Relating wrist accelerometry measures to disability in older adults

Objective: This analysis assessed the extent to which: (1) wrist accelerometer measures were associated with difficulty performing specific activities of daily living and instrumental activities of daily living and (2) these measures contributed important information about disability beyond a typical self-reported vigorous activity frequency question. Methods: We used data from the National Social Life, Health and Aging Project (NSHAP) accelerometry sub-study (. n=. 738). Activity was assessed using two wrist-accelerometer measures assessed over 3 days (routine activity expressed as mean count/15. s epoch during wake time, and immobile time expressed as the proportion of wake time spent immobile), and self-reported average vigorous activity frequency. The association between routine activity, immobile time and difficulty performing fourteen activities of daily living (ADLs) and instrumental activities of daily living (IADLs) plus two summary measures (any ADL or IADL difficulty), was assessed using logistic regression models, with and without controlling for self-reported vigorous activity. Results: Self-reported activity was mildly correlated with routine activity (. r=. 0.27) and immobile time (. r=. -0.21). Routine activity, immobile time, and self-reported vigorous activity were significantly associated with twelve, ten, and fourteen disability measures, respectively. After controlling for self-reported activity, significant associations remained between routine activity and eight disabilities, and immobile time and six disabilities. Conclusion: Wrist accelerometry measures were associated with many ADL and IADL disabilities among older adults. Wrist acclerometry in older adults may be useful to help assess disability risks and set individualized physical activity targets.