Potential Impact of Osteoporosis Treatment on Hip Fracture Trends

The efficacy of osteoporosis treatment with antiresorptive agents has been shown in a number of large and welldesigned clinical trials, but the effectiveness of these interventions to reduce the burden of fractures in the general population is less certain. Various studies have shown that relatively few people are screened for osteoporosis and that many of those who are evaluated subsequently discontinue treatment after only a few months. Moreover, the majority of patients who sustain an osteoporotic fracture are not treated at all, even though they are at greatly increased risk of another one. In this context, Jaglal et al., in this issue of the Journal, suggest that aggressive diagnosis and treatment of osteoporosis in Canada is having a very substantial effect in lowering the incidence of osteoporotic fractures and that predictions of rising numbers of hip fractures in the future are, therefore, misleading. They base this view on the observation that the estimated ageadjusted incidence of hip fractures in Canadian women residing in Ontario fell by about 20% between 1992 and 2005, with a similar decline in men, while wrist fracture incidence decreased by a lesser amount. These changes were attributed to a marked concurrent increase in the number of people filling at least one prescription for an antiresorptive agent (mostly etidronate, but excluding hormone therapy), from about 13,000 in 1996 to nearly 226,000 in 2003. This, in turn, was presumably in response to a 10-fold increase in BMD testing from about 37,000 DXA tests in 1992 to just over 404,000 in 2001. On the basis of these trends, the authors conclude that greater diagnosis and treatment of osteoporosis has reduced the number of hip fractures below previously projected figures, even in the face of an increased number of elderly Canadians. These results are promising, and they raise two main questions. First, do these data prove that the hip fracture projections were “wrong,” as indicated in the title of their paper? Second, are the reported trends in BMD testing and prescribing antiresorptives the cause of the fracture reduction that was seen? On reflection, it should be clear that hip fracture projections do not represent a prophecy but rather a warning of what could happen later unless more serious attempts are made to control the main determinants of hip fracture risk (i.e., skeletal fragility and falls). Because comprehensive interventions to prevent falls are challenging and of somewhat limited effectiveness, the focus of most fracture prophylaxis schemes centers on preventing bone loss. Indeed, when taken at face value, the results of Jaglal et al. show the value of the hip fracture projections that were made earlier for the Canadian population (i.e., they stimulated a greater effort to manage osteoporosis, and the burden of hip fractures was reduced as a consequence). It does not necessarily follow, however, that this is a generalizable result. Previously published hip fracture projections were based on clearly stated assumptions about secular trends in fracture incidence, combined with estimates of future population growth. Because hip fracture rates rise exponentially with age, it is growth in the elderly population that is most germane. In the United States in the 14 years between 1992 and 2005, the period covered by Jaglal et al., the population 65 years of age grew by about 14%; however, it is projected to increase by 44% in the next 14-year period (2006–2019), as the wave of post–World War II “baby boomers” moves into this age group. Even larger increases are expected in Canada, where the number of men and women 65 years of age is projected to increase by 62% and 51%, respectively, between 2005 and 2020. These projections are robust because all individuals who will be 65 years of age in 2020 have already been born. Thus, the benefits of reduced hip fracture rates could yet be overwhelmed by a larger number of elderly residents. In other parts of the world, this is virtually guaranteed to be so. The population 65 years of age in Asia, for example, is expected to increase 2.3-fold, from 921 million to 2.2 billion, between 1990 and 2025. Moreover, there is no indication that the use of effective osteoporosis interventions is increasing dramatically in those regions where growth in the elderly population is most rapid. The second important question is whether the decrease in fracture incidence can be shown to be caused by the osteoporosis interventions described. This is problematic for two reasons that relate to the pattern of secular trends and the performance characteristics of BMD tests. First, the The authors have no conflict of interest.