Sedenatry Occupation, Its Validity and Risk for Colon Cancer

Abstract

Although sedentary occupation has become more common, it is still uncertain how much physical activity spent at work contributes to total energy expenditure (TEE) and health outcomes. PURPOSE: The primary objective of this study is to examine the relationship between posture at work and TEE by the DLW method as a gold standard. The secondary objective is to investigate the relationship between posture at work and cancer incidence. METHODS: 1) Study participants were 226 Japanese men and women aged 20 to 83 years. TEE and TEE per unit weight (TEE/BW) were estimated over one or two weeks depending on the two half-lives of the isotopes using the DLW method. The posture at work, which is a component of our physical activity questionnaire (JALPAQ), was surveyed for every participant before DLW dosing. 2) We asked similar questions about physical activity of 7,796 urban male workers aged 35-59 who participated in periodic health check-up between 1988 and 1990. Subjects were followed till the end of December, 1994, and a total of 123 cancers (and 36 colon cancers) were identified during the period by Osaka Cancer Registry. Cox proportional hazards models were used to estimate age-adjusted relative risks (RR) and 95% confidence intervals (CI). RESULTS: The posture at work was most closely related with TEE/BW, and there was the dose-response relationship between the posture and TEE/BW. The relation of the posture at work with all-cause cancer appeared to be U-shaped. Compared to those who were almost sitting, those who were standing more frequently had a significantly lower risk (RR = 0.46, CI = 0.22-0.98). There seemed to be dose-response relationships between the posture and colon cancer. Compared to those who were almost sitting, RRs (CI) for those who were sitting more frequently, sitting for half of work time, standing more frequently, and almost standing were 0.50(0.20-1.28), 0.59(0.24-1.44), 0.45(0.13-1.54), and 0.27(0.09-0.83), respectively. CONCLUSIONS: These data suggest that the posture at work is a simple and useful question item to estimate a TEE, and the sedentary lifestyle may be one of strong risk factors for colon cancer among Japanese male workers.