Association Among Serum Insulin-Like Growth Factor-1, Frailty, Muscle Mass, Bone Mineral Density, and Physical Performance Among Community-Dwelling Middle-Aged and Older Adults in Taiwan

Aging is featured by the complex interrelationship among body composition, frailty status, and physical performance. The main aim of this study was to evaluate the association among serum insulin-like growth factor-1 (IGF-1), body composition, and physical function among community-dwelling middle-aged and elderly population in Taiwan. We conducted a cross-sectional study by using the data of I-Lan Longitudinal Aging Study, which recruited a total of 1833 community-dwelling people aged more than 50 years. Data of lean body mass (LBM), appendicular skeletal muscle mass (ASM), total fat mass (TFM), bone mineral density (BMD) of L-spine/hip, handgrip strength, walking speed, International Physical Activity Questionnaire (IPAQ), Charlson comorbidity index (CCI), serum levels of growth hormone, IGF-1, albumin, total cholesterol, triglyceride, blood urea nitrogen, and creatinine were retrieved for analysis. The mean age of participants was 63.9 ± 9.2 years, and 47.5% were men. The serum IGF-1 level was 140.7 ± 57.6 ng/mL in men and 131.4 ± 54.5 ng/mL in women. The estimated rates of IGF-1 decline with age were 1.88 ng/mL·year in men and 2.13 ng/mL·year in women. The prevalence of frailty was 6.8% and that of prefrailty was 40.4%. After adjusting for age, albumin, IPAQ, and CCI in multiple linear regression models, LogIGF-1 was positively correlated with LBM, ASM, ASM index, height, BMD, and handgrip strength, and was inversely correlated with weakness in both genders. In men, the LogIGF-1 level was positively correlated with weight, body mass index (BMI), waist circumference, and TFM. Higher serum IGF-1 was independently associated with more muscle mass, higher BMD, and better handgrip performance in both genders. The positive association of IGF-1 with BMI, weight, TFM, and waist circumference was found in men only. Further longitudinal study to evaluate the effect of serum IGF-1 on frailty incidence is needed for its causal-effect relationship.