RISK FOR ENDOMETRIAL CANCER IN RELATION TO OCCUPATIONAL PHYSICAL-ACTIVITY - A NATIONWIDE COHORT STUDY IN SWEDEN

Notwithstanding its biologic plausibility, the association between phy sical activity and endometrial cancer has been analyzed in only a few epidemiological studies. Retrospective assessment of exposure and smal l sample size often hampers interpretation of published data. We studi ed risk for endometrial cancer in relation to physical activity at wor k in a large cohort of Swedish women identified in the nationwide cens uses in 1960 and 1970, with jobs that could be consistently classified into one of 4 levels of physical demands. Follow-up from 1971 through 1989 was accomplished through record linkages. Multivariate Poisson r egression models were used to estimate relative risk. The risk for end ometrial cancer increased regularly with decreasing level of occupatio nal physical activity ( p for trend < 0.001), and was associated more strongly with activity in 1970 than in 1960. In multivariate analyses, adjusted for age at follow-up, place of residence, calendar year of f ollow-up, and social class, the relative risk among women with the sam e physical activity level in 1960 and in 1970 was 30% higher for seden tary as compared with high/very high activity level; (p for trend = 0. 04). The protective effect of physical activity appeared to be confine d to women aged 50 to 69, among whom sedentary work was associated wit h a 60% higher risk than that observed among women estimated to be phy sically most active. The excess seemed to disappear within 10 years af ter a change in physical activity level. Although confounding cannot b e ruled out in our data, occupational physical activity appears to red uce the risk for endometrial cancer. (C) 1998 Wiley-Liss, Inc.