FRAX scores which include BMD as a factor in calculations may not be accurate for estimating fractures in women with diabetes, a Victorian study shows.
Baseline data from 566 women in the Geelong Osteoporosis Study was used to calculate FRAX scores, with and without BMD.
The predicted number of major osteoporotic fractures (MOF) and hip fractures over the following 10 years were compared to the observed number of fractures in the cohort.
The women were aged between 40 and 90 years at baseline. About 44% were normoglycaemic, a similar number had impaired fasting glucose (IFG) and 12% had diabetes.
When BMD was not included, women with diabetes tended to have a higher FRAX score for both MOF and hip fractures (7.1 and 2.5) compared with women who had normoglycaemia (4.3 and 1.2) or IFG (5.1 and 1.3).
When BMD was included, there was no difference (5.3 and 1.0 for women with diabetes; 3.7 and 0.6 for normoglycaemic women; 4.3 and 0.8 for women with IFD).
“This study shows that FRAX without BMD tended to be different between the glycaemia groups, while the addition of BMD attenuated the observed inter-group differences in FRAX scores,” the study authors said.
Professor Julie Pasco, head of the Epi-Centre for Healthy Ageing at Barwon Health, told the limbic the increased bone fragility in people with diabetes was not picked up with bone densitometry.
“It is recognised that fracture risk is greater for people with diabetes than people without diabetes even though the BMD is not low – it is either normal or elevated.”
She said some of the suggested mechanisms through which diabetes impacted bone were a direct effect of hyperglycaemia, accumulation of advanced glycation end products, a decrease in insulin and insulin-like growth factors, and lower rates of bone turnover.
“There is also the problem with people with diabetes that they might have a higher rate of falls too.”
“What hasn’t been looked at very much is the position of the impaired fasting glucose group, which was investigated in this analysis as well,” she said.
However the study found that the impact of IFG on fracture risk was still unclear.
“Arising from this work, we are suggesting clinicians should calculate FRAX without BMD for people with diabetes,” said Professor Pasco.
“When you calculate FRAX with the BMD score, the BMD dominates. If you leave the BMD out, the other clinical risk factors become more prominent in the calculation of fracture risk.”
She said other groups have looked at ways of tweaking FRAX calculations to adjust for diseases such as diabetes but there was no consensus as yet.
“The main point of this paper is to suggest use of FRAX without BMD.”
She said data from male participants in the Geelong Osteoporosis Study would take longer to mature as there were fewer fractures in men.
However given that the fracture risk is greater in men and women in the presence of diabetes, it was possible the findings would be similar.