Cancer Risk And Alzheimer Disease: A Meta-analysis

Background: Alzheimer disease (AD) is considered to be associatedwith reduced cancer risk, but the existing evidences are controversial.Clarifying this association might improve understanding of the twodisorders.Objective: To examine the relation of cancer risk and AD ameta-analysis of published literatures on this subject was carried out.Methods: A PubMed, EMBASE and Web of Science search wasconducted in November2013. Pooled risk ratios (RRs) with theircorresponding95%confidence intervals (CIs) were obtained usingrandom-effects meta-analysis. We tested for publication bias andheterogeneity, and stratified for study characteristics, smoking-relatedcancers versus non-smoking-related cancers, and site-specific cancers.Results: Nine studies were included in this meta-analysis. Comparedto controls, the pooled RR of cancer in AD patients was0.55(95%CI,0.41-0.75), with significant heterogeneity among these studies (p＜0.001,I2=83.5%). Stratified analyses revealed that the reduced cancer risk wasmore substantial when we restricted our analyses to cohort studies, studies with adjusted estimates, studies defining AD by generally accepted criteria,and studies with longer length of follow-up. In sub-analyses forsite-specific cancers only lung cancer showed significant decreased risk(RR=0.72;95%CI,0.56-0.91), and the risk of prostate cancer increased inAD patients (RR=1.12;95%CI,0.84-1.48). We did not find significantpublication bias (p=0.251for Begg and Mazumdar’s test and p=0.143forEgger’s regression asymmetry test).Conclusion: The findings from this study support an associationbetween AD and decreased cancer risk.