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Your Environment. Your Health.

Health Implications of Temperature Variability

Joel D. Schwartz, Ph.D.
Harvard School of Public Health
NIEHS Grant R21ES020695


Climate change is expected to bring increasing variability in summer temperatures, which could shorten life expectancy for older people with chronic medical conditions, according to a new NIEHS-funded study. Although other studies have looked at the short-term effects of heat waves, this study examined the long-term effects of climate change on life expectancy.


The researchers used Medicare data from 1985 to 2006 to follow the health of 3.7 million chronically ill people over age 65. They studied whether mortality related to variability in summer temperature in 125 cities and took into account other factors, such as winter temperature variance, ozone levels, and individual risk factors. They compiled results for 125 individual cities and then pooled the results.


Within each city, years with larger summer temperature swings showed higher death rates than years with smaller swings. Each 1 degree Celsius increase in summer temperature variability increased the death rate for elderly with chronic conditions between 2.8 and 4.0 percent, depending on the condition. In addition, the researchers found the mortality risk was 1 to 2 percent greater for African Americans and those living in poverty and for African Americans, while the risk was 1 to 2 percent lower for people living in cities with more green space.


Citation: Zanobetti A, O'Neill MS, Gronlund CJ, Schwartz JD. 2012 Summer temperature variability and long-term survival among elderly people with chronic disease. Proc Natl Acad Sci U S A 109(17):6608-6613.

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