Association of Oral Hypofunction with Reduced Hand Dexterity in Community-Dwelling Older Adults: A Cross-Sectional...

Oral function and hand dexterity are related to cognitive function; however, no previous studies have explored their direct relationship. Considering the increasing prevalence of dementia and mild cognitive impairment (MCI), elucidating the relationship between these motor functions may contribute to early screening strategies. Thus, this study aimed to investigate the association between oral function and hand dexterity, and to examine whether this association is independent of sarcopenia-related factors.

From the 1044 participants from the 2017 Iwaki Health Promotion Project, we obtained 419 individuals aged ≥60 years (170 men, 249 women) after excluding participants with missing values. Oral function was assessed based on remaining teeth, tongue pressure, and oral diadochokinesis, and an oral hypofunction score (0-3 points) established. Hand dexterity was evaluated using the Purdue Pegboard Test (PPT) across the following four items: right hand, left hand, both hands, and assembly. The relationship between oral function and hand dexterity was analyzed using multiple regression.

Kruskal-Wallis tests revealed that higher oral hypofunction scores were associated with fewer pegs placed (all p < 0.001). Multiple regression (Model 1, n = 419) revealed significant associations between oral hypofunction score and all PPT items (unstandardized B = -0.49 to -0.23, all p ≤ 0.011). After adjusting for sarcopenia-related factors (Model 2, n = 294), associations remained significant for simple tasks (right hand B = -0.45, p = 0.002; left hand B = -0.33, p = 0.010) but not for complex tasks (both hands p = 0.080; assembly p = 0.161).

This cross-sectional study demonstrated that decline in oral function is partially independent of sarcopenia-related factors and associated with reduced hand dexterity, specifically in simple motor tasks.