Multimorbidity, physical function, and risk of falls in middle-aged adults

Physical function and multimorbidity are key risk factors for falls in middle-aged adults, but few studies have evaluated these associations in a longitudinal manner. In 3561 participants (1968 females, aged 45-69 years) from the Busselton Healthy Ageing Study, a longitudinal cohort study, we studied the associations of baseline multimorbidity count and patterns with physical function and the subsequent risk of falls at six years.

At baseline, 21 morbidities were assessed and four multimorbidity patterns were identified using latent class analysis. Physical function tests including hand grip-strength (HGS), timed up and go (TUAG) and five times sit to stand (5TSTS) were performed at Phase 1 (baseline) and Phase 2 (average six years) and falls occurring in the previous 12 months were captured through self-report at Phase 2. General linear models and logistic regression were used to evaluate associations, adjusting for sex and baseline covariates.

Mean physical function measures worsened by 6.0% to 23.7% between phases; 950 (26.7%) participants reported at least one fall and 383 (10.7%) reported multiple falls. Increasing multimorbidity count was associated with lower physical function at both phases, greater decline over time (HGS: -0.13 kg, TUAG: +0.08 s, 5TSTS: +0.14 s per unit increase), and greater risk of falling and among fallers having multiple falls (odds ratio (OR): 1.14 and 1.15 per unit increase, respectively). Among the multimorbidity classes, the "cardiometabolic" class had the lowest physical function at both phases and the greatest decline over time (2.8-8.8% greater vs "healthy"), whereas the "non-cardiometabolic" class showed the highest risk of falling and having multiple falls (OR: 1.79 and 2.16 vs "healthy", respectively). Associations with falls risk remained significant after further adjustment of physical function measures of either phase.

Our study underscores the importance of identifying multimorbidity as a risk factor for physical function decline and fall risk in middle-age.