The association between delirium and the apolipoprotein E epsilon 4 allele: new study results and a meta-analysis

OBJECTIVES: To determine a possible association between Apolipoprotein E (APOE)sigma4-allele and delirium in a large cohort and combining these current data with former studies in a meta-analysis. Design: Combination of a new prospective cohort study and meta-analysis. SETTING: Medical department and orthopedic/traumatology department of University hospital from 2003 to 2007. Participants: A total of 656 patients aged 65 years and older acutely admitted with a medical diagnosis or after hip fracture. MEASUREMENTS: Confusion Assessment Method for delirium, Informant Questionnaire on Cognitive Decline-short form for predelirium global cognitive impairment, and Katz Index of Activities of Daily Living for functionality. APOE was genotyped by mass spectrometer. A meta-analysis was performed combining the current data with published studies analyzing the association between the APOE sigma4-allele and the delirium. RESULTS:: The 49% of the 76 surgical patients and 35% of the 580 medical patients experienced delirium. Delirious patients were significantly older (82 versus 77 years) and had more frequently functional (66% versus 26%) and cognitive impairment (86% versus 29%) than nondelirious patients. The odds ratio (OR) for delirium adjusted for age, cognitive, and functional impairment of sigma4 carriers compared with non-sigma4 carriers was 1.7 (95% confidence interval [CI]: 1.1-2.6). Four studies were added to the meta-analysis, which included 1,099 patients in total. The OR for delirium in the meta-analysis was 1.6 (95% CI: 0.9-2.7) of sigma4 carriers compared with non-sigma4 carriers. CONCLUSIONS: This study and meta-analysis suggest an association between delirium and the APOE sigma4 allele