Osteoporosis treatment and atrial fibrillation: alendronate versus raloxifene.

OBJECTIVES

Concerns have been raised about bisphosphonate use and risk of atrial fibrillation (AF) in women with osteoporosis. This study compares the risk of AF and of flutter or acute myocardial infarction (AMI) in women with osteoporosis taking alendronate or raloxifene.

METHODS

Using Taiwan's National Health Insurance database to conduct a population-based retrospective cohort study, we reviewed the medical and prescription histories of 27,257 women with osteoporosis (21,037 receiving alendronate and 6,220 receiving raloxifene) between 2001 and 2007. Mean (SD) follow-up was 303.62 (422.87) days. For the main outcome measures, we calculated the adjusted relative risk of AF and AMI using the Cox proportional hazards model, adjusting for various confounders.

RESULTS

Incidence rates (per patient-year) of AF in the alendronate group (1.00%) and the raloxifene group (1.02%) were similar. Alendronate use was not associated with risk of AF (hazard ratio [HR], 1.06; 95% CI, 0.85-1.32) and AMI (HR, 1.02; 95% CI, 0.86-1.19) compared with raloxifene use. However, alendronate users who had previous cardiovascular events and had taken their medications for more than 1 year were at significantly greater risk of AMI than were the group taking raloxifene (HR, 2.24; 95% CI, 1.07-4.71). Users who received 70 mg of alendronate once a week were at significantly lower risk of AF than were those taking 10 mg daily (HR, 0.56; 95% CI, 0.47-0.68).

CONCLUSIONS

Compared with raloxifene, alendronate did not increase the risk of AF and flutter in women with osteoporosis. Medical history contributed most to the development of AF or AMI in the women who received either raloxifene or alendronate. Long-term treatment with alendronate is not suggested for women with a history of cardiovascular events because they are at increased risk of AMI.