Even small swings in temperatures could put elderly people with chronic illnesses such as diabetes, heart failure and lung disease at greater risk of death throughout summer, a new study indicates.
Researchers from the Harvard School of Public Health in Boston found temperature fluctuations related to climate change could claim thousands of lives every year.
Experts predict climate change could increase variations in summer temperatures, particularly in the mid-Atlantic states and in parts of France, Spain and Italy. In these more volatile regions, this could pose a serious public health risk, the study authors claimed.
"The effect of temperature patterns on long-term mortality has not been clear to this point. We found that, independent of heat waves, high day-to-day variability in summer temperatures shortens life expectancy," study author Antonella Zanobetti, a senior research scientist in the department of environmental health at Harvard, said. "This variability can be harmful for susceptible people."
How the study was done
Using Medicare data from 1985 to 2006, the researchers tracked the long-term health of 3.7 million chronically ill people older than 65 living in 135 American cities. After considering each person's individual risk factors, they determined if any of these people died due to variability in summer temperature.
The study, published in the Proceedings of the National Academy of Sciences, revealed that years with larger summer temperature swings had higher death rates than those with smaller swings. This was true for each city examined.
The researchers also noted each one-degree Centigrade increase in summer temperature variability increased the death rate for elderly with chronic conditions by between 2.8% and 4%.
More specifically, the mortality risk for those with diabetes increased 4%. It also rose 3.8% for people who had suffered a previous heart attack, 3.7% for those with chronic lung disease and 2.8 % for people with heart failure.
The temperature-related death risk was 1% to 2% higher for black people as well as those living in poverty, the study noted. The risk of death was also higher for the elderly people living in hotter areas.
Based on these findings, the researchers estimated that greater summer temperature variability in the United States could result in more than 10,000 additional deaths every year.
"People adapt to the usual temperature in their city. That is why we don't expect higher mortality rates in Miami than in Minneapolis, despite the higher temperatures," study senior author Joel Schwartz, a professor of environmental epidemiology at Harvard, explained.
"But people do not adapt as well to increased fluctuations around the usual temperature. 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," Schwartz added.
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