Multimorbidity Trajectories from Early to Middle Adulthood and Physical Activity.

Introduction: Multimorbidity is associated with lower physical function in older adults. Less is known about multimorbidity and physical activity earlier in the life-course. This study examined multimorbidity trajectories across adulthood with physical activity and explores if multimorbidity accelerates age-related activity decline.

Methods: Data are from Coronary Artery Risk Development in Young Adults (CARDIA), an ongoing prospective cohort of participants recruited when they were 18-30 years old. Six multimorbidity trajectories from baseline (1985-86) through year 30 follow-up exam (2015-16; ages 48-60) were based on age of disease onset and rate of accumulating additional conditions: mid-20s-fast, mid-20s-slow, late-20s-slow, mid-30s-fast, mid-40s-fast, and early-50s-slow. Activity was device-measured at year 30 and year 35 (2021-23; ages 53-65). Multivariable linear models were used to estimate differences in activity by multimorbidity trajectory at year 30 and change (%) from year 30 to year 35. Data were collected through June 2023 and analyzed in May 2024.

Results: The sample included 1,425 CARDIA adults at year 30 (mean age 55.1 years) with 749 (mean age 61.3 years) wearing the device again at year 35. Compared with early-50s-slow, mid-20s-slow (β=-14.1, 95%CI: -24.6, -3.6) and mid-30s-fast (β=-14.2, 95%CI: -26.2, -2.2) had lower LPA and mid-20s-fast (β=-5.1, 95%CI: -9.6, -0.6) and late-20s-fast (β=-9.5, 95%CI: -14.1, -4.9) had lower MVPA. No significant differences in 5-year behavior change across multimorbidity trajectories.

Conclusions: Early onset and faster accumulation of chronic conditions was associated with lower activity in midlife. Lower intensity activity for people with multimorbidity may be a feasible target for healthy aging.