Impact of Hip Fracture on Mortality: A Cohort Study in Hip Fracture Discordant Identical Twins

Authors

  • Karl Michaëlsson,

    Corresponding author
    1. Department of Surgical Sciences, Section of Orthopaedics, Uppsala University, Uppsala, Sweden
    2. Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
    • Address correspondence to: Karl Michaëlsson, MD, PhD, Department of Surgical Sciences and Uppsala Clinical Research Center, Uppsala University, SE-751 85 Uppsala, Sweden. E-mail: karl.michaelsson@surgsci.uu.se

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  • Peter Nordström,

    1. Department of Community Medicine and Rehabilitation, Section of Geriatric Medicine, Umeå University, Umeå, Sweden
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  • Anna Nordström,

    1. Department of Community Medicine and Rehabilitation, Section of Rehabilitation Medicine, Umeå University, Umeå, Sweden
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  • Hans Garmo,

    1. Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
    2. King's College, London, School of Medicine, Division of Cancer Studies, London, UK
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  • Liisa Byberg,

    1. Department of Surgical Sciences, Section of Orthopaedics, Uppsala University, Uppsala, Sweden
    2. Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
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  • Nancy L Pedersen,

    1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
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  • Håkan Melhus

    1. Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
    2. Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
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ABSTRACT

Several studies have shown a long-lasting higher mortality after hip fracture, but the reasons for the excess risk are not well understood. We aimed to determine whether a higher mortality after hip fracture exists when controlling for genetic constitution, shared environment, comorbidity, and lifestyle by use of a nationwide cohort study in hip fracture discordant monozygotic twins. All 286 identical Swedish twin pairs discordant for hip fracture (1972 to 2010) were identified. Comorbidity and lifestyle information was retrieved by registers and questionnaire information. We used intrapair Cox regression to compute multivariable-adjusted hazard ratios (HRs) for death. During follow-up, 143 twins with a hip fracture died (50%) compared with 101 twins (35%) without a hip fracture. Through the first year after hip fracture, the rate of death increased fourfold in women (HR = 3.71; 95% confidence interval [CI] 1.32–10.40) and sevenfold in men (HR = 6.67; 95% CI 1.47–30.13). The increased rate in women only persisted during the first year after hip fracture (HR after 1 year = 0.99; 95% CI 0.66–1.50), whereas the corresponding HR in men was 2.58 (95% CI 1.02–6.62). The higher risk in men after the hip fracture event was successively attenuated during follow-up. After 5 years, the hazard ratio in men with a hip fracture was 1.19 (95% CI 0.29–4.90). On average, the hip fracture contributed to 0.9 years of life lost in women (95% CI 0.06–1.7) and 2.7 years in men (95% CI 1.7–3.7). The potential years of life lost associated with the hip fracture was especially pronounced in older men (>75 years), with an average loss of 47% (95% CI 31–61) of the expected remaining lifetime. We conclude that both women and men display a higher mortality after hip fracture independent of genes, comorbidity, and lifestyle. © 2014 American Society for Bone and Mineral Research.

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