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Secular Trends in Swedish Hip Fractures 19872002: Birth Cohort and Period Effects

Rosengren, Björn E.a,b; Ahlborg, Henrik G.a,b; Mellström, Danc,d; Nilsson, Jan-Åkea,b; Björk, Jonase; Karlsson, Magnus K.a,b

doi: 10.1097/EDE.0b013e318256982a
Injury

Background: Recently, a leveling off in hip-fracture incidence has been reported in several settings, but the annual number is nonetheless predicted to increase due to the growing elderly population.

Methods: Using Swedish national data for 1987–2002 for all inpatients 50 years or older, we examined the annual number and incidence of hip fractures and explored age, period, and cohort effects. Age adjustment was done by direct standardization, time-trend analysis by linear regression, changes in linear trends by joinpoint regression, and age-period-cohort effects by log-likelihood estimates in Poisson regression models.

Results: Before 1996, the age-standardized hip fracture incidence was stable (0.1% per year [95% confidence interval = −0.2% to 0.5%]), and the annual number of hip fractures increased (2.1% per year [1.8% to 2.4%]). After 1996, both the age-standardized hip fracture incidence (−2.2% per year [−2.8% to −1.6%]) and the number of hip fractures (−0.9% per year [−1.5% to −0.4%]) decreased. The period + cohort effects were more marked among women than men, with a major reduction in hip fracture incidence in subsequent birth cohorts (estimated incidence rate ratio = 2.2 comparing women born 1889–1896 with 1945–1952) or periods (estimated incidence rate ratio = 1.1 comparing women living 1987–1990 with 1999–2002).

Conclusion: The age-standardized hip fracture incidence has decreased since 1996, more than counteracting the effects of the aging population and resulting in a decline in the annual number of hip fractures through 2002. The magnitude of the combined period and cohort effects in women seems to be of biologic importance. If this persists into older age, the annual number of hip fractures will be lower than has been projected.

From the aClinical and Molecular Osteoporosis Research Unit, Department of Clinical Sciences, Lund University, Lund; bDepartment of Orthopaedic Surgery, Skåne University Hospital, Malmö, Sweden; cDepartments of Internal Medicine and dGeriatrics, Center for Bone Research at the Sahlgrenska Academy, the Sahlgrenska Academy at Göteborg University, Göteborg, Sweden; and eCompetence Centre for Clinical Research, Skåne University Hospital, Lund, Sweden.

Submitted 6 April 2011; accepted 24 January 2012; posted 23 April 2012.

Supported by Swedish Research Council (K2007-53X-14080-07-3), Center for Athletic Research 160/07, ALF-research grant 42425, Herman Järnhardt Foundation, and Påhlsson Foundation. The authors reported no other financial interests related to this research.

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Correspondence: Bjorn E. Rosengren, Department of Orthopaedic Surgery, Skåne University Hospital, Malmö, S-205 02 Malmö, Sweden. E-mail bjorn.rosengren@med.lu.se.

© 2012 Lippincott Williams & Wilkins, Inc.