Association of insulin-like growth factor-1 with mild cognitive impairment and slow gait speed.

The decrease in serum insulin-like growth factor-1 (IGF-I) with aging is related to the neurobiological processes in Alzheimer's disease. IGF-1 mediates effects of physical exercise on the brain, and cognition has a common pathophysiology with physical function, particularly with gait. The aim of this study was to examine whether mild cognitive impairment (MCI) and slow gait are associated with the serum IGF-1 level. A population survey was conducted in 3355 participants (mean age, 71.4 years). Cognitive functions (attention, executive function, processing speed, visuospatial skill, and memory), gait speed, and demographic variables were measured. All cognitive functions and gait speed were associated with the IGF-1 level (p < 0.001). The association of IGF-1 with slow gait was weakened by adjustment for covariates, but MCI and the combination of MCI and slow gait were independently related to the IGF-1 level in multivariate analysis (p < 0.05). Our findings support the association of a low IGF-1 level with reduced cognitive function and gait speed, particularly with a combination of MCI and slow gait.