Postoperative delirium after hip surgery is a potential risk factor for incident dementia: A systematic review and meta-analysis of prospective studies

•No meta-analysis has assessed the relationship between postoperative delirium and incident dementia after hip surgery.•Our meta-analysis revealed that postoperative delirium after hip surgery is a risk factor for incident dementia.•Early identification of cognitive function should be needed after surgery, especially in cases with postoperative delirium. Although a few trials have explored the relationship between postoperative delirium (POD) and incident dementia in patients with hip surgery, the numbers of participants in each study are relatively small. Thus, we performed a meta-analysis to examine whether POD after hip surgery is a risk factor for incident dementia. Six prospective cohort studies investigating the development of incident dementia in patients with POD after hip surgery were retrieved from PubMed, Embase, and the Cochrane Library. We performed a pairwise meta-analysis using fixed- and random- effect models. POD significantly increased the risk of incident dementia and cognitive decline (overall odds ratio [ORs] = 8.957; 95 % confidence interval [CI], 5.444–14.737; P