Objectives: The decline in the growth hormone/insulin-like growth factor-I (GH/IGF-I) axis during normal aging might be involved in the changes in body composition associated with increasing age. We conducted a study to investigate serum IGF-I levels across different age categories and a possible association between serum IGF-I and measurements of body composition in older people.
Design: A cross-sectional analysis of community dwelling older people, which participated in a large longitudinal cohort study (Longitudinal Aging Study Amsterdam).
Subjects: 1319 subjects, 644 men, mean age 75.6 +/- 6.6 years and 675 women, mean age 75.4 +/- 6.6 years.
Main outcome measurements: IGF-I, body mass index (BMI), waist, waist-hip ratio (WHR), fat mass, lean body mass and total bone mineral density.
Results: IGF-I levels were significantly lower in the highest age categories. BMI and biceps skinfold measurements were lower in the lowest IGF-I quartile in men aged > or =75.5 years. In men with a low total physical activity score (<131 min/day), BMI, WHR and skinfolds were significantly lower in the lowest IGF-I quartile. In women with a high total physical activity score (>174 min/day), WHR was lower in the lowest IGF-I quartiles.
Conclusion: In this large cohort of community dwelling older people, we observed lower serum IGF-I levels in the higher age categories. A low serum IGF-I was associated with significantly lower measurements of body composition, such as BMI, skinfolds and WHR. These results do not support previous findings that high IGF-I levels are favourable for a healthy body composition in community dwelling older people.