Vitamin D sufficiency is associated with low incidence of limb and vertebral fractures in community-dwelling elderly Japanese women: the Muramatsu Study

Abstract

Data on the association between vitamin D status and osteoporotic fracture in Asians are sparse. We conducted a 6-year cohort study of 773 community-dwelling elderly Japanese women and found that serum 25-hydroxyvitamin D (25(OH)D) ≥ 71nmol/L was associated with a reduced risk of osteoporotic limb and vertebral fractures. Data on the association between vitamin D status and osteoporotic fracture in Asians are sparse. This study aimed to clarify the association between vitamin D and other markers of nutritional status with the incidence of fracture in elderly Japanese women. We conducted a cohort study with a 6-year follow-up of 773 community-dwelling women aged 69years and older. The 6-year follow-up ended in 2009. We assessed serum 25-hydroxyvitamin D, undercarboxylated osteocalcin (an index of vitamin K status), and calcium intake. The primary outcome was incident limb and vertebral fractures. Covariates were forearm bone mineral density (BMD), age, body mass index, osteoporosis treatment, and physical activity. The mean serum 25(OH)D concentration was 60.0nmol/L. Thirty-seven limb fractures and 14 vertebral fractures occurred in 4,392 person-years. Lower forearm BMD was significantly associated with increased incident fracture (P = 0.0242). The adjusted hazard ratios (HR) of fracture for the first quartile (<47.7nmol/L) and the third quartile (59.2-70.9nmol/L) of serum 25(OH)D, compared to the fourth quartile (≥71.0nmol/L), were 2.82 (95% confidence interval (CI), 1.09-7.34) and 2.82 (95%CI, 1.09-7.27), respectively. The pooled adjusted HR was 0.42 (95%CI, 0.18-0.99) when the incidence in the fourth quartile (≥71.0nmol/L) was compared to the other three quartiles combined (<71.0nmol/L). Vitamin K status and calcium intake were not associated with incident fracture. Sufficient vitamin D status, i.e., serum 25(OH)D ≥ 71nmol/L, is associated with low limb and vertebral fracture risk in community-dwelling elderly women.