June 1, 2009 (Seattle, Washington) — Moderate to vigorous physical activity during young adulthood may help offset the increased risk for prostate cancer in black men, according to a study presented here at the annual meeting of the American College of Sports Medicine.
In the National Institutes of Health-AARP Diet and Health Study, black men between the ages of 51 and 72 years were significantly less likely to develop prostate cancer within a 7-year period if they reported having been physically active during their 20s. A similar but nonsignificant trend was seen for black men who reported having been physically active in their late 30s.
The findings suggest that interventions designed to improve physical fitness in young black men could eventually lower the incidence of prostate cancer in that population, which has been reported to be 30% to 50% higher than in white men. Prostate cancer has also been shown to be more aggressive in black men, with a death rate twice that of white men.
"Obviously this is great news," Steven C. Moore, PhD, a postdoctoral fellow in the Nutritional Epidemiology Branch of the National Cancer Institute's Division of Cancer Epidemiology and Genetics, said during his presention. "Black men suffer disproportionately from this disease, and there have been no known modifiable risk factors."
More than 160,000 white men and 3671 black men completed a 1996 questionnaire about their physical activity history. The questionnaire asked about the number of hours per week spent on moderate to vigorous activity, such as biking, fast walking, aerobics, or jogging. In the next 7 years, 9624 white men and 371 black men were diagnosed with prostate cancer.
Physical activity was not significantly associated with prostate cancer risk in the white men. However, the black men who reported at least 4 hours of physical activity per week between the ages of 19 and 29 years were 35% less likely to develop prostate cancer (P = .01). More than 7 hours a week of physical activity between the ages of 35 and 39 years was associated with a 41% lower risk, although that finding fell short of statistical significance (P = .15).
The apparent protective effect of physical activity may be related to race-specific differences in tumor immunobiology, as suggested in a 2008 National Institutes of Health study published in Cancer Research.
"Tumors seem to be different in black men," Dr. Moore said. "Physical activity influences both immune function and inflammation, which play a larger role in the tumors of black men."
Nutrition May Also Play Role
Further analysis of the data, not presented at the meeting, suggest that nutrition may also play a role, Dr. Moore added.
"The effects seem to be primarily related to younger men, who would have been born around the time of the Great Depression. The unemployment rate among black men at that time was somewhere north of 30%, so there was some significant caloric restriction in that population," he said.
A limitation of the study was that it relied on patient recall. In addition, the population was drawn from an AARP database that is biased toward college-educated individuals, which may not be an accurate representation of black men in the targeted age group. Lower socioeconomic demographics have been associated with higher risks for prostate cancer.
Nevertheless, the findings could represent a significant step toward prostate cancer prevention, said Kathleen Y. Wolin, ScD, assistant professor of surgery at Washington University School of Medicine in St. Louis.
"The results are really exciting," said Dr. Wolin, who presented during the same session on a possible association between physical activity level and incontinence after prostatectomy. "We don't have a lot of data on things men can do to prevent prostate cancer, and it's a particular concern in black men, so I think the findings will have intriguing and compelling implications for interventions in the future."
Dr. Wolin noted that, given that both black men and obese men have increased risks for aggressive prostate cancer, it would be particularly helpful for future research to investigate the effect of physical activity on prostate cancer mortality as well as incidence.
The study did not receive commercial support. Dr. Moore disclosed no relevant financial relationships.
American College of Sports Medicine (ACSM) 57th Annual Meeting: Abstract 885. Presented May 29, 2009.
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Cite this: ACSM 2009: Exercise May Lower Prostate Cancer Risk in Black Men - Medscape - Jun 01, 2009.