Winter's a wonderland, but dangerous, too.

Content provided by the Faculty of the Harvard Medical School

Winter's a wonderland, but dangerous, too.

Mortality rates go up during the winter months. To stay healthy, stay warm and vaccinated — and install carbon monoxide detectors.

April may be a cruel month with its mix of memory and desire, but winter — it’s the deadliest of seasons. In most northern countries and in some of southern Europe, death rates peak this time of year. Heart attacks and other serious cardiac problems are more common in winter. There’s flu to contend with, too. Researchers tend to blame cold weather — yes, it really is bad to get a chill — and poor housing. But long nights and vitamin shortfalls may be a factor, too. The best advice is the same old: Dress warmly. Or get to a nice, warm beach sometime this month or next — wearing sunscreen, of course.

Here’s a rundown of some winter-related dangers:

Heart attacks and other heart problems

In temperate climates, there’s a fairly consistent pattern of increased deaths and hospitalizations for heart disease and stroke during the winter. In some years and in some countries, the winter-summer difference may be as great as 70%.

Cold weather is the most likely cause. Blood pressure increases when you get cold because your blood vessels constrict to retain body heat. Higher blood pressure puts more strain on the heart, and eventually may damage the lining of blood vessels, but an interesting French study last year found that only people who already had high blood pressure were susceptible to cold weather–related heart attacks, presumably because their blood pressure was more easily pushed to dangerous levels. Chilly temperatures also affect the blood itself, increasing fibrinogen levels and the concentration of some other clotting factors.

But Canadian researchers found that the death rate from congestive heart failure in France and Quebec are the same, even though Quebec gets much colder. Britain has milder winters than the Scandinavian countries but worse wintertime heart disease statistics. And the typical seasonal pattern of a winter peak and summer trough in heart attack deaths has been found in Los Angeles County, where what passes for winter resembles spring in other places. So maybe cold isn’t the only reason for the seasonal variations.

A cluster of brain cells called the suprachiasmatic nucleus regulates the secretion of hormones such as cortisol, melatonin, and vasopressin — all of which can affect the heart. Those cells also process signals from the optic nerve. So, according to one theory, the short days and long nights of winter threaten the heart because a light-deprived part of the brain throws hormone levels out of whack.

Another explanation for winter’s increase in heart-related troubles is our holiday eating, drinking, and general carrying on. Some studies show the winter spike in heart attacks strikes near the holidays.

So what should you do? Even if there are other factors at work, it’s pretty clear that cold weather is one. So bundle up, and keep your house and car nice and toasty. As for those short days, bright lights help with happiness during the winter (see seasonal affective disorder on the next page). Maybe they keep hearts healthier, too.

Flu

Winter is the peak season for flu. In colder climes, the respiratory viruses spread more easily because people are inside and in closer contact. But flu experts think that there may be something about winter — cooler air, less daylight — that spurs the viruses to replicate after lying dormant in animals during the off-season.

Flu infections are blamed for about 36,000 deaths in the United States every year. There’s some evidence that flu is also partly responsible for the winter surge in heart attacks and stroke. A flu infection can increase blood pressure, stir up white blood cell activity, and change C-reactive protein and fibrinogen levels in the blood. All are bad news for your heart. Several studies have shown that flu shots seem to cut heart attack and stroke risk in half.

That impressive statistic may not be very reassuring when the flu vaccine is in short supply because of manufacturing problems. But in 2005, an estimated 58 million doses were available at the beginning of the winter, so it’s by no means hopeless. Ask your doctor about getting a flu shot. January’s not too late. And according to federal guidelines, anyone 65 or older and people with a chronic disease are among those who should get vaccinated, notwithstanding the shortage. An alternative to the flu shot is the nasal vaccine, FluMist. It contains three live, but weakened, flu viruses. The viruses are temperature sensitive so they grow in the nose and throat, stimulating an immune response, but not in the lower respiratory tract, where the temperature is higher. FluMist is approved for use in people from ages 5 to 49.

Snow shoveling

Every year northern emergency rooms fill up with people who are having heart attacks or who broke a bone while shoveling snow. Arm exercise, especially when you are upright and lifting, puts a terrific strain on your heart. In controlled experiments, just two minutes of heaving snow speeds up the heart so it’s beating above the upper limit recommended for safe aerobic exercise (85% of its maximum speed). Study after study shows a sudden increase in cardiovascular mortality after blizzards, especially if the white stuff is heavy and wet. Particularly if you’re out of shape, safe snow shoveling may mean no snow shoveling. Buying a snow blower is one obvious solution. If you must shovel, push rather than lift the snow as much as possible. And take your time.

