Factors that influence the risk of neurocognitive decline and Alzheimer's disease (AD) may provide insight into therapies for both disease treatment and prevention. Although age is the most striking risk factor for AD, it is notable that the prevalence of AD is higher in women, representing two-thirds of case. The role of estrogen replacement therapy in reducing the risk of cognitive decline as well as dementia-related morbidity and mortality remains an active area of research. This perspective presents a testable working model of estrogen's relation to cognition with novel effect modifiers, including the degree of cholinergic dysfunction and the availability of choline from endogenous and exogenous sources. It also shows novel routes of investigation related to estrogen replacement and its interactions with menopausal timing, cholinergic signaling, and the influence of the endogenous (i.e., common PEMT variants) and exogenous (i.e., dietary) choline supply on cognitive function and risk of age-related cognitive decline and dementia.