High BMI and the risk of lower extremity fractures in fertile-aged women: A nationwide register-based study in Finland

Abstract

ObjectivesBoth high and low body mass index (BMI) is known to be associated with increased risk for osteoporotic fractures in the postmenopausal population. However, the association between BMI and risk for fracture in the fertile-aged (15–49 years) population is not well studied. We aim to examine how increased BMI affects the risk for fracture leading to hospitalization after delivery in fertile-aged women. Material and methodsIn this nationwide registry-based study, data on all women aged 15–49 years with fractures leading to hospitalization were retrieved from the Care Register for Health Care for the years 2004–2018. The data were linked with data from the National Birth Register, where the BMI status is collected for each pregnancy. Cox regression was used to examine the effect of increased BMI on the risk for fracture within five years after delivery. Risks were analyzed separately for upper extremity, spine and pelvis, and lower extremity fractures. The results were interpreted with hazard ratios (HR), adjusted hazard ratios (aHR), and 95% confidence intervals (CI). ResultsA total of 529 992 pregnant women with 3276 fractures leading to hospitalization within 5-year follow-up were included in this study. Of these, a total of 548 fractures required surgical treatment. Patients with BMI of 30 kg/m2 or more had a higher rate of fractures in the lower extremity (≥50%). In lower extremity fractures, risk for fracture increased with increasing BMI. The risk fracture was highest in the group with BMI of 35–40 kg/m2 (overall lower extremity aHR 2.43 95% CI 1.92–3.06; knee aHR 2.04, 95% CI 1.45–2.87; ankle aHR 3.01, 95% CI 2.16–4.20). ConclusionsHigher BMI was associated to the increased risk for lower extremity fractures, especially ankle fractures, within five years of delivery. Information gained from this study is important in the clinical setting, as patients can be informed of the negative effect of obesity on the post-delivery risk for fractures.