Physical Performance Predictors for Incident Dementia Among Japanese Community-Dwelling Older Adults

Background. Evaluating physical performance could facilitate dementia risk assessment. However, findings differ regarding which type of physical performance best predicts dementia. Objective. The objective of this study was to examine the association between physical performance and incidence of dementia in Japanese community-dwelling older adults. Design. This was a prospective study of community-dwelling older adults. Methods. Of 14,313 invited individuals who were >= 65 years old, 5104 agreed to participate from 2011 to 2012, and 4086 (52% women; mean age = 72.0 years) met the criteria. Baseline assessments of the following physical performance indicators were obtained: grip strength, the Five-Times Sit-to-Stand Test, and the Timed Up & Go Test. The physical performance level in each test was categorized as C1 (highest), C2 (middle-high), C3 (middle-low), or C4 (lowest) on the basis of sex-stratified quartile values. Incident dementia status was obtained from medical records that were updated monthly. Results. During follow-up (mean duration = 42.9 months), there were 243 incident cases of dementia (5.9%). Log-rank test results indicated that a lower physical performance level constituted a significant risk factor for dementia. After adjustment for covariates, Cox proportional hazards models (reference: highest physical performance level [C1]) demonstrated that the Five-Times Sit-to-Stand Test in the group with the lowest physical performance level (hazard ratio = 1.69; 95% CI = 1.10-2.59) was significantly associated with a risk of dementia. Likewise, the Timed Up & Go Test in the group with the lowest physical performance level (hazard ratio = 1.54; 95% CI = 1.01-2.35) was significantly associated with a risk of dementia. However, grip strength was not significantly associated with a risk of dementia. Limitations. This study was limited by the use of medical record data. Conclusions. A lower mobility-related physical performance level was associated with dementia risk. Dementia risk assessment should include an adequate evaluation of physical function.