Vitamin D and Hip Fracture Risk

August 19, 2008

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 Vitamin D and Hip Fracture Risk
Background: The relationship between serum 25-hydroxyvitamin D [25(OH) vitamin D] concentration and hip fractures is unclear.

Objective: To see whether low serum 25(OH) vitamin D concentrations are associated with hip fractures in community-dwelling women.

Design: Nested case–control study.

Setting: 40 clinical centers in the United States.

Participants: 400 case-patients with incident hip fracture and 400 control participants matched on the basis of age, race or ethnicity, and date of blood draw. Both groups were selected from 39 795 postmenopausal women who were not using estrogens or other bone-active therapies and who had not had a previous hip fracture.

Measurements: Serum 25(OH) vitamin D was measured and patients were followed for a median of 7.1 years (range, 0.7 to 9.3 years) to assess fractures.

Results: Mean serum 25(OH) vitamin D concentrations were lower in case-patients than in control participants (55.95 nmol/L [SD, 20.28] vs. 59.60 nmol/L [SD, 18.05]; P = 0.007), and lower serum 25(OH) vitamin D concentrations increased hip fracture risk (adjusted odds ratio for each 25-nmol/L decrease, 1.33 [95% CI, 1.06 to 1.68]). Women with the lowest 25(OH) vitamin D concentrations (47.5 nmol/L) had a higher fracture risk than did those with the highest concentrations (70.7 nmol/L) (adjusted odds ratio, 1.71 [CI, 1.05 to 2.79]), and the risk increased statistically significantly across quartiles of serum 25(OH) vitamin D concentration (P for trend = 0.016). This association was independent of number of falls, physical function, frailty, renal function, and sex-steroid hormone levels and seemed to be partially mediated by bone resorption.

Limitations: Few case-patients were nonwhite women. Bone mineral density and parathyroid hormone levels were not accounted for in the analysis.

Conclusion: Low serum 25(OH) vitamin D concentrations are associated with a higher risk for hip fracture.

From press release:

Vitamin D Deficiency Puts Older Women at Risk for Hip Fracture

Previous studies of the effect of low blood vitamin D levels on the risk for hip fractures in older women have given inconsistent results. In this study, researchers took blood to measure vitamin D levels and gathered information about fracture risk from 800 women between the ages of 50 and 79. After following the women for up to nine years, the researchers re-examined them to see who developed hip fractures. The women with hip fractures had lower vitamin D levels – the very lowest of which seemed to increase the risk for hip fractures independently of other factors known to increase hip fracture risk.

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