Age-Dependent Nonlinear Association Between Gait Impairment and Incident Dementia.

Abstract (English)

BACKGROUND AND OBJECTIVES: Gait impairment is associated with incident dementia, yet whether this association varies with age or follows a linear dose-response relationship remains unclear. The aim of this study was to examine the nonlinear dose-response relationship between Performance-Oriented Mobility Assessment (POMA) gait performance and incident dementia and to test whether this association is modified by age. METHODS: This prospective cohort study used data from the Korean Longitudinal Study on Cognitive Aging and Dementia (baseline enrollment, 2010-2012; follow-up through 2020; median follow-up, 6.2 years). The primary outcome was incident dementia diagnosed by Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) criteria. Gait and balance were assessed using the POMA. Cause-specific Cox proportional hazards regression with death treated as a competing event was used. Restricted cubic splines (RCS) modeled the nonlinear dose-response relationship between gait performance and incident dementia, and RCS-by-age interaction terms were used to test age modification and estimate age-specific hazard ratios and 95% CIs. RESULTS: Of 6,818 eligible participants, 4,822 met inclusion criteria (mean (SD) age, 69.6 (6.3) years; 2,719 (56.4%) female; median follow-up 6.2 years [IQR, 3.8-8.1]). During follow-up, 251 developed dementia and 458 died. The gait-dementia association was significantly nonlinear (<i>p</i> = 0.002), with hazard ratios rising steeply as scores departed from the ceiling and peaking near 9 to 10, below which estimates were imprecise. The association was strongly and inversely modified by age (interaction <i>p</i> < 0.001), indicating that the predictive value of gait deficits for dementia progressively diminishes with advancing age: the hazard ratio for a gait score of 11 vs 12 was 3.13 (95% CI 1.82-5.37) at age 65 years, 1.36 (95% CI 0.98-1.87) at age 75 years, and 0.59 (95% CI 0.37-0.94) at age 85 years. The estimated crossing age was 78.6 years. The age-dependent attenuation was specific to gait and not observed for balance in models including both components. DISCUSSION: Gait impairment predicted incident dementia in a nonlinear, age-dependent manner, with the association strongest in adults aged 65-75 years and not evident beyond approximately age 80 years. These findings suggest gait assessment may be most informative for dementia screening in younger-old adults. Limitations include an ethnically homogeneous cohort.