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The
Killer Season
But not so fast: Demographically
speaking, cold is actually a far bigger killer than heat. In the Northern
Hemisphere, the Grim Reaper makes more house calls in December, January,
and February, while—this year's statistically anomalous summertime
mortality excepted—he tends to take time off during July, August, and
September (naturally, this is reversed in the Southern Hemisphere). One
study calculated that in the United Kingdom in the 1990s, more than 80,000
people died of cold-related causes per year—or more than 100 times the
figure for heat-related deaths. All bets are off in the developing world,
where the hottest months (whichever part of the calendar they fall on) are
more deadly. Some of the demographers' kernels
of insight on the seasonality of mortality hold up across climates,
cultures, and time zones: For example, the cold can kill you—and in some
climates and conditions, national death rates are as much as 30 percent
higher in the winter. Although cancer (No. 2 on the list of leading causes
of death in the United States) knows no season, the body's reaction to
cold—particularly among elderly men, who are most susceptible to
climatic change—can increase the chances of blood clotting, which in
turn leads to a higher incidence of death from heart attacks and strokes
(Nos. 1 and 3 on the hit list). Similarly, the cold facilitates the
transmission of respiratory diseases (No. 4) and ensures that they're more
severe than strains contracted at other times of the year. And winter
sometimes gives a final push to people who were already ill and vulnerable
and likely to die soon anyway (this is impolitely called
"harvesting" in the academic literature). On the surface, then, logic
suggests that the colder the climate, the greater the number of wintertime
"excess deaths"—that is, the difference between mortality in
the winter and the average expected number of deaths in the summer. Or
not: In what Roland Rau at the Max Planck Institute for Demographic
Research terms the "seasonality paradox," levels of cold-weather
excess deaths in populations in relatively mild climates, such as Ireland
or Portugal, are actually higher than in populations in truly
eyeball-freezing climes like Canada, Russia, and Scandinavia. Generally
speaking, people who are used to the cold know how to take care of
themselves when the mercury drops. That said, the fruits of economic
prosperity—such as more people using toasty warm private cars instead of
drafty public transportation and being able to afford heat for their
houses—are gradually reducing the levels of wintertime excess deaths in
relatively mild climates. One study of Yakutsk—one of the
most bitterly chilly cities in eastern Siberia, and thus the world, where
the average temperatures between October and March sink to a
positively unbalmy minus 16 degrees Fahrenheit—concluded that lower
temperatures did not cause any significant increase in mortality. The
frosty denizens of Yakutsk exercised the seemingly obvious safety measures
of wearing layers (more than four, on average), staying where it's warm,
and keeping the heat cranked up. A small increase in mortality stemming
from respiratory disease due to breathing cold air was offset by a
decrease in death from accidents—presumably because during chilly spells
cold enough to freeze bone marrow, few people go anywhere or do much at
all, significantly reducing the opportunities for accidents. (Falling
icicles, which each winter skewer roughly 100 Russians who happen to be
under the wrong building eave at the wrong time, haven't—yet—been the
subject of extensive demographic research.) The dynamics of the seasonality
of death change for folks at the more youthful end of the population
spectrum, as not many young people die from cold-inspired heart attacks.
Mortality among the young is relatively higher in the summertime, in part
because their key killers—motor vehicle accidents, poisoning, drowning,
and other unintentional injuries, as well as suicide, homicide, and other
external causes—generally tend to strike more when it's warm. In Russia,
summertime mortality soars for the demographic groups prone to combine
imbibing copious amounts of alcohol with a dip in the local swimming hole;
seasonal diving teams make a sport of dredging for the bodies of the
drowned after every weekend. Mortality among the sober, but unsupervised,
children of drunk-drowners also escalates. This notwithstanding, overall,
excess deaths of young people in the summertime are far outnumbered by
those of the elderly in the wintertime. The cold-equals-death equation is
turned on its head for much of the developing world, where
gastrointestinal problems (such as diarrhea, gastroenteritis, and
dysentery) that flourish during the summer account for a significant
portion of all deaths. Also, in much of the developing world, winter-month
temperatures remain semi-tropical, making it difficult to die of
cold-related causes. Furthermore, many of the rich persons' diseases that
fell the elderly in the developed world, with a bit of help from the
cold—like strokes and heart disease—figure less prominently on the
list of the leading causes of mortality in the Third World. Not everything bad happens during
the chillier times of year, though: One study found that among people
older than 50 years of age in Austria and Denmark, those born in the
autumn months (and, best of all, November) have a slightly higher life
expectancy than those born in the spring (or, worst of all, May). The
mothers of fall babies enjoyed better nutrition during the summer months,
immediately prior to giving birth, while spring-baby mothers had a
comparatively poor diet—which in turn affected the long-term health of
their offspring. One of the few silver linings of
the seasonality of mortality is the impact of global warming on wintertime
deaths. One study suggests that an increase in temperature of roughly 3.6
degrees Fahrenheit by the middle of this century would
boost total heat-related deaths in the United Kingdom more than threefold,
to just under 3,000, but the number of cold-related deaths would drop by
25 percent, or 20,000, to 60,000. In the meantime, keep that coat zipped. Thanks to Roland Rau at the Max
Planck Institute for Demographic Research, Craig Feinstein at the U.S.
Social Security Administration, William R. Keatinge of Queen Mary and
Westfield College of the University of London, and Martin McKee of the
European Centre on Health of Societies in Transition at the London School
of Hygiene and Tropical Medicine, University of London Copyright
© 2002 Global Action on Aging |
