Hip fractures have steadily declined in the USA. We found that bone health, as measured by bone mineral density, has significantly improved over the past 30 years. Our findings contradict previous studies and offer one explanation for the decline in hip fractures.
Purpose: Despite the widespread undertreatment of osteoporosis, hip fractures have been declining in the USA. The reasons for this decline are unclear; however, one possible explanation could be that the bone health has improved over time.
Methods: To determine the trends in bone density in the USA, we analyzed the bone mineral density scans of 7216 subjects across three generations in the Framingham Heart Study. We compared the mean femoral bone mineral density (BMD) between cohorts then constructed a linear regression model controlling for age, sex, BMI, and smoking rates.
Results: We observed that the mean BMD of each successive Framingham cohort increased (p < 0.001). After controlling for age, subjects born later had higher BMD. The results from the linear-regression model developed on the original cohort indicated that the BMD of the women from the offspring and third generation were higher than what would be predicted. Younger generations demonstrated higher activity scores (p < 0.001), and lower smoking rates (p = 0.045).
Conclusion: These data suggest that bone health, measured by bone mineral density scans, is improving in later generations, in part due to decreased smoking rates and higher rates of activity.
Keywords: Bone mineral density; Cohort study; DXA; Exercise; Hip fracture prevention.
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