Background&Aim: Fragility fractures, particularly hip fractures, are linked to an increased risk of mortality. This study aimed to test the hypothesis that low bone mineral density (BMD) is associated with a higher risk of post-fracture mortality.
Methods: We utilised prospective data from the Study of Osteoporotic Fractures (SOF) and Osteoporotic Fractures in Men Study (MrOS), which have followed over 11,000 participants aged 65 and older for more than 20 years. A Markov multi-state model was constructed, adjusting for age, BMD, prior fractures, falls, lifestyle factors (smoking, alcohol intake, physical activity), and co-morbidities. This model estimated the 5-year risk of developing osteoporosis (for those without it at baseline), sustaining fractures, and mortality. Gompertz's law of mortality was incorporated to translate these risks into an individual's skeletal age[1], defined as the age of the skeleton resulting from fractures.
Results: Each standard deviation (SD) lower in femoral neck BMD was associated with a 5% increase (95%CI, 0.1%-11%) in mortality risk for non-osteoporotic individuals, a 38% increase (16%-63%) for osteoporotic individuals, and an 11% increase (5%-18%) among those with an existing fracture. Additionally, each SD decrease in femoral neck BMD was linked to a 47% (95%CI, 36%-58%) increase in fracture risk for the non-osteoporosis group and a 75% increase (46%-108%) in the osteoporosis group. The loss of BMD was correlated with an increased skeletal age. For instance, a 70-year-old woman with osteoporosis might have a skeletal age estimated at 72.2 years. The adjusted models with all risk factors provide similar patterns. However, the pattern for males is less pronounced due to fewer transition records.
Conclusions: Low BMD significantly increases the risk of post-fracture mortality in older adults and is associated with an elevated skeletal age. These findings suggest that measures to maintain BMD may help extend life expectancy in older adults with fractures.