Sedentary Time in Older Adults: Absolute vs. Relative Measures and their Respective Association with Health conditions and Multimorbidity.

Older adults (OA) accumulate a greater amount of sedentary time (ST) compared to other subgroups of the population which is associated with deleterious effects on multiple health outcomes and mortality. This study compared absolute sedentary behavior time (ASBT), which is generally used in studies, to relative SB time (RSBT), defined as the percentage of daily wake time, for their respective association with health conditions and multimorbidity. Two-thousand-sixty-one older adults (65 to 79 years) participated in the Canadian Health Measures Survey (2007-2017) and worn an accelerometer for ≥ 4 days, including a weekend day. Information regarding six health conditions categories was extracted: cancer, cardiovascular, metabolic, musculoskeletal, psychological and pulmonary. We combined these health conditions to create a multimorbidity variable. Participants were divided into ASBT quartiles and RSBT quartiles. Comparing the most sedentary (Q4) to the least sedentary (Q1) groups, we found no significant associations with any health conditions for ASBT. However, the same comparison for RSBT showed that RSBT-Q4 (the most sedentary; n=660), compared to RSBT-Q1 (n=660), was associated with a significant (p<0.01) greater prevalence of cancer (160>110), cardiovascular (422>326), metabolic (276>194), and musculoskeletal (407>345), as well as multimorbidity (462>350). After adjusting for confounding factors (moderate to vigorous physical activity, housing, income, education level, relationship status, accelerometer wear season, and status of drinking and smoking), these associations persisted with the exception of musculoskeletal conditions. These results demonstrate that RSBT could be more appropriate to capture the association between a sedentary lifestyle and health profiles in older adults.