Seasonal affective disorder

Winter puts many people in a gloomy state of mind. But for about 1%–2% of Americans, the winter blues-cum-blahs are worse than that. They tumble into full-fledged, clinical depression. In the 1980s, psychiatrists named the condition seasonal affective disorder (SAD). According to one popular theory, people are afflicted with it because their light-sensitive biological clocks don’t adjust to winter darkness. There may also be a cultural ingredient: SAD is relatively uncommon in Iceland and northern Russia, which certainly have plenty of long winter nights.

Exposure to bright light helps lift the mood of people with SAD, and special light-therapy lamps are available. But don’t underestimate the power of just getting outside. One study found that walking for an hour in sunlight was as effective as 21/2 hours of artificial light.

Interestingly, suicides peak in the spring and summer, not the winter. Emile Durkheim, the 19th century French sociologist, wrote about the pattern over a century ago. Some research has found that the suicide seasonality is waning. Experts say the change might be caused by increased personal communication year-round because of phones and computers and more effective treatment of depression.

Vitamin D

Vitamin D is generated by sunlight hitting the skin, so levels of the “sunshine” vitamin dip in the winter among people living in the northern latitudes. The vitamin’s main role is to keep bones healthy by signaling your intestines to absorb more calcium into the bloodstream. But vitamin D also plays a cardiovascular role, influencing the renin-angiotensin system that affects blood pressure. It also helps maintain the health of heart and blood cells. Several epidemiological studies have found that people with high vitamin D levels have low rates of heart attack and heart failure.

The evidence for heart protection is still iffy, but if you’re a northerner, you should keep up your vitamin D intake anyway for the sake of your bones. Most multivitamins have 400 IU. The best food sources are fatty fish like salmon and mackerel, fortified dairy products, and breakfast cereals (check those labels).

Hypothermia

About 600 Americans die each winter from hypothermia — a core body temperature below 95° F. When the body gets that cold, the heart beats irregularly and the kidneys start to fail. Brain function also starts to deteriorate, so you can’t think clearly and may not realize the danger you’re in. Older people are especially susceptible because with age, the body doesn’t adjust as well to cold weather. Cases may occur even in relatively mild weather. Wet clothing is a common cause because it wicks away body heat instead of holding it in. Alcohol is frequently involved, too. Besides impairing judgment, alcohol opens up (dilates) blood vessels beneath the skin, which creates a misleading sensation of warmth even as body heat escapes. Anyone with hypothermia needs immediate medical attention. You should remove any wet clothing and warm the center of the body — the chest, head, neck, and groin. If the person is conscious and alert, then tea, coffee, and most other warm liquids will help, but alcohol won’t — despite all those images of brandy-bearing St. Bernards.

Frostbite

When your body gets chilled, it reacts by constricting blood vessels near the skin to prevent heat loss. Your hands, feet, ears, and nose may pay dearly for this energy conservation because it makes them more vulnerable to frostbite.

Frostnip is when the skin becomes red and swollen, but never completely numb. It hurts, but if you gradually warm up, there’s no lasting damage. With frostbite, ice crystals may form in and between cells. Some cells die from it. Low blood flow may kill others.

Mild cases of frostbite can be treated with rewarming, which may hurt. Start with cool or lukewarm water. If the affected area is large or the freezing seems to have penetrated muscles and tendons, then expert medical attention is needed.

Carbon monoxide poisoning

Carbon monoxide (CO) is a colorless and odorless but highly toxic gas produced by the combustion of kerosene, natural gas, oil, wood, and pretty much anything else. We’re in greater danger from CO in winter because that’s when we’re most likely to be burning for heat in enclosed spaces. About 500 Americans die from unintentional carbon monoxide poisoning each year. Many more may feel sick during the winter because of low-level exposure they may not be aware of.

Probably the most important preventive measure is keeping your furnace well maintained so that the fumes are properly vented outdoors. You can also purchase a carbon monoxide detector for under $40.

Of course, for anyone living in temperate climes, the winter months will always be hard. That’s just the way it is. Some say it builds character. If you can’t flee southward, nothing we suggest can change that wintry truth. Still, by taking a few basic — and fairly simple — steps, you can go a long way to ensuring that you avoid the worst of winter’s woes.

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Last updated:	August 21, 2006