Background: Osteoporosis affects approximately one in five European women and leads to fragility fractures, which result in poor health, social and economic consequences. Fragility fractures are a strong risk factor for subsequent major osteoporotic fracture (MOF), with risk of MOF being elevated in the 1–2 years following an earlier fracture, a concept described as “imminent risk”. This study examines risk of subsequent MOF in patients with one, two or three prior fractures by age and type of fracture.
Methods: In this retrospective, observational cohort study, Swedish women aged ≥50 years with ≥1 any clinical fragility fracture between July 1, 2006 and December 31, 2012 were identified from Sweden's National Patient Register. Each patient was age- and sex-matched to three controls without history of fracture. Group 1 women included those with one fragility fracture during the study period; Group 2 included those with two fragility fractures; and Group 3 included those with three fragility fractures. “Index fracture” was defined as the first fracture during the study period for Group 1; the second for Group 2; and the third for Group 3. Patients in each cohort and matched controls were followed for up to 60 months or until subsequent MOF (hip, vertebra, forearm, humerus), death or end of data availability.
Results: 231,769 women with at least one fracture were included in the study and therefore constituted Group 1; of these, 39,524 constituted Group 2 and of those, 7656 constituted Group 3. At five years, cumulative incidence of subsequent MOF was higher in patients with a history of fracture as compared to controls (Group 1: 20.7% vs 12.3%; Group 2: 32.0% vs 15.3%). Three-year cumulative incidence for Group 3 was 12.1% (vs 10.7% for controls). After adjusting for baseline covariates, risk of subsequent MOF was highest within 0–24 months following an index fracture, then decreased but remained elevated as compared to controls. Having two prior fractures, vertebral fractures and younger age at time of index fracture were associated with greater relative risk.
Conclusions: Women with a history of osteoporotic fracture are at increased risk of subsequent fracture, which is highest during the first 24 months following a fracture. Younger women and those with vertebral fractures are at greatest relative risk, suggesting that treatment should target these patients and be timely enough to impact the period of imminent risk.