Republic of Korea: Female reproductive factors are independently associated with fracture risk in postmenopausal women, finds a recent study in the journal JAMA Network Open. For instance, a shorter lifetime exposure to endogenous estrogen is associated with a higher fracture risk.
The findings suggest the need for interventions to reduce fracture risk in women at high risk, including those without osteoporosis.
Previous studies have suggested estrogen level to be positively associated with bone mineral density (BMD) but data on fracture risk after menopause is limited. To fill this knowledge gap, Jung Eun Yoo, Seoul National University Hospital, Seoul, Republic of Korea, and colleagues aimed to investigate whether female reproductive factors are associated with fractures among postmenopausal women.
For the purpose, the researchers used data from the Korean National Health Insurance Service database on 1 272 115 postmenopausal women. The women did not have any previous fracture and underwent both cardiovascular and breast and/or cervical cancer screening from January 1 to December 31, 2009. The researchers extracted information about reproductive factors (age at menarche, age at menopause, parity, breastfeeding, and exogenous hormone use) by self-administered questionnaire.
The main outcomes was incidence of any fractures and site-specific fractures (vertebral, hip, and others).
Key findings of the study include:
Compared with earlier age at menarche (≤12 years), later age at menarche (≥17 years) was associated with a higher risk of any fracture (adjusted hazard ratio [aHR], 1.24) and vertebral fracture (aHR, 1.42).
Compared with earlier age at menopause (<40 years), later age at menopause (≥55 years) was associated with a lower risk of any fracture (aHR, 0.89), vertebral fracture (aHR, 0.77), and hip fracture (aHR, 0.88).
Longer reproductive span (≥40 years) was associated with lower risk of fractures compared with shorter reproductive span (<30 years) (any fracture: aHR, 0.86; vertebral fracture: aHR, 0.73; and hip fracture: aHR, 0.87).
Parous women had a lower risk of any fracture than nulliparous women (aHR, 0.96).
Although breastfeeding for 12 months or longer was associated with a higher risk of any fractures (aHR, 1.05) and vertebral fractures (aHR, 1.22), it was associated with a lower risk of hip fracture (aHR, 0.84).
Hormone therapy for 5 years or longer was associated with lower risk of any factures (aHR, 0.85), while use of oral contraceptives for 1 year or longer was associated with a higher risk of any fractures (aHR, 1.03).
"The findings of this cohort study suggest that female reproductive factors are independent risk factors for fracture, with a higher risk associated with shorter lifetime endogenous estrogen exposure," wrote the authors.
The study, "Association of Female Reproductive Factors With Incidence of Fracture Among Postmenopausal Women in Korea," is published in the journal JAMA Network Open.
DOI: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774642