Association between Alzheimer's Disease and Cancer Risk in South Korea: an 11-year Nationwide Population-Based Study.

Background And Purpose: Previous studies have suggested a decreased cancer risk among patients with Alzheimer's disease (AD). There remains a lack of data on the specific types of cancer and risk factors for developing cancer in AD. We evaluated the association between AD and cancer risk, and we examined specific types of cancer.

Methods: A population-based longitudinal study was conducted using the National Health Insurance Service-Senior cohort for 2002-2013. A total of 4,408 AD patients were included in the study, as were 19,150 matched controls. Potential associations between the risk of cancer and AD were analyzed using Cox proportional hazard regressions.

Results: Cancer developed in 12.3% of the AD group patients and in 18.5% of control group subjects. AD was associated with a reduced risk of cancer (hazard ratio [HR], 0.70; 95% confidence intervals, 0.64-0.78). The risk of head and neck cancers was significantly reduced (HR, 0.49), as were risks for cancers of the digestive tract, including stomach cancer (HR, 0.42), colorectal cancer (HR, 0.61), liver and biliary tract cancers (HR, 0.68), and pancreatic cancer (HR, 0.55). Lung and prostate cancer risks were also significantly lower for the AD group (HR, 0.52 and HR, 0.72, respectively).

Conclusions: Our results showed an inverse association between AD and cancer. Further research involving a large number of patients in a hospital based-study is needed to address the biological associations between cancer development and dementia, including AD.