May 23, 2017
Blizzard

How Weather Affects Your Health

by Berkeley Wellness  |  

Many people swear that their aches and pains are influenced by the weather, among them arthritis sufferers who look to their creaky joints as a dependable barometer. Migraine sufferers often blame their headaches on the weather, too, especially changes in weather. Some people believe that heart attacks are at least in part weather-related. And what about colds—are they more frequent in winter?

It’s hard to argue what people feel in their bones and hearts, literally and figuratively—but has science confirmed any solid connections? We take a look at the evidence.

Heart attacks

There may be a link between weather and heart attacks, at least in some people. A large study in northern France from more than 25 years ago found that sudden drops in barometric pressure, as before a bad storm, might bring on heart attacks in people at high risk. And a study from Croatia in 2014 found that a serious kind of heart arrhythmia (ventricular tachycardia) might also be linked to dropping barometric pressure, as well as increasing humidity (relative air moisture).

Other research points to links between cold weather and increases in blood pressure, blood viscosity, and workload on the heart, each of which can raise the risk of heart attack. Even a small drop in outdoor temperature might boost risk, according to a 2010 study in BMJ. A decrease of just 1.8°F on a single day translated into a 2 percent rise in the number heart attacks over the following 28 days.

Heart attack risk also increases in relation to snowfall, as a large Canadian study in CMAJ in February 2017 reported—presumably due, indirectly, to shoveling. It found a 16 percent increase in heart attack hospital admissions and a 34 percent increase in heart attack deaths the day after a snowfall of 8 inches in men (but not women), independent of age and cardiovascular risk factors. Similar correlations between snowfall and heart attacks have previously been reported in other northern locales. Shoveling is a “unique activity” that can particularly strain the heart, especially in combination with cold weather, the researchers noted.

But the relationship between cold weather and heart attacks is not so straightforward, with the incidence varying from area to area—cold wet weather seems to drive up the heart attack rate more noticeably in temperate climates than in colder places. For instance, in a 2014 study in PLOS ONE that involved people from 19 countries, cardiovascular deaths were higher in winter than in summer in certain places, such as Portugal and Japan—but no seasonal differences were seen in countries farther from the equator, such as Finland and Canada. You might think that northernmost countries with the coldest temperatures would have the highest mortality in winter, but the researchers hypothesized that people living in frigid climes are more prepared with warm clothing and homes that better protect them from the cold. Other possible explanations: Their bodies are better adapted to the cold, and physical activities may decline more in the coldest weather.

Summer can be a threat, too, notably for heart attack deaths. Hot weather—which taxes the heart so it has to work harder to keep the body cool—is a particular risk for poor people in U.S. cities, in large part because they are less likely to have air conditioning. Older people, who are less able to adapt physiologically to both hot and cold temperatures, and those who have diabetes, hypertension, or heart or lung disease, for example, are also at increased risk of dying from temperature extremes or from shifts in barometric pressure.

Aches and pains

Several studies have attempted to confirm (or debunk) whether pain is indeed triggered or exacerbated by cold, damp conditions, as so many people believe. In a 2014 study in BMC Musculoskeletal Disorders, 67 percent of 712 Europeans with osteoarthritis said that weather affected their joint pain. In a 2014 study in the journal Pain, people with hip osteoarthritis who completed questionnaires every three months for two years reported slight worsening of pain with increases in humidity, and slight worsening in function with increases in barometric pressure. And among some 135,000 male construction workers, those who worked in cold temperatures were more likely to report low back and neck pain than those working at higher temperatures, according to a 2013 study in the International Archives of Occupational and Environmental Health.

The Cloudy with a Chance of Pain project has gathered data from more than 13,000 participants in the U.K, who tracked their levels of chronic pain over a year using a smartphone app that automatically collected local weather data when they were logged in. Preliminary analyses showed an association between cloudy and rainy weather and increases in severe pain.

But in other studies, weather appears to have minimal, if any, effect, on pain. In 2016, a study in Pain Medicine of nearly 1,000 people in Australia found no relationship between acute low back pain and precipitation, humidity, and air pressure (though risk increased slightly with increased temperature). Moreover, arthritis pain in particular waxes and wanes, so while it’s tempting to link these ups and downs to changing weather, none of the studies prove causality. It’s possible, for example, that people exercise less in bad weather, and this lack of physical activity is what worsens symptoms. If you want to move from a cold, wet climate to a sunny dry one, you might be happier, but don’t count on that sunny dry climate to cure arthritis or other pain.

Headaches

People who get migraines often blame the weather, especially changes in weather. Though most research has not borne this out, a 2015 study in the Journal of Headache and Pain gives them some validity. Researchers in Taiwan looked at the headache diaries kept by 66 migraine patients over a year. Those who claimed to be affected by temperature changes had a significant increase in headaches during cold winter weather, unlike those who said they weren’t affected by temperature. Another study from Taiwan, in Cephalalgia in 2014, found that cluster headaches were more likely to occur during the transition from winter to spring, and from spring to summer.

Colds and flu

Viruses, not winter weather, are the cause of these infectious illnesses. Still, some preliminary studies suggest that physical stress from being cold can decrease resistance to viruses (by boosting stress hormones, for instance, and reducing antibodies in saliva) or that breathing in cold air or heated air that’s not adequately humidified increases susceptibility by drying the nasal passages and airways and constricting blood vessels in them.

This idea was supported by a large 2015 study in Viruses, which found that drops in temperature and humidity preceded onset of rhinovirus infections (colds) by several days in people who sought medical attention for respiratory symptoms. And a much-publicized though somewhat flawed study more than a decade ago, from the Common Cold Centre at Cardiff University, found that people who sat in their underwear with their bare feet in icy water for 20 minutes were more likely than a control group to report having symptoms of colds during the next five days.

It makes sense to keep warm and dry in cold weather, but if you get wet and chilled, that doesn’t mean you’re doomed to start sneezing. One thing is clear: You “catch cold” from sick people, not from the weather. And the main reason why colds increase in winter is that people spend more time indoors in close enough proximity to swap germs. Being in cold, damp weather may increase the risk slightly (if at all). If you lived in total isolation in a cold, damp climate and were not exposed to cold viruses from other people, you’d never catch a cold, no matter how chilled you got.

Mood

Many people believe that weather affects their mood and mental state. In a small 2016 study in the Journal of Affective Disorders, university students receiving mental health counseling had greater mental distress when there was a seasonal reduction in the amount of sunshine, and reductions in stress with increased sunshine. This is not surprising since humans, like most animals, are affected by sunlight or the lack of it, both physically and emotionally—some more than others. Seasonal Affective Disorder (SAD) is recognized as a type of clinical depression that occurs during the shorter, darker days of late autumn and winter, especially in more northern regions. It can be likened to the general winter malaise and lethargy that many of us experience, but is more severe and debilitating.

Bottom line

Weather is a powerful force undeniably linked to human health and well-being. Hot climates can cause heat stroke and encourage the breeding of disease-carrying mosquitoes and the multiplication of harmful microbes. Cold weather can cause hypothermia and frostbite. Hurricanes and blizzards can destroy cities, or at least shut them down. Droughts can cause food shortages. And there’s good evidence for seasonal variations in mood in some people. But weather is not usually directly to blame for headaches, joint pain, colds, or even most heart attacks—though evidence is accumulating that it may sometimes play a role.

Also see Travel Safely in Hot Weather.