Alzheimer's disease, Huntington's disease and cancer.

Neurodegenerative disorders and cancer are two of the most common groups of conditions in our world. Some studies have proposed that neurodegenerative disorders may be protective of the development of cancer. We tested this hypothesis using two neurodegenerative disorders with different molecular pathophysiology - Alzheimer's disease (AD) and Huntington's disease (HD) - to see if the inverse relationship between cancer and neurodegeneration was generalizable. Five-year cancer incidence was determined in two large datasets: AD using the C-Path Online Date Repository (CODR) database (n = 6383) and HD using the ENROLL-HD database (n = 2608). Cancer incidence was determined in the populations and compared to normal population data for Australia, United Kingdom and the United States of America. Age-sex standardized rates of cancer were determined and expressed as 95% confidence intervals. We describe an age-sex standardized cancer rate of 1179.6/per 100,000 population to 1253.7/per 100,000 population in normal populations. The rate in AD was 815.2/per 100,000 population (95% CI 813.32-817.5/per 100,000 population) and for HD 1296.6/per 100,000 population (95% CI 1288-1308.2/per 100,000 population). We conclude that patients with AD have a reduced age-sex standardized rate of developing cancer not shared with HD, a finding that hints at different molecular mechanisms.