Dose-response Association between Hand Dexterity and Functional Disability: A Longitudinal Study from the Kasama Study.

Background: Poor hand dexterity may increase the risk of functional disability; however, few studies have examined the relationship between hand dexterity and incident functional disability. The aim of this study was to prospectively investigate the dose-response association of hand dexterity with incident functional disability in community-dwelling older adults.

Methods: This study included 1,069 older adults aged ≥65 years in Kasama City, Japan. Peg-moving and circle-drawing tasks were used to evaluate hand dexterity. Functional disability was identified using the Japanese Long-Term Care Insurance System database. Restricted cubic spline analysis was performed to investigate the dose-response association between hand dexterity and incident functional disability.

Results: During a mean follow-up of 8.5 years (maximum 14.0 years), 248 participants (23.2%) developed functional disability. The lowest performance group in each hand dexterity test had a significantly higher risk of functional disability than the highest performance group (peg-moving: HR = 1.92, 95% CI = 1.29-2.87; circle drawing: HR = 1.66, 95% CI = 1.15-2.41). Spline analysis confirmed curvilinear dose-response associations between hand dexterity and incident functional disability. Increased risk was observed when participants performed worse than the cut points (peg-moving: 37.9/38.0 seconds; circle drawing: 21/20 points), and no decreased risk was observed for those who performed better than these cut points.

Conclusion: Easily evaluated hand dexterity tests may be valuable for predicting functional disability in older adults. Curvilinear dose-response associations suggest that maintaining adequate hand dexterity could be a key strategy to support functional independence.