Association between cancer and Alzheimer's disease: systematic review and meta-analysis.

This study examined the association between cancer and Alzheimer's disease (AD) by a quantitative meta-analysis of cohort studies. Studies were identified by searching PubMed database through 1966 to December 2013 using the terms "Alzheimer's disease", "neoplasm", and "cancer". Six studies met the inclusion criteria in the overall meta-analysis. We pooled effect sizes using fixed-effects and random-effects models. Furthermore, we also tested for heterogeneity and publication bias. The results suggested that individuals diagnosed with AD had a decreased risk for incident cancer by 42% (95% CI, 0.40-0.86; p < 0.05), and patients with a history of cancer had a 37% decreased risk of AD (RR = 0.63; 95% CI, 0.56-0.72; p = 0.495). The Egger's test for publication bias (p = 0.280) showed no significant evidence for bias in the data from studies on AD and cancer risk. In summary, our meta-analysis demonstrated an inverse association between cancer and AD.