Original Article
Choice of Lumbar Spine Bone Density Reference Database for Fracture Prediction in Men and Women: A Population-Based Analysis

https://doi.org/10.1016/j.jocd.2013.09.003Get rights and content

Abstract

The diagnosis of osteoporosis in men is controversial, although most studies demonstrate similar fracture rates for men and women with the same level of hip bone mineral density (BMD). Whether this applies to the lumbar spine is currently uncertain and has important implications with respect to choice of reference population for T-score calculation and osteoporosis diagnosis. This question was specifically addressed in the population-based Canadian Multicentre Osteoporosis Study cohort of 4745 women and 1887 men ages 50+ yr at the time of baseline lumbar spine dual energy x-ray absorptiometry. In up to 10 yr of observation, incident clinical major osteoporotic fractures occurred in 110 men (5.8%) vs 543 women (11.4%) (p < 0.001). Mean lumbar spine BMD in men was greater than in women, both among those with and those without incident major osteoporotic fracture (p < 0.001). Men were at slightly lower risk for incident major osteoporotic fracture than women for an equivalent lumbar spine BMD (age- and BMD-adjusted rate ratio 0.75, 95% confidence interval 0.60–0.93, p = 0.008) with similar findings after adjustment for the World Health Organization fracture risk assessment clinical risk factors or competing mortality. No significant sex difference in the BMD relationship was seen for vertebral fractures (clinical or radiographic) or for all fractures. In summary, this large population-based longitudinal cohort study found similar or lower fracture risk for men vs women after adjustment for absolute lumbar spine BMD and additional covariates. The least complicated model for describing fracture risk is therefore to use the same reference lumbar spine data for generating T-scores in men and women.

Introduction

Bone mineral density (BMD) assessment with dual energy x-ray absorptiometry (DXA) is well established in the diagnosis of osteoporosis and for fracture risk assessment in postmenopausal women 1, 2. The diagnosis of osteoporosis in men remains more controversial, and in a review, Khosla et al (3) concluded that the most appropriate definition for osteoporosis in men, in the absence of fractures, was a major unresolved issue and should be the focus of future research.

Since 2001 the International Society for Clinical Densitometry Official Position was to use young female reference data in women and young male reference data in men for T-scores until additional data could clarify the BMD-fracture risk relationship in men (4). Several prospective studies have now shown that men and women with identical hip BMD have the same fracture rates if all other risk factors are the same 5, 6, 7. Therefore, the World Health Organization recently has clarified diagnostic criteria for postmenopausal women by emphasizing a reference site (femoral neck) and reference population (white women ages 20–29 yr based upon the Third National Health and Nutrition Examination Survey) (8).

The 2013 International Society for Clinical Densitometry Position Development Conference, after considering the new data available on the BMD-fracture risk relationship in men, recommended “Use a uniform Caucasian (nonrace adjusted) female reference for men of all ethnic groups” (J. Schousboe, personal communication). This recommendation was assigned a grade of “Fair” based upon the paucity of nonhip BMD data, and most particularly the lack of equivalent lumbar spine data, since this is one of the primary clinical assessment sites for DXA. Therefore, this question was specifically addressed in the population-based Canadian Multicentre Osteoporosis Study (CaMos) cohort, one of the first population-based cohorts to include both men and women.

Section snippets

Study Population

The study sample was selected from participants in an ongoing population-based longitudinal cohort study, the CaMos. We included all CaMos participants ages 50 and over at study entry for whom follow-up data and lumbar spine BMD measurements were available.

The methodological details of CaMos have been described elsewhere (9). In brief, eligible participants were at least 25 yr of age at the start of the study, lived within a 50-km radius of 1 of 9 Canadian cities (St John's, Halifax, Quebec

Results

There were 4745 eligible women and 1887 eligible men who were similar with respect to mean age (women 65.8 yr vs men 65.3 years, p = 0.021). Women had a significantly greater prevalence of previous fracture, parental hip fracture, and rheumatoid arthritis, whereas men had a greater prevalence of current smoking and high alcohol intake (Table 1). As expected, mean lumbar spine BMD was significantly greater in men than women (p < 0.001).

Mean follow-up for men was 8.3 years vs 8.7 years for women (

Discussion

We found that unadjusted risk of incident major osteoporotic fractures were much less in men (approximately half) that in women. As expected, mean lumbar spine BMD was greater in men than women overall and when stratified by fracture status. The finding of greater mean BMD in men with (or without) low-trauma fracture is attributed to the sex-related difference in BMD distribution rather than an intrinsic difference in skeletal fragility. In fact, men were at slightly lower (not higher) major

Acknowledgments

We thank all those participants in CaMos whose careful responses and attendance made this analysis possible. The Canadian Multicentre Osteoporosis Study is supported by Canadian Institutes of Health Research (CIHR), Amgen Canada Inc, Dairy Farmers of Canada, Merck Canada Eli Lilly Canada, and Novartis Canada. Disclosures: William D. Leslie: Speaker bureau: Amgen, Eli Lilly, Novartis. Research grants: Novartis, Amgen, Genzyme. David Goltzman serves as a consultant for Eli Lily, Novartis, Merck,

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