Temperature Variability May Increase Mortality Risk

Photo: Thermometer 

New research from Harvard School of Public Health (HSPH) suggests that seemingly small changes in summer temperature swings — as little as 1 degree Celsius more than usual — may shorten life expectancy for elderly people with chronic medical conditions, and could result in thousands of additional deaths each year.

While previous studies have focused on the short-term effects of heat waves, this is the first study to examine the longer-term effects of climate change on life expectancy. "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," said Antonella Zanobetti of HSPH. "This variability can be harmful for susceptible people."

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 United States 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 found that, within each city, years when the summer temperature swings were larger had 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 per cent and 4.0 per cent, depending on the condition. Mortality risk increased 4.0 per cent for those with diabetes. 3.8 per cent for those who'd had a previous heart attack. 3.7 per cent for those with chronic lung disease and 2.8 per cent 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.

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 is likely these groups may also be less resilient than others to bigger-than-usual temperature swings.; Source: Harvard School of Public Health

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