Exercise May Cut Prostate Cancer Risk
WASHINGTON — Aerobic exercise may reduce the risk of prostate cancer--and the more exercise, the greater the reduction, researchers say.
A look at data on 12,975 men found that those who exercised the most were most likely to be free of prostate cancer when their health was reviewed later.
The researchers studied men with an average age of 44 who had received physical exams at the Cooper Clinic in Dallas from 1970-89. All had taken a treadmill test to assess their fitness. The men were sent questionnaires mailed in 1982 and 1990 to see if they had developed prostate cancer. The researchers found 94 cases of prostate cancer, including six deaths.
The men also were asked what physical activity they may have been involved in regularly during the last three months, and how hard they worked at it.
Researchers then converted the men’s treadmill results, activity habits and weights into calories burned per week in exercise.
The results were reported in the January issue of the American College of Sports Medicine’s journal, Medicine and Science in Sports and Exercise.
In both groups, those who had moderate or high exercise levels had lower cancer rates than those who did little or no exercise. The moderate-exercise group had about three-quarters of the risk faced by those who did little or no exercise. The high exercise group had about 30% of the risk.
“It appeared that even moderate exercise levels were protective,†said researcher Susan Oliveria, director of epidemiology at the Strang Cancer Prevention Center in New York City.
Oliveria emphasized the apparent value of doing at least moderate activity. Although the high-activity group had a sharply lower risk, there were fewer people in this group, so individual differences could make the margin of error greater.
Because the study combined varied forms of exercise into percentile scores, Oliveria could not point to benefits of specific types of workouts. But the high-intensity group burned at least 3,000 calories a week by working out, and those who were considered moderate exercisers burned 2,000-3,000 calories.
The study is the first to link aerobic activity to reduced prostate cancer risk. In addition, it fits a pattern indicating that exercise can reduce the risk of prostate cancer, but it does not amount to proof, Oliveria said.
The latest report is more specific than earlier work in the Harvard Alumni Health Study, in which men reported what their activities were. The Harvard study found no benefit with less than 4,000 calories of exercise a week, said researcher I-Min Lee.
“That is a fair amount of exercise,†Lee said. It would amount to 10-12 hours a week of walking at 3-4 miles per hour, or seven hours a week of running at six miles per hour, she said.
Moderate activity levels of 2,000 calories would require half that.
Researchers can only speculate about why exercise might reduce the risk, but it’s possible that it works by reducing levels of the sex hormone testosterone, Oliveria said. Studies of athletes have found that testosterone drops after exercise, and studies of lab animals have found that those with lower testosterone had lower prostate cancer risk, she said.
“What it tells me as an epidemiologist is, yes, there is something going on, although we have to be skeptical,†Oliveria said, adding that it’s too early in the research to reach a conclusion.
