Physical Work May Raise Heart, Stroke Risk

Exercise is known to reduce the risk of heart disease. But a physically demanding job may increase risk, two new studies suggest. One study looked at 500 adults who had a first stroke, heart attack or other heart-related event. They were more likely to have physically demanding jobs than a comparison group of 500 healthy adults. This was true even after researchers adjusted the numbers for age, smoking and other factors that affect heart attack and stroke risk. A second study included 14,000 middle-aged men who did not have heart disease. But those with physically demanding jobs were more likely to develop it during 3 years of follow-up. And that risk increased almost 5-fold if they also exercised during their leisure time. For people with less active jobs, on the other hand, heart disease risk dropped 60% if they exercised during leisure time. Some of these results surprised researchers. They said the higher risk for those with physically active jobs may be related to stress or less access to health care. Both studies were presented at a conference. HealthDay News wrote about them April 18.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

The advice to get regular exercise is nearly universal. And that makes sense. Study after study has shown health benefits related to exercise. The list is getting longer all the time. Exercise may reduce your risk of:

• Heart and blood vessel disease (including heart attack and stroke)
• Certain types of cancer
• Osteoporosis
• Depression
• Alzheimer's disease

So if you're physically active at your job, your risk of stroke and heart disease should be lower, right? Not so fast. Two new studies suggest that just the opposite may be true.

The first study looked at people who had a heart attack, stroke or other heart-related event. They were compared with otherwise similar people who did not have these problems. The researchers found that:

• Those who had problems were more likely to work at a job that was physically demanding than those who were healthy.
• The less physically demanding the job, the lower the risk of heart disease or stroke.
• The results were confirmed even after accounting for factors known to increase the risk of heart and blood vessel disease. These factors include smoking, high blood pressure, family history, high cholesterol and diabetes.
• The results held up even after accounting for whether a person maintained a Mediterranean diet. This diet includes mostly fruits, vegetables, whole grains, legumes, fish, nuts, olive oil and wine (in moderation). It has been linked with a reduced risk of heart disease.

The second study looked at physical demands on the job and also the effect of leisure-time exercise. More than 14,000 middle-aged men who did not have heart disease filled out questionnaires about both kinds of activities. Researchers kept track of people for more than 3 years. After accounting for standard risk factors, they found that:

• As with the first study, heart and blood vessel disease was more common among men with physically demanding jobs.
• Among men with less active jobs, moderate- to high-intensity leisure-time exercise was linked with a 60% lower risk.
• Leisure-time exercise did not have this protective effect for men whose jobs were physically demanding. In fact, it appeared to increase their risk by nearly 5 times.

These results surprised me. How can regular exercise reduce your risk of heart disease while a physically demanding job increases risk? There are several possibilities:

• Physically demanding jobs may come with psychological stress that could increase risk.
• Perhaps "physical activity" at work is quite different from that during leisure-time exercise. Lifting boxes into a truck every few minutes might not provide the same benefits as sustained aerobic exercise from jogging or cycling.
• Physically demanding jobs tend to be at the lower end of the pay scale. It's possible that people with these jobs do not have access to high-quality health care. Or they may have other disadvantages that impair health.

In any case, these studies suggest that people with physically demanding jobs should pay close attention to any risk factors for heart and blood vessel disease. The harder question is whether they should scale back their exercise routines. In my view, we need more research to answer that question.

What Changes Can I Make Now?

Whether your job is physically demanding or not, talk to your doctor about your risk factors for heart and blood vessel disease and what to do about them. For example:

• For high blood pressure or high cholesterol, do your best to lose excess weight and improve your diet. (See DASH diet for high blood pressure and a 'heart-smart' diet for high cholesterol). Medicines may be necessary.
• If you have diabetes, losing excess weight and changing your diet are the first steps. However, medicines also may be recommended. They may include aspirin and drugs to lower blood sugar and cholesterol.
• Don't smoke. If you have not managed to quit, talk to your doctor about smoking-cessation programs.
• If you have an irregular heart rhythm called atrial fibrillation, ask your doctor whether you should take a blood thinner.

The results of these new studies question the notion that all physical activity comes with the same health benefits. Still, I think it would be a mistake to use these studies as a reason to avoid exercise! This is especially true for those whose jobs are mostly done while sitting.

If your job is physically demanding, you may be getting more than enough exercise at work. Lower-intensity exercise, such as walking, may be better for you than higher-intensity activities. Talk to your doctor about your current fitness level and an exercise program that meets your needs.

What Can I Expect Looking to the Future?

Current advice suggests moderate-intensity exercise (such as brisk walking) for at least 45 minutes most days of the week. I think this is a good idea for most people. But we need to find out when more exercise may cause more harm than good. These two new studies are a good start. In the future, I hope we'll have more nuanced advice about exercise that takes into account the exercise people get at work.