Smoking is associated with an increased risk for fractures in women after childbirth: a nationwide population-based cohort study in Finland

Matias Vaajala; Ilari Kuitunen; Lauri Nyrhi; Ville Ponkilainen; Tuomas T Huttunen; Ville M Mattila

doi:10.2340/17453674.2022.5275

Authors

Matias Vaajala Faculty of Medicine and Life Sciences, University of Tampere, Tampere
Ilari Kuitunen Department of Pediatrics, Mikkeli Central Hospital, Mikkeli; Institute of Clinical Medicine and Department of Pediatrics, University of Eastern Finland, Kuopio https://orcid.org/0000-0001-8178-9610
Lauri Nyrhi Faculty of Medicine and Life Sciences, University of Tampere, Tampere; Department of Surgery, Central Finland Central Hospital Nova, Jyväskylä https://orcid.org/0000-0001-6291-4869
Ville Ponkilainen Department of Surgery, Central Finland Central Hospital Nova, Jyväskylä https://orcid.org/0000-0002-5026-4560
Tuomas T Huttunen Faculty of Medicine and Life Sciences, University of Tampere, Tampere; Department of Anesthesia and Intensive Care, Tampere Heart Hospital, Tampere University Hospital, Tampere https://orcid.org/0000-0001-7884-7533
Ville M Mattila Faculty of Medicine and Life Sciences, University of Tampere, Tampere; Department of Orthopaedics and Traumatology, Tampere University Hospital, Tampere, Finland https://orcid.org/0000-0001-9946-4830

DOI:

https://doi.org/10.2340/17453674.2022.5275

Keywords:

Epidemiology, Fractures, Osteoporosis, Smoking

Abstract

Background and purpose: Smoking weakens bone health and increases the risk of fractures. We investigated the incidence of fractures in smoking, fertile-aged women and compared it with that of non-smoking, fertile-aged women using data from nationwide registers.
Patients and methods: We conducted a retrospective register-based nationwide cohort study from 1998 to 2018. We identified all women smoking during pregnancy from the Medical Birth Register and compared these with non-smokers. We gathered fractures for both groups from the Care Register for Health Care. Pregnancies with missing smoking or socioeconomic status were excluded. A Cox regression model was used to analyze adjusted hazard ratios (aHR) with 95% confidence intervals (CI) for fractures during the 5-year follow-up starting from delivery. The model was adjusted for the age of the mother at the time of delivery and socioeconomic status.
Results: The smoking group included 110,675 pregnancies and the non-smoking group 628,085 pregnancies. The overall fracture rate was higher in smokers after 1-year follow-up (aHR 1.7, CI 1.5–2.0) and 5-year follow-up (aHR 1.7, CI 1.6–1.8). After 5-year follow-up, the fracture rates for polytraumas (aHR 2.3, CI 1.4–3.7), inpatient admitted fractures (aHR 2.0, CI 1.7–2.4), and non-admitted fractures (aHR 1.8, CI 1.7–1.9) were all higher among smoking women.
Conclusion: Smoking in fertile-aged women was associated with a higher risk of fractures during the 1-year and 5-year follow-up after giving birth, also after adjusting for age and socioeconomic status. Whether the increased fracture risk is caused by direct effects of smoking on bone health or riskier behavior remains uncertain.