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 IGF‐1, 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‐trend_T1‐T3<.01) and slower walking speed (P‐trend_T1‐T3=.03), lower IGF‐1 had a borderline significant association with worse handgrip strength (P‐trend_T1‐T3=.06), and better grip strength was observed in the middle IGFBP‐3 tertile than in the low or high tertiles (P=.03). Adjusted for age, sex, and race, high IGFBP‐1 predicted greater mortality (P‐trend_T1‐T3<.001, hazard ratio (HR)_T3vsT1=1.48, 95% confidence interval (CI)=1.15–1.90); this association was borderline significant after additional confounder adjustment (P‐trend_T1‐T3=.05, HR_T3vsT1=1.35, 95% CI=0.98–1.87). High IGFBP‐1 was associated with greater risk of incident ADL difficulties after adjustment for age, sex, race, and other confounders (P‐trend_T1‐T3=.04, HR_T3vsT1=1.40, CI=1.01–1.94). Neither IGF‐1 nor IGFBP‐3 level predicted mortality or incident ADL difficulties. CONCLUSION: In adults aged 65 and older, high IGFBP‐1 levels were associated with greater risk of mortality and poorer functional ability, whereas IGF‐1 and IGFBP‐3 had little association with these outcomes.