Bone strain index may add to fracture risk prediction for postmenopausal women
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Postmenopausal women with higher bone strain index values at the spine, neck and total hip are more likely to have incident fragility fractures vs. those with a lower bone strain index, according to study findings published in Bone.
“Our study is the first evaluating the association of bone strain index at both spine and hip with incident fracture,” Elisabeth Sornay-Rendu, MD, of the French Institute of Health and Medical Research, and colleagues wrote. “We found a greater association with bone strain index values at the spine compared to total hip and femoral neck, especially for vertebral fractures. Furthermore, the cutoff value of 2.1 for spine bone strain index to consider high fracture risk, shows a greater sensitivity and specificity for vertebral fractures than for all fracture prediction and major osteoporotic fractures.”
Research analyzed data from the OFELY study, an ongoing prospective study of bone fragility in women aged 31 to 89 years. Researchers collected data from 846 women who attended a follow-up between 2005 and 2007 and had bone strain index evaluated for the spine, femoral neck and total hip (mean age, 60 years). DXA scans were used to calculate bone strain index and measure areal bone mineral density and trabecular bone score. Femoral neck BMD at baseline was used to calculate Fracture Risk Assessment Tool (FRAX) risk for major osteoporotic fractures. Incident fragility fractures were recorded annually until January 2016.
The study cohort was divided into a premenopausal group (n = 261; mean age, 40 years) and a postmenopausal group (n = 585; mean age, 68 years). For premenopausal women, neck bone strain index (Spearman rank correlation = –0.13; P = .03) and total hip bone strain index (Spearman rank correlation = –0.15; P = .03) were negatively correlated with age. Neck, total hip and spine bone strain index values were positively correlated with BMI (P < .01) and negatively correlated with BMD (P < .0001), neck trabecular bone score (P = .02), hip trabecular bone score (P < .0001) and spine trabecular bone score (P < .0001).
For postmenopausal women, neck and total hip bone strain index were positively correlated with age (P < .0001), and spine bone strain index was positively correlated with BMI (Spearman rank correlation = 0.22; P < .0001). All three bone strain index values were negatively correlated with BMD (P < .0001) and trabecular bone score (P < .0001). Neck and total hip bone strain index were negatively associated with estimated failure load at the distal tibia (P < .0001), and spine bone strain index was negatively associated with estimated failure load at the distal radius (Spearman rank correlation = –0.36; P < .0001).
There were 133 incident fragility fractures reported during a median follow-up of 9.3 years, including 80 major osteoporotic fractures and 53 other types of fractures. After adjusting for age, each standard deviation increase in neck bone strain index (adjusted HR = 1.23; 95% CI, 1.04-1.45; P = .017), total hip bone strain index (aHR = 1.27; 95% CI, 1.08-1.49; P = .004) and spine bone strain index (aHR = 1.35; 95% CI, 1.16-1.57; P < .0001) were associated with an increased risk for all fragility fractures. The associations remained significant for total hip and spine bone strain index after adjusting for FRAX.
After adjusting for age, women had an increased risk for major osteoporotic fractures with each standard deviation increase in neck bone strain index (aHR = 1.3; 95% CI, 1.06-1.6; P = .011), total hip bone strain index (aHR = 1.3; 95% CI, 1.07-1.57; P = .008) and spine bone strain index (aHR = 1.35; 95% CI, 1.11-1.64; P = .003). All three associations remained significant after adjusting for FRAX.
“The added value of bone strain index should be more investigated in further studies, but our results reinforce the idea that other determinants of bone strength besides areal BMD should be used in clinical practice for fracture prediction,” the researchers wrote.
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