Methods: Comprehensive searches for prospective cohort studies providing effect estimates of objectively-assessed LPA (exposure) on all-cause mortality (outcome) were undertaken in five databases (PubMed, Medline, Scopus, Web of Science, and Google Scholar) up to 30 September 2018. This included contacting the authors of relevant studies for re-analyzing data to meet the selection criteria. Subgroup analyses and meta-regression analyses with random-effects models were performed to quantify the dose-response relationships between daily LPA and all-cause mortality. Sensitivity analyses were also conducted to assess the stability of the results.
Results: According to the pooled data from 11 eligible studies, LPA occupies a large amount of overall wake time in daily life (total weighted average of LPA: 5.01 hours a day). The subgroup analysis demonstrated that more time spent in daily LPA is progressively associated with lower risks of all-cause mortality. In comparison with the reference group (< 3 hours/day), the pooled HRs (and 95% CIs) of mortality were 0.71 (0.62-0.82) for the group (3-< 5 hours/day), 0.68 (0.59-0.79) for the group (5-< 7 hours/day), and 0.56 (0.44–0.71) for those spent time in LPA equal or more than 7 hours a day. Meta-regression models indicated that there was a log-cubic dose-response relationship between daily LPA and all-cause mortality in adults and older adults, which was independent of MVPA. The meta-regression analysis also indicated that the study-level factors, such as mean age of the sample (< 65 vs. 65+) and other factors, were not significant moderators of the relationships between LPA and death risks.
Conclusions: More time spent in daily LPA is associated with reduced risks of all-cause mortality. LPA can confer the health benefit for adults, and the positive health effect is sustainable at older ages. Adults and older people should be encouraged to spend more time in daily LPA. We hope these findings will provide additional evidence that supports the inclusion of LPA in the future physical activity guidelines.