Occupational physical activity and risk for prostate cancer in a nationwide cohort study in Sweden

Abstract

We investigated effects of occupational physical activity on relative risk for prostate cancer. From Swedish nationwide censuses in 1960 and 1970, we defined two cohorts of men whose occupational titles allowed classification of physical activity levels at work in 1960 (n=1 348 971) and in 1970 (n=1 377 629). A third cohort included only men whose jobs required a similar level of physical activity in both 1960 and 1970 (n=673 443). The incidence of prostate cancer between 1971 and 1989 was ascertained through record linkage to the Swedish Cancer Register. A total of 43 836, 28 702, and 19 670 prostate cancers, respectively, occurred in the three cohorts. In all three cohorts, the relative risk for prostate cancer increased with decreasing level of occupational physical activity (P50.001), using Poisson regression. Among men with the same physical activity levels in 1960 and 1970, the rate ratio was 1.11 for men with sedentary jobs as compared with those whose jobs had very high/high activity levels after adjustment for age at follow-up, calendar year of follow-up and place of residence (95% CI 1.05 -1.17; P for trend 50.001). There was no association between occupational activity and prostate cancer mortality. Since we had no data on other potential risk factors the observed associations for both incidence and mortality might have been confounded. Further studies are needed to better understand the potential role of physical activity for prostate cancer. Keywords: prostatic neoplasms; occupational physical activity; exercise; cohort studies; risk factors Prostate cancer is the most common cancer among Swedish men (31.5% of all cancer cases in men in 1999 and incidence rate 159 per 100 000) and the incidence rate has been steadily increasing since the 1960s (The Swedish Cancer Registry, 2001). The causes of prostate cancer are not clearly understood and genetic and environmental/life style factors seem to be important (Ross and Schottenfeld, 1996).Epidemiological studies of physical activity and prostate cancer risk have been inconclusive, but suggest a protective effect with higher levels of activity (Friedenreich and Thune, 2001). The theory is biologically plausible since physical activity may affect serum levels of testosterone and insulin-like growth factor I (IGF-I) and regulate the immune system (Chan et al, 1998b;McTiernan et al, 1998;Friedenreich and Thune, 2001). Moreover, physical activity might alter prostate cancer risk indirectly, by influencing body weight . In a prospective study, both cardiorespiratory fitness and self-reported history of sports activities were inversely related to prostate cancer risk (Oliveria et al, 1996).We used the nationwide, Swedish Cancer-Environment Register 60/70, to assess risk for prostate cancer in relation to occupational physical activity. We focused on men employed in 1960, and in 1970, with special attention given to men with the same level of occupational physical activity at these two assessments 10 years apart. The large number of observed prostate cancer case...

Physical activity and risk of prostate cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

“…Our result of no overall inverse association between occupational activity and prostate cancer is consistent with most, 12,16,[19][20][21][22][23][24][25] but not all, [5][6][7]13 previous studies. That physical activity is more strongly, inversely related to risk of advanced, high-grade or aggressive prostate cancer has, however, been indicated previously.…”

“…' 2009 UICC cancer is inconsistent, and in a new report from World Cancer Research Fund and American Institute for Cancer Research the expert panel concludes that the evidence for an association between physical activity and prostate cancer is too limited for a formal judgment. 3 Of the 22 published cohort studies, 9 found an inverse association of prostate cancer risk with cardiorespiratory fitness, 4 occupational activity, 5,6 leisure time activity [7][8][9][10][11] or both leisure time activity and occupational activity. 12 One study found an increased risk of prostate cancer among college athletes 13 and 12 studies found no significant association.…”

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“…often represent a great range of possible chemicals and exposure levels. Industry-based studies that can access employment records and other data sources for exposure assessment and allow the creation of a job exposure matrix (JEM) usually improve exposure assessment [Goldberg et al, 1993]; but such studies often do not have access to or are unable to collect information on potential non-occupational confounding risk factors [Dosemeci et al, 1993;Hsing et al, 1994;Krstev et al, 1998;Buxton et al, 1999;Brown and Delzell, 2000;Norman et al, 2002].…”

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