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New ‘bone balance index’ identifies women at risk for bone loss
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Researchers have developed an index that aims to predict which women are more likely to experience rapid bone loss during the menopause transition, according to a new study.
The measure, referred to as the “bone balance index” by researchers, appears to reliably predict changes in BMD, making it possible to test the efficacy of interventions to prevent bone loss and maintain bone strength, said Albert Shieh, MD, a fellow in the department of medicine at the University of California, Los Angeles, who helped develop the index.
“Researchers have previously shown that it is difficult to predict an individual’s bone loss by testing the blood or urine for proteins that reflect either bone breakdown or bone formation alone,” Shieh said in a press release. “Since both bone breakdown and bone formation occur at the same time in the body, we created an index that accounts for both processes, and tested whether this new index can help predict bone loss.”
Shieh and colleagues analyzed data from 685 women aged 42 to 52 years who were premenopausal or perimenopausal at baseline participating in the Study of Women’s Health Across the Nation (SWAN), a multicenter, longitudinal study of the menopause transition in a community-based cohort. All women included in the study had their final menstrual period during follow-up. Women provided urine and blood samples to measure serum osteocalcin, urinary N-telopeptide and urinary creatinine and underwent DXA scanning of the lumbar spine and femoral neck at baseline and yearly after.
To create the bone balance index, the researchers estimated the relationship between resorption (urinary N-telopeptide) and formation (osteocalcin) markers when the total formation equaled the total resorption in the cohort with stable BMD (at least 5 years before the final menstrual period), and applied the relationship to measured bone turnover markers in 216 women beginning to lose bone (2 years or less from their final menstrual period). Researchers then annualized percentage declines over the following 3 to 4 years in lumbar spine and femoral neck BMD.
Researchers found that the index was a stronger predictor of bone loss from 2 years before the final menstrual period to 3 to 4 years later vs. measurements of bone breakdown alone. The bone balance index was greater in women with a higher BMI (P = .03), with every 5 kg/m² increment associated with a 0.1 U increase in the standardized bone balance index. The index was lower in women closer to their final menstrual period (P = .007). Each SD decrement in bone balance index was associated with 0.27% yearly decline in lumbar spine BMD (P = .04) and a 38% higher odds of faster lumbar spine bone mass loss (P = .008). Researchers did not find an association between bone balance index and femoral neck BMD; urinary N-telopeptide alone was not associated with either lumber spine BMD or femoral neck BMD.
“This novel approach to assessing an individual’s bone health may help identify which women are at risk of losing vertebral bone mineral density across the menopause transition,” Shieh said. “More studies are needed to test whether this index is useful for predicting bone loss after the menopause transition, and if it is useful for predicting fractures.”
Markers of bone breakdown alone have limited utility in predicting bone loss at an individual level, Shieh said, and better approaches are needed to ensure individuals at highest risk of rapid bone loss are identified quickly. – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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