ABSTRACT. Objective: To examine the association of serum concentrations of 25-hydroxyvitamin D (25(OH)D), interleukin-6 (IL-6), C-reactive protein (CRP), and insulin-like growth factor-1 (IGF-1) with prevalent and incident frailty. Design: The Longitudinal Aging Study Amsterdam, a prospective cohort study with three-yearly measurement cycles. Setting: General population-based sample. Participants: The respondents were men and women aged 65 and over, who participated at T1 (1995/1996, N=1,720) and T2 (1998/1999, N=1,509). Blood samples were obtained at T1 (N=1,271). Measurements: The presence of frailty at T1 and 3-year incidence of frailty. Frailty is defined as the presence of three out of nine frailty indicators. Results: At T1, 242 (19.0%) of all respondents were frail. Those who were frail at T1 had higher CRP and lower 25(OH)D levels. Serum 25(OH)D remained associated with frailty after adjustment for potential confounders with odds ratios of 2.60 (95%CI 1.60-4.21) for 25(OH)D< 25nmol/l and 1.72 (95%CI 1.19-2.47) for 25(OH)D 25-50 nmol/l versus high levels of 25 (OH)D. Of the non-frail at T1, 125 respondents (14.1%) became frail at T2. After adjustment, moderately elevated CRP levels (3-10 ug/ml) (OR 1.69, 95%CI 1.09-2.63) and low 25(OH)D (OR 2.04, 95%CI 1.01-4.13) were associated with incident frailty. No consistent associations were observed for IL-6 and IGF-1. Conclusion: Low 25(OH)D levels were strongly associated with prevalent and incident frailty; moderately elevated levels of CRP were associated with incident frailty.
