The brief boost in risk usually doesn’t linger.
Artery-clogging atherosclerosis is a slow, silent process that often begins in one’s teens or 20s. Some people with atherosclerosis live out their lives completely untouched by it. Some develop chest pain (angina) or other problems when they exercise or are under stress. And some have heart attacks or strokes.
What kicks atherosclerosis over the edge, changing it from a relatively predictable, chronic problem to a potentially life-threatening emergency? Usually a trigger — a physical or emotional jolt that sparks a sudden change in the cardiovascular system.
Some triggers cause a surge in blood pressure. Some make the heart beat faster and harder. Others prompt blood to clot, constrict blood vessels, or cause bursts of inflammation. These can set in motion processes that culminate in the formation of a blood clot (leading to a heart attack or ischemic stroke), a tear in a blood vessel (leading to a hemorrhagic stroke), or a wild heart rhythm (leading to sudden cardiac arrest).
More than a dozen triggers have been identified so far. They range from shoveling snow and engaging in sexual activity to earthquakes and air pollution. How serious are they? A review by Harvard-affiliated researchers Murray A. Mittleman and Elizabeth Mostofsky takes the much-needed step of putting triggers into perspective (Circulation, July 19, 2011).
Known triggers for cardiovascular events
More than a dozen activities, events, and conditions can trigger heart attacks, strokes, and sudden cardiac arrests. We’ve listed them from highest absolute risk to lowest:
Relative and absolute
Most trigger studies give relative risks, which compare the risks between two groups. In one study, the risk of having a heart attack was 107 times higher among normally inactive individuals who did strenuous physical activity in the hour before the attack than among those who didn’t do strenuous activity.
What’s more important is the absolute risk. This is an individual’s chance of having a cardiovascular event over a particular period. Let’s take a normally inactive man whose chance of having a heart attack is moderately low. His absolute risk of having one in the hour after exercising is about 28 in a million — which doesn’t sound quite as frightening as a 107-fold increased relative risk.
Drs. Mittleman and Mostofsky used absolute risk to estimate the number of people who would need to perform a trigger or be exposed to one to cause a single extra heart attack. The numbers are reassuring. For instance, anger has a relative risk of about six, meaning that a person prone to episodes of anger is six times as likely to have a heart attack as someone who isn’t. In looking at absolute risk, though, the researchers determined that if 1,000 people at low risk of heart disease each had two episodes of anger a day, that would lead to one extra heart attack a year. Among a high-risk group, there would be five extra heart attacks.
The impact of triggers depends largely on cardiovascular health. They are far more likely to cause a heart attack, stroke, or cardiac arrest in a person with heart disease than in someone with a healthy heart and arteries. Physical condition also matters. Exercise or physical exertion is much more likely to trigger a heart attack in someone who leads a sedentary life than in someone who exercises regularly.
It’s almost impossible to avoid cardiovascular triggers, but you can reduce or inactivate their effects:
Lower your absolute risk. Keep your arteries in shape by exercising, not smoking, eating a heart-healthy diet, and controlling your blood pressure, cholesterol, blood sugar, and weight.
Blunt specific triggers. Regular exercise lessens the chance of having a heart attack while exercising, shoveling snow, or having sex. Manage stress, anger, or anxiety. Get vaccinated against pneumonia and get a yearly flu shot.
Avoid some triggers. If you’re out of shape, hire a teenager to shovel your walk. Wash your hands often, especially if you’ve been around someone with a cold or other respiratory infection. Walk away from confrontations. Try not to indulge in rich, high-calorie meals. Stay indoors during a heat wave or on days when air pollution is high.
This description of triggers is meant to empower you, not frighten you. Knowing the things that can set off a heart attack, stroke, or cardiac arrest can help you avoid them or lessen their power. Being aware of possible triggers can also help you respond faster if one does set off a heart attack or stroke. The quicker you act, the better off you’ll be.