarkers induced by PM_2.5They have been found to affect stress hormones: cortisol, cortisone, epinephrine and norepinephrine. These results may explain the mechanism behind the adverse health consequences. In particular, the use of air purifiers significantly reduced stress hormone levels.⁷