Does Alzheimer's disease protect against cancers? A nationwide population-based study

Background: Previous studies suggested a decreased risk of cancer among patients with Alzheimer's disease (AD). There is still a lack of data on the specific types of cancer, the risk factors, and the impact of cholinesterase inhibitors on developing cancer in AD. Methods: We performed a nationwide population-based study of 6,960 patients with AD between 1997 and 2006 using Taiwan's National Health Insurance database. Patterns of cancer incidence in AD patients were compared with those of the general population using standardized incidence ratios (SIRs). Results: Patients with AD had a reduced risk of developing overall cancer [SIR = 0.88, 95% confidence interval (CI) = 0.80-0.97]. Specifically, patients with AD were protected from lung cancers (SIR = 0.75, 95% CI = 0.57-0.98), especially men (SIR = 0.61, 95% CI = 0.40-0.88). In subgroup analyses, women, patients aged 60-79 years, and those diagnosed as having AD for more than 1 year were more likely to be protected from cancers. Conclusions: Our study demonstrates a decreased incidence of overall cancers in patients with AD, a finding lower than but consistent with Western countries. Patients with AD had a significantly decreased risk of lung cancer. Further investigation of genetic evidence linking AD to cancer is warranted.