Homocysteine, estrogen and cognitive decline

Abstract

Background Factors that contribute to cognitive decline in women from midlife remain poorly understood. There are circumstantial data indicating a positive association between homocysteine and cognitive decline and that endogenous and exogenous estrogen may influence homocysteine levels. The aim of this review was to establish what is known of the relationships between cognitive change and homocysteine levels, and the impact of the menopause transition and exogenous estrogen on homocysteine levels.Methods We reviewed the recent published literature from 1993 to 2005 pertaining to the current understanding of the relationship(s) between plasma homocysteine levels and cognitive functioning and endogenous hormone levels and exogenous estrogen use in women.Results Hyperhomocysteinemia is consistently associated with cognitive decline. Dietary supplementation with vitamins may assist in normalizing homocysteine levels; however, there is no evidence that this results in favorable effects on cognition. Changes in endogenous estrogen levels are inversely associated with changes in serum homocysteine. Consistent with this, estrogen therapy is associated with reductions in plasma homocysteine, with the greatest effects reported in women with higher levels of homocysteine at baseline. Limited data indicate that tibolone is associated with little change in homocysteine. The use of raloxifene, the most studied selective estrogen receptor modulator, is associated with a modest reduction in homocysteine.Conclusions There are data to suggest an underlying link between homocysteine levels and cognitive decline. There is also evidence for a link between both the menopause transition and use of exogenous estrogen therapy and homocysteine levels. Clinical data do not support a role for exogenous estrogen in the prevention of dementia in older women; however, the ‘window of opportunity’ theory suggests that there is a need for randomized controlled trials to evaluate the role of estrogen in the early postmenopausal years to protect against cognitive decline in later life.