Risk Factors of Osteoporosis: Results of EVOS in Germany

Associations between baseline risk factors and vertebral fracture risk in the Multiple Outcomes of Raloxifene Evaluation (MORE) Study

Different risk factors may influence the effectiveness of osteoporosis therapies. The interaction of 30 baseline risk factors and the effectiveness of raloxifene in the MORE study were assessed. The efficacy of raloxifene in reducing vertebral fractures is largely independent of the presence of clinical risk factors for osteoporotic fractures.

INTRODUCTION

The aim of this analysis was to determine the effect of different risk factors on the effectiveness of raloxifene to reduce vertebral fractures in the Multiple Outcomes of Raloxifene Evaluation (MORE) study using logistic regression models.

MATERIALS AND METHODS

The association was assessed using univariate analyses and a multivariate model between 30 potential risk factors at baseline and the risk of vertebral fractures after 3 years in the placebo group, as well as the interaction of risk factors with raloxifene therapy (at a dose of 60 or 120 mg/day).

RESULTS AND CONCLUSIONS

In the univariate analysis of the placebo group, after adjusting for baseline lumbar spine BMD (LS BMD), short stature (odds ratio [OR] = 1.18), age (OR = 1.38), years since menopause (OR = 1.38), impaired cognitive function, visuospatial capabilities (OR = 1.19), impaired musculoskeletal strength (OR = 1.23), low femoral neck BMD (OR = 1.21), and prior vertebral fracture (OR = 4.95) were significantly associated with the incidence of new vertebral fractures. In the univariate analysis, significant interactions were observed between raloxifene treatment and age (p = 0.04), serum triglycerides (p = 0.03), LS BMD (p = 0.08), and diabetes mellitus (p = 0.04). In the multivariate analysis, the effectiveness of raloxifene was independent of almost all risk factors, with the exception of baseline serum triglyceride level and LS BMD, suggesting an increased efficacy of raloxifene in patients with increased triglyceride levels (p = 0.006) and lower LS BMD values (p = 0.008) at baseline. These data suggest that the efficacy of raloxifene in reducing vertebral fractures is largely independent of the presence of clinical risk factors for osteoporotic fractures.

Epidemiology and outcomes of osteoporotic fractures

Bone mass declines and the risk of fractures increases as people age, especially as women pass through the menopause. Hip fractures, the most serious outcome of osteoporosis, are becoming more frequent than before because the world's population is ageing and because the frequency of hip fractures is increasing by 1-3% per year in most areas of the world. Rates of hip fracture vary more widely from region to region than does the prevalence of vertebral fractures. Low bone density and previous fractures are risk factors for almost all types of fracture, but each type of fracture also has its own unique risk factors. Prevention of fractures with drugs could potentially be as expensive as medical treatment of fractures. Therefore, epidemiological research should be done and used to identify individuals at high-risk of disabling fractures, thereby allowing careful allocation of expensive treatments to individuals most in need.

Secondary osteoporosis and the risk of vertebral deformities in women

Among an age-stratified sample of 942 Rochester, MN women, the overall prevalence of any vertebral deformity, as assessed by radiographic morphometry, was 21.3 per 100. The prevalence increased with age and, after adjusting for age, vertebral deformities were independently associated with height, weight, a history of distal forearm or hip fractures, and anticoagulant use. Altogether, 73% of the women with a vertebral deformity and 66% of controls had one or more of the conditions that have been linked with secondary osteoporosis, which in aggregate were associated with an age-adjusted 1.2-fold (95% CI 0.8-1.7) increase in risk that was not statistically significant. The prevalence of severe vertebral deformities was 11.7 per 100 women and the prevalence of very severe deformities was 5.7 per 100. There was a stronger relationship of age and most other risk factors with severe vertebral deformities than with isolated mild deformities, suggesting that a subset of mild deformities may not represent actual vertebral fractures. The metabolic disorders linked with secondary osteoporosis were associated with little increase in the risk of severe vertebral deformities, taken together, or of mild deformities. However, in aggregate these conditions were associated with a 2.3-fold increase (95% 1.1-4.8) in very severe vertebral deformities, which points to a role for rapid cancellous bone loss among women with the worst spinal osteoporosis.

Epidemiology of spinal osteoporosis

Approximately 30% of postmenopausal white women in the United States have osteoporosis, and 16% have osteoporosis of the lumbar spine in particular. Bone density of the spine is positively associated with greater height and weight, older age at menopause, a history of arthritis, more physical activity, moderate use of alcoholic beverages, diuretic treatment, and current estrogen replacement therapy, whereas later age at menarche and a maternal history of fracture are associated with lower levels of density. Low bone density leads to an increased risk of osteoporotic fractures. Fracture risk also increase with age. Vertebral fractures affect approximately 25% of postmenopausal women, although the exact figure depends on the definition used. Recent data show that vertebral fracture rates are as great in men as in women but, because women live longer, the lifetime risk of a vertebral fracture from age 50 onward is 16% in white women and only 5% in white men. Fracture rates are less in most nonwhite populations, but vertebral fractures are as common in Asian women as in those of European heritage. Other risk factors for vertebral fractures are less clear but include hypogonadism and secondary osteoporosis; obesity is protective of fractures as it is of bone loss. Compared with hip fractures, vertebral fractures are less disabling and less expensive, costing approximately $746 million in the United States in 1995. However, they have a substantial negative impact on the patient's function and quality of life. The adverse effects of osteoporotic fractures are likely to increase in the future with the growing number of elderly people.