Endocrine Abstracts

JOINT1825

Background: Obese individuals tend to lead sedentary lifestyles and avoid physical activity (PA). It remains unclear whether increasing PA can offset the health risks associated with sedentary behavior (SB), as well as the intensity of PA required to achieve such an effect.

Objectives: This study aimed to evaluate the joint and stratified associations of SB and PA with all-cause, cancer, and cardiovascular disease (CVD) mortality, and to estimate the theoretical effects of replacing SB with sleep or PA.

Methods: A total of 90,971 adults with obesity from the UK Biobank were included in the analysis. Information on sedentary time (sum of television watching, computer using and driving behavior) and PA (measured by International Physical Activity Questionnaire) were collected by self-reported at baseline. Participants were followed up for mortality events according to the ICD-10 code using linkage to national health records until 2021. Cox proportional hazards regression models were used to calculate multivariable-adjusted hazard ratios (HRs) for each SB-PA combination group and within SB strata. The isotemporal substitution model was applied to investigate the impact of replacing SB with sleep, walking, moderate physical activity (MPA), and vigorous physical activity (VPA), adjusting for potential confounders.

Results: During a median follow-up of 12.7 years, 8,357 deaths occurred, including 1,784 from CVD and 2,673 from cancer. Among groups with no PA, reducing sedentary time was not significantly associated with all-cause or cancer mortality. Compared with the reference group (no PA and SB >8 h/day), the group with VPA and 4–8 h/day of SB exhibited the lowest all-cause mortality risk (HR 0.70, 95% CI 0.65–0.75). The group with VPA and <4 h/day of SB showed the lowest cancer mortality risk (HR 0.68, 95% CI 0.60–0.78), while the group with VPA and >8 h/day of SB had the lowest CVD mortality risk (HR 0.66, 95% CI 0.57–0.78). Across SB subgroups, increased PA was significantly associated with reduced all-cause and cause-specific mortality, demonstrating an almost dose-response relationship. Replacing SB with walking or VPA showed stronger associations, with mortality risk declining as the replacement duration increased. For example, replacing 3 h of SB with an equivalent amount of VPA reduced all-cause mortality (HR 0.80, 95% CI 0.77–0.84).

Conclusions: In adults with obesity, reducing sedentary time and increasing PA of any Intensity are significantly associated with lower risks of all-cause and cause-specific mortality. Increasing PA or replacing SB with PA attenuates the association between SB and mortality.