In the current study that examined stroke, CHD, hypertension and type 2 diabetes that included both diagnosed and undiagnosed cases, participants with more CMDs had an increasingly higher risk of dementia after accounting for APOE ε4 allele and lifestyle factors; the highest HR (5.61) was observed for participants with four CMDs, suggesting a monotonic, additive relationship between increasing number of CMDs and dementia risk. The gene discussed is APOE; the disease is type 2 diabetes mellitus.