NEW ORLEANS — A femoral neck T score predicts hip fracture risk in women with type 2 diabetes, but the risk is higher for a given T score and age compared with women who do not have diabetes, a multicenter study has shown.
“These findings indicate that bone mineral density T score is useful for clinical evaluation of hip fracture risk in women with type 2 diabetes, but a higher bone mineral density threshold is appropriate for diagnosis of osteoporosis compared with nondiabetic women,” researchers led by Ann V. Schwartz, Ph.D., of the department of epidemiology and biostatistics at the University of California, San Francisco, noted in a poster session at the annual scientific sessions of the American Diabetes Association.
Established methods for predicting fracture from BMD T score and age “may not apply to patients with type 2 diabetes,” the researchers wrote, because older adults with the disease “have increased risk of hip fracture in spite of higher average bone mineral density.”
To compare the fracture risk prediction in older women with and without type 2 diabetes, Dr. Schwartz and her associates used data from the National Institutes of Health-funded Study of Osteoporotic Fractures, a longitudinal cohort trial of white women aged 65 and older at four clinical centers in the United States. At the first follow-up visit, dual-energy x-ray absorptiometry ascertained hip bone mineral density in 7,917 women, including 520 with self-reported type 2 diabetes.
The mean age of those without diabetes was 73 years. Their mean femoral neck score was −1.77, and 563 (7.6%) had more than one hip fracture. The mean age of those with type 2 diabetes was 74 years. Their mean femoral neck score was −1.45, and 47 (9%) had more than one hip fracture.
A Cox regression model that controlled for age and femoral neck T score was used to estimate the 10-year risk of hip fracture, using fractures that occurred after the BMD measurement. This amounted to 68,582 person-years of follow-up.
The researchers found that age-stratified femoral neck T score underestimated the hip fracture risk in women with type 2 diabetes, and determined that the T score should be set 0.6% points higher for women with type 2 diabetes than for their peers who do not have type 2 diabetes.
The study was supported by a research grant from Amgen Inc.