Low serum levels of 25-hydroxyvitamin D predict hip fracture in the elderly: a NOREPOS study.
J Clin Endocrinol Metab. 2013 Aug;98(8):3341-50. doi: 10.1210/jc.2013-1468.
Holvik K, Ahmed LA, Forsmo S, Gjesdal CG, Grimnes G, Samuelsen SO, Schei B, Blomhoff R, Tell GS, Meyer HE.
Department of Public Health and Primary Health Care, Institute of Medicine, University of Bergen, 5020 Bergen, Norway. kristin.holvik at fhi.no
BACKGROUND: Despite considerable interest, the relationship between circulating 25-hydroxyvitamin D and the risk of hip fracture is not fully established.
OBJECTIVE: The objective of the study was to study the association between serum 25-hydroxyvitamin D concentrations [s-25(OH)D] and the risk of hip fracture in Norway, a high-latitude country that has some of the highest hip fracture rates worldwide.
METHODS: A total of 21 774 men and women aged 65-79 years attended 4 community-based health studies during 1994-2001. Information on subsequent hip fractures was retrieved from electronic hospital discharge registers, with a maximum follow-up of 10.7 years. Using a stratified case-cohort design, s-25(OH)D was determined by HPLC-atmospheric pressure chemical ionization-mass spectrometry in stored serum samples in hip fracture cases (n = 1175; 307 men, 868 women) and in gender-stratified random samples (n = 1438). Cox proportional hazards regression adapted for the case-cohort design was performed.
RESULTS: We observed an inverse association between s-25(OH)D and hip fracture; those with s-25(OH)D in the lowest quartile (<42.2 nmol/L) had a 38% [95% confidence interval (CI) 9-74%] increased risk of hip fracture compared with the highest quartile (≥67.9 nmol/L) in a model accounting for age, gender, study center, and body mass index. The association was stronger in men than in women: hazard ratio 1.65 (95% CI 1.04-2.61) vs hazard ratio 1.25 (95% CI 0.95-1.65).
CONCLUSION: In this prospective case-cohort study of hip fractures, the largest ever reported, we found an increased risk of hip fracture in subjects in the lowest compared with the highest quartile of serum 25-hydroxyvitamin D. In accordance with the findings of previous community-based studies, low vitamin D status was a modest risk factor for hip fracture.