The relationship between cognitive function and physical performance in older women: results from the women's health initiative memory study.

BACKGROUND Cognitive function and physical performance are associated, but the common sequence of cognitive and physical decline remains unclear. METHODS In the Women's Health Initiative Memory Study (WHIMS) clinical trial, we examined associations at baseline and over a 6-year follow-up period between the Modified Mini-Mental State (3MS) Examination and three physical performance measures (PPMs): gait speed (meters/second), chair stands (number of stands in 15 seconds), and grip strength (kilograms). Using mixed models, we examined the baseline 3MS as predictor of change in PPM, change in the 3MS as predictor of change in PPM, and baseline PPM as predictors of 3MS change. RESULTS Among 1,793 women (mean age = 70.3 years, 89% white, and mean 3MS score = 95.1), PPM were weakly correlated with 3MS-gait speed: r = .06, p = .02; chair stands: r = .09, p < .001; and grip strength: r = .10, p < .001. Baseline 3MS score was associated with subsequent PPM decline after adjustment for demographics, comorbid conditions, medications, and lifestyle factors. For every SD (4.2 points) higher 3MS score, 0.04 SD (0.04 m/s) less gait speed and 0.05 SD (0.29 kg) less grip strength decline is expected over 6 years (p </= .01 both). Changes in 3MS and PPM were associated, particularly with chair stands and grip strength (p < .003 both). Baseline PPMs were not associated with subsequent 3MS change. CONCLUSIONS Baseline global cognitive function and change in global cognitive function were associated with physical performance change, but baseline physical performance was not associated with cognitive change in this cohort. These analyses support the hypothesis that cognitive decline on average precedes or co-occurs with physical performance decline.