Subtypes of mild cognitive impairment in older postmenopausal women: the Women's Health Initiative Memory Study.

Mild cognitive impairment (MCI) is a transitional state between normal cognitive functioning and dementia. A proposed MCI typology classifies individuals by the type and extent of cognitive impairment, yet few studies have characterized or compared these subtypes. Four hundred forty-seven women 65 years of age and older from the Women's Health Initiative Memory Study were classified into the 4 MCI subgroups and a "no impairment" group and compared on clinical, sociodemographic, and health variables. A cognitive deficit in at least 1 domain was present in 82.1% of participants, with most (74.3%) having deficits in multiple cognitive domains. Only 4.3% had an isolated memory deficit, whereas 21.3% had an isolated nonmemory deficit. Of the 112 women who met all MCI criteria examined, the most common subtype was amnestic multidomain MCI (42.8%), followed by nonamnestic multiple domain MCI (26.7%), nonamnestic single domain (24.1%), and amnestic single domain MCI (6.3%). Subtypes were similar with respect to education, health status, smoking, depression, and prestudy and onstudy use of hormone therapy. Despite the attention it receives in the literature, amnestic MCI is the least common type highlighting the importance of identifying and characterizing other nonamnestic and multidomain subtypes. Further research is needed on the epidemiology of MCI subtypes, clinical and biologic differences between them, and rates for conversion to dementia.