Scientists predict climate change will bring more temperature spikes, which could be deadly to elderly people with chronic medical conditions.
Harvard University researcher Antonella Zanobetti's team combined temperature records with data from the U.S. Medicare program, which provides health insurance for Americans age 65 and older.
When summer temperatures got unusually hot, they found a higher risk of death among people who had been hospitalized for chronic medical conditions, "such as with diabetes or heart failure, chronic lung disease, or who survived a previous heart attack," Zanobetti says.
Over two decades, they found that death rates among these vulnerable, older men and women were higher in years when there were more extremes in summer temperatures. And even relatively small increases in extreme temperatures had a significant effect on death rates.
"For each one degree Celsius increase in summertime temperature variability, the death rate for elderly with chronic conditions increased between 2.8 percent to four percent, depending on the condition."
The biggest impact, that 4 percent increase, was on people with diabetes. People living in poverty and African Americans were also more likely to die when temperatures spiked. The risk was lower, however, for people living in cities with more green space.
Humans may be pretty good at adapting to different climates, but Zanobetti explains when you are elderly and suffering from a chronic disease, what scientists call thermoregulation may be more difficult.
"The problem is that, you know, while people tend to adapt to the usual temperature in their city, they might have more difficulties adapting to these temperature swings," she says.
The authors say this is the first study of its kind. If scientists' predictions of more temperature extremes turn out to be true, there may be a lot more research on this topic in the future.