Nonlinear association of higher-level functional capacity with the incidence of falls in Japan

OBJECTIVE: To examine the nonlinear association of higher-level functional capacity with the incidence of falls. DESIGN: We analyzed the cross-sectional data of Minamifurano-town Aging Study. Seven hundred forty-three noninstitutionalized older persons aged 65 yrs or older were mailed a self-administered questionnaire in June 2002 in which they were asked the incidence of falls in the past year and their higher-level functional capacity according to the Tokyo Metropolitan Institute of Gerontology (TMIG) index of competence. The association of higher-level functional capacity with the incidence of falls was examined using linear, polynomial, and nonparametric logistic regression models. RESULTS: Under the assumption of a nonlinear function, the quadratic function and the smoothing function provided a significant improvement of the fit compared with the linear model in women but not men. CONCLUSION: We have proposed the use of nonlinear model in estimating the incidence of falls with respect to the total score of the TMIG index of competence. The association of varying total score with the incidence of falls in women diverged from the linearity assumption. The gender-based difference in the association of higher-level functional capacity with the incidence of falls might be related to societal role or activity-related aspects.