Introduction: Medications with anticholinergic activity (MACs) are used to treat diseases common in older adults. Evidence on the association between anticholinergic burden (AB) and increased risk of fractures and osteoporosis or reduced bone mineral density (BMD) is inconsistent. Our aim was to conduct a systematic review of observational studies on AB with fractures and osteoporosis or reduced BMD and provide methodological appraisal of included studies.
Methods: We searched MEDLINE, EMBASE, Science Citation Index and CENTRAL as well as grey literature from database inception up to August 2020. Eligibility criteria were: observational design, AB-exposure measured through a scale, fracture of any type or osteoporosis or reduced BMD as outcome, and reported measure of association between exposure and outcome. No restrictions related to time, language or type of data were applied. Eligibility and risk of bias assessment as well as data extraction were performed independently by two reviewers. Risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale and the RTI Item Bank.
Results: The majority of the nine included studies had low risk of bias but heterogeneous methodology. No study used a new user design. Seven studies reported an increased risk of fractures associated with AB. In four studies using the Anticholinergic Risk Scale (ARS), adjusted risk of fractures was increased by 2-61% for ARS = 1, by 0-97% for ARS = 2, by 19-84% for ARS = 3, and by 56-96% for ARS ≥ 4; in three studies the ARS was aggregated, risk increased by 39% for ARS = 1-2 and 17% for ARS = 2-3. Two studies reported increased risk of fractures of 14 and 52% in the highest AB-category and one study reported that change in ARS of ≥ 3 during hospitalization was associated with a 321% increased risk in fractures. Two studies did not find an association between AB and fractures. The association between AB and osteoporosis or reduced BMD could only be assessed in two studies, one reporting increased risk of lower BMD at Ward's triangle, the other reporting no association between AB and BMD T-score change at the femoral neck.
Discussion: Our study suggests an association between AB and increased risk of fractures with possible dose-exposure gradient in studies using the ARS. The low number of studies and heterogeneity of methods calls for the conduct of more studies. We conducted a study investigating the risk of fractures associated with anticholinergic burden, which is the result of taking one or more medication with anticholinergic activity. The results of our study suggest that persons who experience anticholinergic burden might have a higher risk of fractures. However, since we were only able to include nine studies, more studies conducted in a similar way are needed.