April 18, 2012

Will D.C.'s Summers Kill Me?


According to Harvard School of Public Health researchers, I'm more at risk from swings in summer temperatures than I am from the brutal, relentless heat and humidity of Washington summertimes.

The new research suggests that even small variations in average summer temperatures -- increases as small as one degree centigrade above "normal" -- may shorten life expectancy for elderly people with chronic medical conditions, and could result in thousands of additional deaths every 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 temporary patterns on long-term mortality has not been clear up to this point. We found that, independent of heat waves, high day to day variability in summer temperatures shortens life expectancy," said Antonella Zanobetti, the lead author of the study. "This variability can be harmful for susceptible people."

In recent years, scientists have predicted that climate change will not only increase world temperatures generally but will also increase summer temperature variability, particularly in mid-latitude regions like the mid-Atlantic states of the U.S. (that's DC!) and sections of other countries, including France,Spain, and Italy.

Previous studies have confirmed the connection between heat waves and higher death rates. But this new research goes a step further. Although heat waves can kill in the short term, the authors say, even minor temperature variations caused by climate change may also increase death rates over time among elderly people with diabetes, heart failure, chronic lung disease, or those who have survived a previous heart attack.

Well-Designed Study
The researchers used Medicare data from 1985 to 2006 to follow the long-term health of 3.7 million chronically ill people over the age of 65 living in 135 U.S. cities. Study leaders evaluated whether mortality among their subjects was related to variability in summer temperatures, allowing for other things that might influence the comparison, like individual risk factors, winter temperature variance, and ozone levels.

They found that, within each city, years when the summer temperature swings were larger produced higher death rates than years with smaller swings. Every one degree centigrade increase in summer temperature variability increased the death rate for elderly with chronic conditions between 2.8% and 4.0%, depending on the condition. Mortality risks were higher for those with diabetes, chronic lung disease, heart failure, and  those who'd had a prior heart attack.

Based on these increases in mortality risks, the researchers estimate that greater summer temperature variability in the U.S. could result in more than 10,000 additional deaths per year                                                                                                                                                                                                                   
They also found that the mortality risks were greater for those living in poverty and for African-Americans.

Good and Bad News for DC
The mortality risk was 1 to 2 % lower for people living in cities with more green space. Three cheers for Washington's abundance of trees and parks!

Mortality risk was higher in hotter regions, the researchers found. Noting that psychological 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 be less resilient than others to bigger-than-usual temperature swings.

My hopes for survival in this city-on-a-swamp were boosted by the finding that the impact of temperature fluctuations was blunted in cities where air conditioning was common, and by this quote:
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.
 Those hopes were then dashed by this quote:
But people do not adapt as well to increased fluctuations around the usual temperature.
Yesterday we hit a high of 90 in Washington. Today it's a comfortable 73. The forecast for tomorrow: 59.

Oh well. I've lived a rich, full life... and I love this city.

Seriously, however, this report portends a growing health problem, given the ever-growing number of seniors, the increase of chronic conditions like diabetes, and the possible increase in temperature fluctuations due to climate change.
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