News Review From Harvard Medical School — Fitness May Reduce Lung, Colon Cancer Risk

April 2, 2015

Men who are fit in middle age may have lower risks of some cancers in later years, a new study finds. The study included nearly 14,000 men who were part of a long-term health study. Their average age when the study began was 49. Nearly all were white. Men were given treadmill tests to assess their fitness. After the men turned 65, researchers looked at Medicare records to see who was diagnosed with cancer. On average, they looked at 6½ years of records for each man. Men who had the top fitness scores in middle age were 55% less likely to develop lung cancer than those who were least fit. They were 44% less likely to develop colorectal cancer. But they were 22% more likely than less fit men to be diagnosed with prostate cancer. The men who were most fit also had a 32% lower rate of death from lung, colorectal or prostate cancer. They also were 68% less likely to die of heart disease or stroke after being diagnosed with cancer. The journal JAMA Oncology published the study. HealthDay News wrote about it March 26.

By Robert H. Shmerling, M.D.

Harvard Medical School

What Is the Doctor’s Reaction?

Exercise is good for you.

You’ve probably heard this many times before. You may even be tired of hearing it. But it’s hard to ignore the simple truth that exercise is one of the best things you can do for your health.

The list of ways exercise can improve your health is long. And it’s getting longer. For example, regular exercise may be helpful to treat or prevent:

Heart and artery disease (including heart attack and stroke)

It’s an impressive list. But did you know that exercise may also reduce the risk of certain types of cancer? And those who are physically active may survive longer once a cancer is diagnosed. For example, a 2010 study found that among women with breast cancer, those who were most active tended to live longer.

A new study provides some of the best evidence to date that exercise and physical fitness during midlife can affect cancer risk and cancer-related death decades later.

Researchers enrolled nearly 14,000 men with an average age of 49. Each man had a treadmill test to assess physical fitness. Then researchers kept track of the men for several decades to see who developed prostate, lung or colorectal cancer. Researchers also looked at the causes of death among men 65 and older who developed these cancers.

The results suggest a dramatic benefit related to exercise. Compared with those who were the least fit, those who were most fit had:

A 55% lower risk of lung cancer
A 44% lower risk of colon cancer
A 32% lower risk of cancer-related death
A 68% lower risk of death from heart and artery disease after the diagnosis of cancer

But not all cancers studied were lower among the most fit. The risk of prostate cancer was actually 22% higher in this group.

The results of this study suggest that physical fitness may reduce the risk of certain cancers. But you should not rely on exercise alone to prevent cancer. And the finding of a higher risk of prostate cancer certainly deserves more study.

What Changes Can I Make Now?

This study is only the latest to suggest that it’s a good idea to increase your physical fitness.

Think about how much exercise you are getting and what may be keeping you from getting more. Some commonly reported barriers and changes you can make to overcome them include:

“I don’t have enough time.” You can increase your physical activity in ways that take little or no time. For example, meet with a colleague while walking instead of sitting in a conference room. Take the stairs instead of the elevator. You may even save time by not waiting for the elevator.
“Exercise is uncomfortable (or painful).” Certain conditions, such as arthritis or lung disease, can make it unpleasant to exercise. If discomfort is a problem for you, be sure to start slowly. With the guidance of a physical therapist or an experienced trainer, it’s usually possible to get past the discomfort. For example, people with arthritis often tolerate exercise well if they do it in a pool.
“Exercise is boring.” Use exercise to explore what’s around you. For example, walking or jogging is a great way to learn about new places while traveling. Or you could exercise while watching TV or listening to music. An “exercise buddy” can transform physical activity into a social event.
“Exercise is expensive.” This can be true if you’re paying for a health club. But some of the best exercise is free (such as walking or jogging). Other types require only a modest investment, such as buying a bicycle.

Of course, exercise isn’t the only thing you can do to lower your risk of cancer. Talk to your doctor about lifestyle changes (such as quitting smoking) and screening tests (such as colonoscopy). They can lower your risk of cancer or promote early detection.

What Can I Expect Looking to the Future?

This study is powerful evidence that being physically fit during midlife may protect against certain types of cancer. However, it also raises several important questions. They include:

Does physical fitness protect women or nonwhite men against cancer? This study included only men, and nearly all were white.
Does fitness protect against other types of cancer? This study examined the impact of exercise only on cancers of the prostate, lung and colon.
How does exercise protect against cancer? This study did not look at why lung and colon cancer rates were lower among those who were most fit.

Perhaps the most important question raised by this research is also the hardest to answer: How can we get people to improve their physical fitness? Perhaps the results of this study will help.

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