Severe Cold Weather Sends Death Rate Soaring

Deaths linked to extreme cold account for 0.8 percent of the nation's annual death rate and outnumber those attributed to leukemia, murder and chronic liver disease combined, the study reports.

Cold-related deaths reduce the average life expectancy of Americans by at least a decade, it says.

The numbers are "remarkably large," said Enrico Moretti, a UC Berkeley associate professor of economics, and Oliver Deschenes, an associate professor of economics at UC Santa Barbara, in a December 2007 working paper, "Extreme Weather Events, Mortality and Migration."

Cities recording the biggest numbers of cold weather-related deaths include Chicago, Detroit, Minneapolis and Cleveland, according to Moretti and Deschenes.

They estimate that up to 3.2 percent of the annual deaths in those cities could be delayed if people reduced their exposure to extremely cold weather.

Ice and snow are beautiful but they can be deadly. (Photo credit unknown)

The study also says that population shifts from colder climates to warmer ones - for reasons such as better jobs, cheaper housing and sunshine - appear to delay an estimated 4,600 deaths a year.

The researchers also said that over the past 30 years, longevity gains associated with geographic mobility accounted for between four and seven percent of the increases in life expectancy in the United States.

In research conducted for the National Bureau of Economic Research, the economists looked at immediate and longer-term death rates after at least 24 hours at temperatures between 10 and 20 Fahrenheit degrees below normal for the county and the month observed.

Noting increasing concern that higher temperatures and incidence of extreme weather events caused by global warming could create major public health problems, the economists said they relied on actual, recorded data and avoided hypothetical possibilities.

They found that women account for two-thirds of deaths following a period of severe cold, although it is unclear why. Infants and men living in low-income areas also are at high risk of dying after a cold spell.

The death rate declines soon after scorching temperatures subside, while deaths after cold spells continue to increase for weeks, the economists found.

Death rates do not escalate after cold snaps that occur when the price of oil is high, the study shows.

Cardiovascular and respiratory diseases are the top causes of death for those who die following severe hot or cold weather.

Data for the extreme weather study came from the U.S. Multiple Causes of Death files and included the cause, date and age of death, the county where the death occurred in the continental United States, and the sex of the person who died.

The study found that those hardest hit by both heat and cold waves are adults 75 years of age or older, many of whom were already physically vulnerable and who would likely have died even in the absence of the temperature shocks.

The researchers acknowledged the geographic differences among the nation's 20 largest metropolitan statistical areas that were included in their study.

For example, residents of San Diego, Los Angeles, Fort Lauderdale and Phoenix recorded no bouts of extreme cold, while Philadelphians faced 31 cold days a year on average, New Yorkers 36, Bostonians 50, Chicagoans 57, Detroit residents 69, and Minneapolis residents 109.

Moretti and Deschenes said that evidence suggests that people can get acclimatized to the cold. The recorded death rate was substantially larger in countries where people were exposed to 10 or fewer cold days a year and lower in counties that have at least 90 cold days a year, they said.

Moretti said, there seem to be few immediate options for helping those most at risk deal with cold weather dangers: "A lifetime of deprivation is hard to counteract in the short run."

Their report is online at: http://www.econ.berkeley.edu/~moretti/weather_mortality.

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