INCREASED fluctuations in summer temperatures caused by climate change could lead to tens of thousands of extra deaths among elderly people each year, a study has warned.
Scientists examined the impact on mortality of day-to-day variations in temperature during the summer, which are expected to increase as a consequence of climate change. They found that even small temperature swings, of as little as 1C more than usual, may shorten the life expectancy of elderly people with chronic medical conditions.
Previous studies have focused on the short-term effects of heat waves but this is the first study to examine the longer-term effects of climate change on life expectancy.
In recent years, scientists have predicted that climate change will not only increase overall world temperatures but will also increase summer temperature variability.
The authors looked at the impact of temperature variations on elderly people with diabetes, heart failure, chronic lung disease and those who have survived a previous heart attack.
Antonella Zanobetti, senior research scientist in the Department of Environmental Health at Harvard School of Public Health, who led the study, said: “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.
“This variability can be harmful for susceptible people.”
The researchers used data from 1985 to 2006 to follow the long-term health of 3.7 million chronically ill people over the age of 65 and living in 135 US cities.
They found that years when the summer temperature swings were larger had higher death rates than years with smaller swings.
Each 1C increase in summer temperature variability raised the death rate for elderly people with chronic conditions between 2.8 per cent and 4 per cent, depending on the condition.
Mortality risk increased 4 per cent for those with diabetes, 3.8 per cent for those who had 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 US alone could result in more than 10,000 additional deaths per year.
The study is published in the Proceedings of the National Academy of Sciences.