Influence of Obesity on Vertebral Fracture Prevalence and Vitamin D Status in Postmenopausal Women

A. El Maghraoui; S. Sadni; A. El Maataoui; A. Majjad; A. Rezqi; Z. Ouzzif; A. Mounach

Disclosures

Nutr Metab. 2015;12(44) 

In This Article

Background

Patients with osteoporosis are at increased risk for fractures especially vertebral, wrist, and hip fractures.[1] Vertebral fractures (VFs) can easily go undiagnosed as they are clinically silent in two third of the cases. Moreover, even when they are asymptomatic, they are associated with reduced quality of life, increased morbidity and mortality, and increased risk of future vertebral and non-VFs.[2,3] Several studies showed that weight is an important determinant of bone health. In early adulthood, weight may determine peak bone mass, and persons who are overweight in young age may be at an advantage regarding bone mass in older age. Thus, whereas obesity is associated with increased mortality and morbidity from diabetes and cardiovascular diseases, high body weight is widely believed to be protective against the development of osteoporosis and fracture risk. The fracture assessment tool FRAX, which includes BMI was developed based on a meta-analysis of 12 cohorts, which showed a negative correlation between BMI and incident hip, osteoporotic, and all fractures, when the models did not include BMD. This finding has been recently confirmed by the Million Women Study,[4] a large-scale observational study which found that women with higher BMI have not only increased BMD but also robust femur geometry assessed by hip structure analysis. The negative BMI–fracture association was specific to hip and central body fractures.[5] However, the effect of BMI on fracture at a given level of BMD remains controversial, partly because of its differential effects on different fracture sites. It has been suggested that increased BMI was a protective factor of hip fracture while obesity was a risk factor of ankle and upper leg fractures. Confirmation that obesity was not a protective factor against low trauma fractures was reported in 2011, when the Global Study of Osteoporosis in Women (GLOW), a multicentre prospective observational study conducted in 60,393 postmenopausal women, showed a comparable prevalence and incidence of fractures in normal weight and obese women.[6]

The prevalence and clinical risk factors associated with VFs have been well studied in women.[7–10] A negative effect of BMI on VFs was found in a pan-European study in which the prevalence of vertebral deformity in a given country was inversely related to the mean BMI in the study population in that country (r = −0.66).[11] However, Pirro et al. showed that an association between BMI and a higher likelihood of having a VF, irrespective of the positive association between BMI and BMD.[12] We showed in a previous study that VFs prevalence was associated to vitamin D deficiency in a cohort of post menopausal women.[13] On the other hand, vitamin D deficiency has been associated with obesity irrespective of age, latitude, cut-offs to define vitamin D deficiency and the Human Development Index of the study location.[14–17] Thus, we aimed in the present study to evaluate the effect of BMI on vitamin D status and on densitometric vertebral VFs in a large series of asymptomatic women aged over 50 who had a VFA examination during their bone mineral density (BMD) testing.

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