PAST AND PRESENT PHYSICAL-ACTIVITY AND ENDOMETRIAL CANCER RISK

We examined the relation between physical activity and endometrial can cer using data from a multicentre case-control study involving 405 end ometrial cancer cases and 297 population controls. Estimates of recrea tional (i.e. active sport, walks and hikes) and nonrecreational activi ty (i.e. house cleaning, climbing stairs and walking or standing on th e job) were obtained using interview information. After adjustment for age, study area, education, parity, years of use of oral contraceptiv es, years of use of menopausal oestrogens and cigarette smoking, recen t recreational inactivity was associated with increased risk (RR = 1.9 for lowest vs highest tertile). Similarly, recent nonrecreational ina ctivity was associated with increased risk (RR = 2.2 for lowest vs hig hest tertile). Further adjustment for body mass and nonrecreational ac tivity attenuated the association between risk and recent recreational inactivity (RR = 1.2; 95% CL = 0.7-2.0) but adjustment for body mass and recreational activity did not alter the association between risk a nd recent nonrecreational inactivity (RR = 2.0; 95% CL = 1.2-3.1). To evaluate the relation between risk and sustained inactivity, we simult aneously examined activity levels at three periods (i.e. age 20-29, ag e 30-39 and recently) in women age 50 and older. After adjustment for potential confounders and body mass, risk was elevated among women who were always recreationally inactive (RR = 1.5 for always active vs al ways inactive) and among women who were always nonrecreationally inact ive (RR = 1.6 for always active vs always inactive). This study sugges ts that physically inactive women may be at increased risk of endometr ial cancer because they are more likely to be overweight or obese. Our data also suggest that inactivity per se may be associated with an in creased risk of endometrial cancer. However, we cannot rule out the po ssibility that our results, particularly those for nonrecreational act ivity, reflect unmeasured confounding factors. Future studies should a ttempt to obtain more detailed assessments of physical activity, inclu ding the intensity with which an individual engaged in an activity and the actual time involved in exertion.