CLINICAL INVESTIGATIONS Total Insulinlike Growth Factor 1 and Insulinlike Growth Factor Binding Protein Levels, Functional Status, and Mortality in Older Adults

OBJECTIVES: To assess the association between total insulinlike growth factor (IGF)-1, IGF binding protein-1 (IGFBP-1), and IGFBP-3 levels and functioning and mortality in older adults. DESIGN: Cohort study. SETTING/PARTICIPANTS: One thousand one hundred twenty-two individuals aged 65 and older without prior cardiovascular disease events participating in the Cardiovascular Health Study. MEASUREMENTS: Baseline fasting plasma levels of IGF1, IGFBP-1, and IGFBP-3 (defined as tertiles, T1-T3) were examined in relationship to handgrip strength, time to walk 15 feet, development of new difficulties with activities of daily living (ADLs), and mortality. RESULTS: Higher IGFBP-1 predicted worse handgrip strength (P-trendT1-T3o.01) and slower walking speed (P-trendT1-T35 .03), lower IGF-1 had a borderline significant association with worse handgrip strength (P-trendT1T35 .06), and better grip strength was observed in the middle IGFBP-3 tertile than in the low or high tertiles (P5.03). Adjusted for age, sex, and race, high IGFBP-1 predicted greater mortality (P-trendT1-T3o.001, hazard ratio (HR)T3vsT151.48, 95% confidence interval (CI)51.15– 1.90); this association was borderline significant after additional confounder adjustment (P-trendT1-T35 .05, HRT3vsT15 1.35, 95% CI50.98–1.87). High IGFBP-1 was associated with greater risk of incident ADL difficulties after adjustment for age, sex, race, and other confounders (P-trendT1-T35 .04, HRT3vsT151.40, CI51.01– 1.94). Neither IGF-1 nor IGFBP-3 level predicted mortality or incident ADL difficulties. CONCLUSION: In adults aged 65 and older, high IGFBP1 levels were associated with greater risk of mortality and poorer functional ability, whereas IGF-1 and IGFBP-3 had little association with these outcomes. J Am Geriatr Soc 2008.