Close up image of a caretaker helping older woman walk

Even small rises in summer temperatures may shorten life expectancy for seniors with chronic medical conditions, a new study reveals. 

Harvard University School of Public Health researchers studied Medicare data over almost 20 years to follow the long-term health of 3.7 million chronically ill people over 65. Study subjects lived in 135 U.S. cities.

Each 1° Celsius increase in summer temperatures increased the death rate for elderly with chronic conditions between 2.8% and 4.0%, depending on the condition, researchers said. The mortality risk increased the most for those with diabetes.

“People do not adapt as well to increased fluctuations around the usual temperature,” warned author and Harvard environmental epidemiologist Joel Schwartz, Ph.D. “That finding, combined with the increasing age of the population, the increasing prevalence of chronic conditions such as diabetes, and possible increases in temperature fluctuations due to climate change, means that this public health problem is likely to grow in importance in the future.”

The study will be published April 9 in the Proceedings of the National Academy of Sciences. U.S. Environmental Protection Agency and the National Institute of Environmental Health Sciences provided funding for the study.