Objective: To analyze the association between hip fracture incidence in 12 regional blocks within Japan and dietary intake of four key nutrients: calcium, magnesium, vitamin D, and vitamin K.
Design: An ecological study.
Methods: Using data from the 2002 national survey on the incidence of hip fracture and the National Nutritional Survey of Japan, a standardized incidence ratio of hip fracture was calculated, and the association between the standardized incidence ratio and each nutritional intake was assessed for each region using Pearson's correlation coefficient and partial correlation analysis.
Results: There were significant correlations between the standardized incidence ratio by region and magnesium, vitamin D, and vitamin K in both men and women, and calcium in women. The strongest inverse correlations were found in vitamin K in both men and women (r = -0.844, P = 0.001, and r = -0.834, P = 0.001, respectively). After adjusting for calcium, magnesium, and vitamin D, the partial correlation between the standardized incidence ratio by regional block and vitamin K was strongest in both men and women (partial correlation coefficient, pcc = -0.673, P = 0.04; pcc = -0.575, P = 0.106, respectively).
Conclusions: The significant correlation between hip fracture incidence and vitamin K intake, and also regional variations in food patterns, suggest that increasing intake of vegetables and legumes might lead to a decrease in hip fracture incidence in the future. Further, this study suggests that a review of the dietary reference value of vitamin K from the perspective of osteoporosis would be useful.