Association between physical activity, occupational sitting time and mortality in a general population: An 18-year prospective survey in Tanushimaru, Japan

Abstract

Aims: It is well known that a decline in physical activity is associated with an increase of all-cause death including cardiovascular events and cancer. Few studies have examined the association between occupational sitting time and mortality. Therefore, we investigated this issue in a general population.

Methods: Physical activity and occupational sitting time were measured using the Baecke physical activity questionnaire in 1999. The questionnaire generated indices in three physical activity categories: work, sport and leisure-time. A total physical activity index was calculated by adding these three indices. The Baecke physical activity questionnaire was able to evaluate occupational sitting time. Hazard ratios and 95% confidence intervals (CIs) were calculated using Cox's proportional hazard regression models.

Results: We enrolled a total of 1680 participants, who were followed up for 15.9 ± 3.8 years. The final follow-up rate was 93%. During the follow-up period, 397 subjects died. A significant inverse association (p < 0.0001) was found between physical activity and mortality after adjustment for age and sex. Compared with lower levels of physical activity, the adjusted hazard ratio for mortality at higher levels of physical activity was 0.85 (95% CI: 0.78-0.92). Longer occupational sitting time was also significantly associated with higher mortality (p < 0.01). The adjusted hazard ratio for mortality at longer occupational sitting time was 1.16 (95% CI: 1.05-1.27). These findings were observed in males, but not in females.

Conclusions: Our data demonstrated that higher levels of physical activity are associated with a reduced risk of cancer and cardiovascular death. Further, longer occupational sitting time is associated with increased mortality.

Keywords: Physical activity; epidemiology; mortality; sitting time.