Effect of Apolipoprotein E ɛ4 Carrier Status on Cognitive Response to Acetylcholinesterase Inhibitors in Patients with Alzheimer’s Disease: A Systematic Review and Meta-Analysis

Abstract

Background: The apolipoprotein E ɛ4 (APOE ɛ4) genotype is the major genetic risk factor for Alzheimer’s disease (AD). However, its effect on an individual’s response to treatment is less well understood. Many studies have reported that the presence or absence of APOE ɛ4 may have influence on the therapeutic response for acetylcholinesterase inhibitors (AChEIs), but the results were inconsistent. This study performed a systematic review and meta-analysis to evaluate the association between response of treatment with AChEIs and the APOE ɛ4 carrier status. Methods: Clinical studies with AD patients reporting APOE ɛ4 genotype were included in the analysis. Cognitive outcome was measured by the change in Mini-Mental State Examination (MMSE), cognition subscales of the Alzheimer’s Disease Assessment Scale (ADAS-cog), or Cognitive Abilities Screening Instrument (CASI). A random effects model was employed to calculate the standardized mean difference (SMD) and odds ratio (OR). Results: Of the 284 screened abstracts, 38 studies were identified, 30 of which were included for meta-analysis. Continuous data for assessing the association between APOE ε4 and cognitive outcomes of AChEIs were available from 18 studies. The cognitive outcomes showed no significant difference between APOE ε4 carriers and APOE ε4 non-carriers (SMD = 0.022, 95% CI: –0.089∼0.133, p = 0.702, I2 = 55.3%). Twelve studies with binary data were included, also revealing insignificant difference between the two groups (OR = 1.164, 95% CI: 0.928∼1.459, p = 0.189, I2 = 16.4%). Subgroup analysis indicated that AChEIs were significantly more effective than placebo in both groups. Conclusions: APOE ɛ4 carrier status had no significant influence on the treatment response to AChEIs in patients with AD. AChEIs had a positive therapeutic effect compared with placebo regardless of APOE ε4 carrier status.