Alzheimer's disease and dementia rates do not vary by sex, according to a study of Minnesota residents by researchers at the Mayo Clinic.

Incidence rates of Alzheimer's disease were higher in women than in men in several recent European and Asian studies. However, studies in the United States have consistently reported no difference in incidence between men and women.

Researchers conducted a study to measure age- and sex-specific incidence rates of Alzheimer's disease and dementia for people age 50 years and older living in Rochester, Minnesota from 1985 to 1989.

Medical records were examined and a neurologist confirmed the presence of dementia and established whether the cause was Alzheimer's disease, also estimating the year of onset.

A total of 482 cases of dementia were identified, of which 356 (73.9 percent) were Alzheimer's disease. For both dementia and Alzheimer's disease, incidence rates increased steeply with age, and there were no consistent differences between men and women, according to the study reported in the Archives of Neurology.

"Contrary to observations from European and Asian populations, women were not at increased risk of incident Alzheimer's disease in Rochester," concluded the researchers.

"Our findings, based on a medical records linkage system, corroborate findings from several other U.S. 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 Alzheimer's disease causation in American populations," the researchers said.

Other sources: Archives of Neurology