Lifetime occupational physical activity and incidental prostate cancer (Canada).
OBJECTIVES: The objective of this study was to assess the risk of incidental prostate cancer associated with occupational physical activity in a population of patients treated for benign prostatic hyperplasia (BPH) by transurethral resection of the prostate (TURP). METHODS: This case-control study was conducted in men aged 45 and over referred for TURP to relieve the symptoms of BPH in one of the eight hospitals of the Quebec City area between October 1990 and December 1992. Cases (n = 64) were all men incidentally diagnosed with prostate cancer and controls were the 546 patients with solely a histological diagnosis of BPH. At the time of their interview, the patients completed a diet history questionnaire and a general questionnaire including a lifetime occupational history. Physical activity was estimated for each job according to data from the US Department of Labor. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) of incidental prostate cancer associated with occupational physical activity while adjusting for confounders. RESULTS: A positive association was observed between "ever having a job with sedentary/light work" and incidental prostate cancer (OR = 1.9; 95% CI = 1.1-3.3). ORs for prostate cancer associated with 0%, 1-49%, and > or =50% of life spent in jobs with sedentary/light work were 1.0, 1.6 (95% CI = 0.8-3.1), and 2.5 (95% CI = 1.2-5.2), respectively (p-value for trend = 0.01). Occupational physical activity in the job held during the longest period was inversely associated with prostate cancer: ORs were 1.0, 0.5 (95% CI = 0.2-1.2), 0.4 (95% CI = 0.2-0.9) and 0.2 (95% CI = 0.1-0.7) for sedentary, light, moderate, and high/very high levels, respectively (p-value for trend = 0.008). CONCLUSIONS: The results of this study suggest that physical activity at work could have a beneficial effect on the occurrence of prostate cancer.