Insulin-Like Growth Factor-1 Related to Disability Among Older Adults

Disability is a crucial health problem in aging. Identifying a biological contributory factor would be useful. Serum insulin-like growth factor-1 (IGF-1) plays an important role in the endocrine system and is associated with frailty. However, there is no consensus about the relationship between IGF-1 and disability. This study aimed to examine whether IGF-1 related to incident disability among older adults. The study included 4,133 older adults (mean age, 71.8 +/- 5.4 years) who were participants in the Obu Study of Health Promotion for the Elderly cohort study. We collected information on demographic variables, measured gait speed, Mini Mental State Examination score, and serum IGF-1 at baseline. During follow-up, incident disability was monitored by Long-Term Care Insurance certification. Disability was observed in 212 participants during a mean follow-up duration period of 29.2 months. A log rank test indicated that lower levels of serum IGF-1 were related to incident disability (p = .004). A Cox hazard regression showed a lower quartile in IGF-1 related to disability compared with the highest quartile (Q4), even when adjusting for covariates including gait speed and Mini Mental State Examination score (Q1: hazard ratio = 1.72, 95% confidence intervals: 1.06-2.81; Q2: hazard ratio = 1.64, 95% confidence intervals: 0.99-2.71; Q3: hazard ratio = 1.31, 95% confidence intervals: 0.76-2.25). In the analysis, stratified by sex, there was also significant relationship between IGF-1 and disability among women, but not men. Lower serum IGF-1 was independently related to disability among older adults.