Summer temperature variability may increase mortality risk for elderly with chronic disease: study

In recent years, scientists have predicted that climate change will not only increase overall world temperatures but will also increase summer temperature variability, particularly in mid- latitude regions such as the mid-Atlantic states of the U.S. and sections of countries such as France, Spain, and Italy. These more volatile temperature swings could pose a major public health problem, the authors note.

The researchers used Medicare data from 1985 to 2006 to follow the long-term health of 3.7 million chronically ill people over age 65 living in 135 U.S. cities. They evaluated whether mortality among these people was related to variability in summer temperature, allowing for other things that might influence the comparison, such as individual risk factors, winter temperature variance, and ozone levels. They compiled results for individual cities, then pooled the results, Xinhua reports.

They found that, within each city, years when the summer temperature swings were larger had higher death rates than years with smaller swings. Each one degree Celsius increase in summer temperature variability increased the death rate for elderly with chronic conditions between 2.8 percent and 4.0 percent, depending on the condition. Mortality risk increased 4.0 percent for those with diabetes; 3.8 percent for those who'd had a previous heart attack; 3.7 percent for those with chronic lung disease; and 2.8 percent for those with heart failure. Based on these increases in mortality risk, the researchers estimate that greater summer temperature variability in the U.S. could result in more than 10, 000 additional deaths per year.

In addition, the researchers found the mortality risk was one percent to two percent greater for those living in poverty and for African Americans. The risk was one percent to two percent lower for people living in cities with more green space.

Mortality risk was higher in hotter regions, the researchers found. Noting that physiological studies suggest that the elderly and those with chronic conditions have a harder time than others adjusting to extreme heat, they say it's likely these groups may also be less resilient than others to bigger-than-usual temperature swings.