Abstract
PURPOSE: Although examining the dose-response curves of physical activity (PA) and sitting time with health-related outcomes is an important research agenda, the results for older Japanese adults are extremely limited. We examined the dose-response associations of PA and sitting time with all-cause mortality among older Japanese. METHODS: Initially, 8,069 non-disabled residents (4,073 men; 3,996 women) aged 65-84 years of Ota City, Japan, were analyzed. Moderate-to-vigorous PA (MVPA) and sitting time were evaluated using the International Physical Activity Questionnaire-Short Form. Multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of MVPA and sitting time for all-cause mortality were calculated, and the dose-response curves were examined using restricted cubic splines (RCS). RESULTS: During 4.1 years of follow-up, 458 participants (5.7%; 331 men and 127 women) died. Compared with the low MVPA (<600 metabolic equivalents [METs]·minutes/week) group, HR for mortality gradually reduced in moderate (600-3,000 METs·minutes/week) and high (>3,000 METs·minutes/week) MVPA groups (moderate: HR 0.66; 95% CI, 0.54-0.82; high: HR 0.58; 95% CI, 0.45-0.75; P < 0.001 for trend). RCS showed that the HR for mortality reduced linearly up to approximately 2,000 METs·minutes/week of MVPA, and maximal risk reduction was seen at approximately 3,000-4,500 METs·minutes/week of MVPA. No significant dose-response association of sitting time with mortality was observed. CONCLUSION: Higher MVPA levels reduced all-cause mortality risk, in a significant inverse non-linear dose-response manner. Sitting time was not significantly associated with all-cause mortality. It is important to disseminate the significance of even a slight increase in the MVPA for reducing mortality risk.