Dementia and Alzheimer disease incidence rates do not vary by sex in Rochester, Minn.

Abstract

Incidence rates of Alzheimer disease (AD) were higher in women than in men in several recent European and Asian studies. Cohort studies in the United States, on the other hand, have consistently reported no difference in incidence across sex. To measure age- and sex-specific incidence rates of dementia and AD for persons aged 50 years and older residing in Rochester, Minn, during 1985 to 1989. Cases were ascertained through the medical records linkage system of the Rochester Epidemiology Project, which encompasses the records of all medical care providers (including outpatient clinics, hospitals, general practitioners, and nursing homes) in Rochester. Computer indices of clinical diagnoses, histologic diagnoses, and medical procedures were screened for indications of dementia. All medical records of potential cases were reviewed and abstracted by a trained nurse abstractor. A neurologist (E.K.) confirmed the presence of dementia and established a differential diagnosis of AD using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and estimated the year of onset. A total of 482 incident cases of dementia were identified; 356 of them (73.9%) had AD. For both dementia and AD, incidence rates increased steeply with age, and there were no consistent differences between men and women. The sex pattern for AD did not change after removing cases with silent bilateral infarcts on imaging. Contrary to observations from European and Asian populations, women were not at increased risk of incident AD in Rochester. Our findings, based on a medical records linkage system, corroborate findings from several other US studies that involved the direct contact of cohort members. The consistency of findings across study designs suggests that sex or sex-related exposures do not consistently play a major role in AD causation in American populations.