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ORLANDO -- Non-vitamin K antagonist oral anticoagulants (NOACs) were associated with fewer adverse bone outcomes compared to warfarin among older patients with atrial fibrillation, a retrospective Taiwanese study found.

In an analysis of more than 17,000 patients, those prescribed NOACs had an adjusted hazard ratio of o.77 (95% CI 0.64-0.92, P=0.004) for developing osteoporosis relative to those on warfarin, reported Huei-Kai Huang, MD, of Buddhist Tzu Chi General Hospital in Hualien, Taiwan.

Moreover, osteoporosis risk continued to decrease with NOACs the longer patients were on them, in a dose-response relationship, he said during a poster presentation at the annual meeting of the .

Compared to warfarin, patients on NOACs also had a lower risk for fractures after taking them from 6 months to a year (aHR 0.70, 95% CI 0.58-0.84, P<0.001) or more than one year (aHR 0.48, 95% CI 0.41-0.57).

But the lower risk for both osteoporosis and fracture wasn't seen with all NOACs. It applied only to patients treated with rivaroxaban (Xarelto) and apixaban (Eliquis), but not dabigatran (Pradaxa).

"If oral anticoagulants are indicated, we suggest rivaroxaban and apixaban may be the better therapeutic choice than warfarin in terms of creating osteoporosis and fracture risk," Huang said. "However, further studies are needed to understand the underlying mechanisms."

These findings align in some respects with a , while deviating in others. That study found lower risk of overall fracture among patients treated with NOACs compared to warfarin -- mainly driven by older patients on long-term anticoagulants -- but not for fractures involving the hip or femoral neck.

However, in the Taiwanese study, patients on NOACs versus warfarin were at significantly lower risk for hip fracture (aHR 0.60, 95% CI 0.48-0.74, P<0.001). Risk of vertebral fracture was significantly reduced as well with NOACs (aHR 0.76, 95% CI 0.66-0.88, P<0.001), nearly identical to the 0.79 hazard ratio reported in the meta-analysis (although that failed to achieve statistical significance).

Huang and his team also conducted their own meta-analysis involving fractures and osteoporosis diagnoses across 12 randomized controlled trials initially designed to compare the efficacy of NOACs and warfarin on stroke prevention and venous thromboembolism. Although evaluating a secondary outcome, their findings supported their primary analysis, with apixaban and rivaroxaban demonstrating the lowest risk of fracture, followed by dabigatran and warfarin.

For the study, Huang and his team selected patients who were prescribed NOACs or warfarin for at least 90 days to treat atrial fibrillation from Taiwan's National Health Insurance Research Database. Patients in the two groups were matched for propensity. The analysis was adjusted for age, sex, and the presence of many comorbidities (including diabetes, hypertension, chronic kidney disease, and stroke), as well as medications related to osteoporosis and fracture like corticosteroids, diuretics, and nonsteroidal anti-inflammatory drugs.

Overall, 8,571 patients were included in each of the NOAC and warfarin groups. About two-thirds of patients were 65 or older; mean age was 71. Just under 60% of patients were male in both the NOAC and warfarin cohorts, and rates of comorbidities and medication use were similar across groups.

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