A Svedbom

Reversal in the secular trend of hip fracture incidences in Austria.

Sir, In their recently published article, Mann et al. state that they have found no levelling-off or downward trend in hip fracture incidences in the Austrian population ≥50 years of age [1]. However, in this otherwise excellently written manuscript, Mann et al. are referring to data that was published in 2008 [2]. Th ese data were based on hip fracture incidences obtained over a period of 13 years, that is from 1994 to 2006. Considering these data, the authors concluded that in contrast to fi ndings in other countries there is no levelling-off or downward trend of hip fracture incidence in the Austrian elderly population. However, the data Mann et al. are referring to, no longer refl ect the current knowledge on hip fracture incidences in Austria. Furthermore, the methodology that has been used in the study mentioned has several limitations [2]. First, the number of hip fractures has been derived from the Austrian Hospital Discharge Register (AHDR) without having considered a correction factor for multiple registrations for the same diagnosis. Second, the time period under consideration has been relatively short. Th ird, the measures of change used, i.e. average annual changes (incidence rate ratios = IRRs), were calculated from the data for the entire period, making the analysis susceptible to large changes in any given time period. Th e use of the analysis to make inferences about changes in trend is thus potentially limited. In addition, in the solely online available Appendix to their manuscript (http://www.biomedcentral.com/content/supplementary/1471-2318-8-35-S1. doc), Mann et al. have shown that the age-standardized incidence (fractures per 100,000 person years) in women increased from 557 in 1994 to 630 in 1999, and fl uctuated between 613 and 643 thereafter, with the last observation (2006) at 623, indicating that this may be a problem, potentially invalidating their conclusion of no levelling-off or downward trend in hip fracture incidence in the Austrian elderly population. We have recently published hip fracture incidences in the Austrian population using data extracted from the AHDR over a period from 1989 to 2008, i.e. over a period of twenty years [3]. A correction factor of 0.9 for multiple registrations of the same diagnosis was determined by de-anonymizing aggregated data from two large Austrian centres for trauma surgery, which cover almost 6% of all hip fractures admitted to hospitals in Austria within a year. Th e age-standardized incidence in women increased until 2005, from 493 to 642, and decreased thereafter. In men, it increased until 2006, from 192 to 280, and decreased thereafter with a slight rebound in 2008. Th e age-standardized incidence in the entire population increased until 2005, from 376 to 496, and decreased thereafter (Fig. 1). Th e IRR for the years 2006–2008 was signifi cantly below the IRR for the years 1989–2005 (0.94, p < 0.01), driven by a lower IRR in women (0.91, p < 0.01) and to a lesser extent by a lower IRR (p = n.s.) in men (0.96, p < 0.15). Overall, our study clearly indicates that since 2006, agestandardized incidence of hip fractures has been declining in the Austrian population aged 50 years and above, and that this reversal in the secular trend has primarily been driven by a decrease in hip fracture incidence in women. Despite the fact that the global hip fracture incidence has been projected to increase dramatically during the next few decades due to the increasing number of elderly people [4], decreases in hip fracture incidence have been observed in several populations of the so-called Western World [3]. Several reasons have been put forward to explain this reversal in the secular trend, amongst which are increases in the average body mass index in elderly people, eff ects of interventional programmes to reduce the risk of falls, or changes in early-life risk factors such as perinatal nutrition [3]. However, since none of the hypothetical reasons considered has been supported by strong evidence so far, there is a clear need for large prospective