Sex differences in item and associative memory among older adults with amnestic mild cognitive impairment

In older adults without cognitive impairment, women have an advantage over men in verbal memory tests; however, whether women with amnestic mild cognitive impairment (aMCI) exhibit this advantage remains controversial. We evaluated sex-specific differences in older adults with and without aMCI in item and associative verbal memory by using an associative memory task with immediate and delayed recognition conditions. The associations between memory task performances and medial temporal morphometric measures were examined. The study included 49 individuals with aMCI and 55 healthy older adults (HOs). The results revealed that a female advantage in immediate item and delayed associative memory was evident in HOs, and the female advantage in associative memory persisted even after item memory performance was controlled. By contrast, the female advantage was absent in individuals with aMCI; such women had more associative false alarms than men with aMCI. Furthermore, decreases in item memory, associative memory, and cortical thickness in the perirhinal and entorhinal regions in individuals with aMCI versus their sex-matched controls were more prominent in women than in men. The relation between brain structure and associative memory function was evident only for women, indicating that women and men may have different cognitive and neural mechanisms for processing associative memory. These findings support the concept of cognitive reserve in women during normal aging. Accounting for sex differences in verbal memory performance is crucial to improve aMCI identification, particularly for women.