Lifetime Exposure to Occupational Physical Demand and Hip Fractures in Post-menopausal Women

INTRODUCTION: Bone fractures are a leading cause of disability, morbidity, and mortality and disproportionately affect older women. It is hypothesized that occupational physical demand may reduce fracture risk via maintenance of mobility, physical functioning, muscle strength and balance although few studies have examined women’s occupational exposure throughout the life course.

METHODS: Data from the Women’s Health Initiative Observational Study (n=84,517), a long-term national cohort of women aged 50-79, were used to examine the association between physical demand in jobs outside the home, before and after menopause, and risk of hip fracture. At study baseline, women reported description of major jobs held since 18 years of age (including age began and duration of employment), which were coded using the 2010 Standard Occupational Classification (SOC). Women were classified with regard to average intensity of physical demand and duration of exposure for the periods before and after menopause using data derived from the Occupational Information Network (O-Net) for each SOC code. Annual self-report of hip fracture during study follow-up was centrally adjudicated by medical record review; the overall rate of hip fracture during follow-up was 2.3%. Poisson regression was used to estimate associations between physical demand and hip fracture.

RESULTS: A10-point increase in the intensity of physical demand during the post-menopausal period was not associated with risk of hip fracture (relative risk: 1.07, 95% confidence interval 1.00 - 1.13) after adjustment for age at study entry, ethnicity, birth region and parental history of hip fracture. We also did not observe an association between pre-menopausal occupation and hip fracture in later life.

CONCLUSIONS: These results suggest that occupational physical demand does not protect against hip fractures later in life.