Repetitive Behaviors in Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background: Repetitive behaviors (RBs) are a well-known symptom of Alzheimer's disease (AD); however, they have been little studied and have not been the subject of any specific literature review. Objective: To conduct a systematic review of all studies to document RBs in AD. Methods: An extensive literature search combining five databases and a meta-analysis were conducted to investigate the frequency, nature, and cognitive correlates of RBs in AD. Results: Ten studies were included in the review. Seven studies out of ten investigated the frequency of RBs in patients with AD, which ranged from 52.3% to 87%. A meta-analysis showed an overall frequency of 66.3% (95% CI: 55.5; 77.1) of patients exhibiting RBs in AD, but important heterogeneity was observed between studies. Three studies investigated the predominant nature of RBs in AD. Verbal RBs, complex behavioral stereotypies, and simple motor stereotypies have been identified to different degrees depending on the level of dementia. Most verbal RBs are underpinned by episodic memory impairment, while simple motor stereotypies and complex behavioral stereotypies are mostly underpinned by executive dysfunction. Conclusions: The current review seems to suggest that there are two types of mechanisms underpinning RBs involved in AD. The first is observed especially in the mild stages of the disease and is mediated by episodic memory impairment. The second occurs later and is mediated by executive impairment. Additional studies should be conducted to improve the knowledge about RBs in AD and thus improve their management.