Inverse association for diagnosis of Alzheimer's disease subsequent to both melanoma and non-melanoma skin cancers in a large, urban, single-centre, Midwestern US patient population.

BACKGROUND: Although literature demonstrates a decreased risk of Alzheimer's disease (AD) in individuals with various cancers, including squamous cell cancers (SCC) and basal cell cancers (BCC) comprising non-melanoma skin cancers (NMSC), there is a paucity of literature to substantiate an association between malignant melanoma (MM) and AD. OBJECTIVE: The aim of this study was to determine whether an association exists between MM and AD as well as for NMSC and AD. METHODS: A large urban, Midwestern, US, single-centre, medical record (EMR) data repository was searched between January 2001 and December 2015, to identify all patients at age ≥60 and <89 years with a clinic follow-up of at least 1 year and no diagnosis for AD, MM or NMSC at the time of the study entry. Data collected included age, gender, race and duration of follow-up. MM and NMSC were detected by ICD-9 codes and ICD-10 codes. Incident diagnosis of AD was also detected by ICD-9 and ICD-10 codes. Logistic regression analysis was utilized to obtain crude and adjusted odds ratios (ORs). RESULTS: Data for a total of 82 925 patients with known race and gender and were detected. After adjusting for confounding factors (race, gender, age, cerebrovascular disease, peripheral vascular disease and diabetes), there was a significant decreased risk of subsequent AD in patients with MM (OR: 0.39; 95% CI: 0.16-0.96; P = 0.042) as well as in patients with BCC (OR: 0.18; 95% CI: 0.08-0.45; P < 0.0001) and for patients with SCC (OR: 0.08; 95% CI: 0.01-0.56; P = 0.013). CONCLUSION: These findings add to the growing body of evidence for a decreased risk of AD in patients with various cancers and highlight the need for ongoing research to elucidate both neurologic and biologic mechanisms that may underlie this apparent inverse association.