Physical Activity and Risk of Prostatic Cancer among College Alumni

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Abstract
Clinical observations and laboratory experiments have suggested a role for testosterone in the development of prostatic cancer. Since physical training may act to lower testosterone levels, men who are very active may have a reduced risk of this cancer. To test this hypothesis, the authors prospectively followed 17,719 Harvard alumni (aged 30–79 years) from 1965 or 1969 to 1977, and 1980 to 1988 for the occurrence of prostatic cancer (n = 419). Physical activity was assessed in either 1962 or 1966, and again in 1977, based on self–reported stair climbing, walking, and sports played. Alumni who expended greater than 4,000 kcal/week at both assessments were at reduced risk of developing prostatic cancer (age–adjusted rate ratio, 0.12; 95% confidence interval 0.02–0.89) compared with their inactive counterparts who expended less than 1,000 kcal/week at both assessments. These results should be interpreted cautiously, since only one case of prostatic cancer was identified among alumni highly active at both assessments, who contributed 4% of total person–years to the analysis. Among alumni aged 70 years and older, those who expended greater than 4,000 kcal/week at either assessment had about half the risk of those who expended less than 1,000 kcal/week at either assessment (age–adjusted rate ratio, 0.53; 95% confidence interval 0.29–0.95). The authors attribute these findings to the increased precision with which physical activity could be measured when combining two activity assessments. Alternatively, long-term maintenance of a high level of physical activity may be necessary for further reduction of risk. There was no evidence of a dose–response relation. Am J Epidemiol 1992;135:169–79.

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