Background and purpose: Few studies have examined the association between folate intake and risk of stroke, although numerous studies have suggested that high levels of homocysteine are positively related to stroke. We aim to assess the relation between folate intake and stroke incidence among women participating in the Nurses' Health Study.
Methods: 83,272 female nurses aged 34 to 59 years in 1980 and residing in 11 US states were followed-up for 18 years. Follow-up questionnaires were sent biennially to update information on diet and to identify newly diagnosed cases of stroke and other illnesses.
Results: During 1,379614 person-years of follow-up from 1980 to 1998, we identified 1140 incident cases of stroke. Using age-adjusted and multivariable-adjusted models, no appreciable association between the intake of folate and total incidence of stroke was observed [relative risk in the multivariable-adjusted model for the highest quintile of folate intake (median=696 microg/d) compared with the lowest quintile (median=158 microg/d) was 1.01 (95% confidence interval [CI]: 0.79 to 1.29), P for trend=0.8]. Similar null results were found in secondary analyses on stroke subtypes (ischemic, thrombotic, embolic, subarachnoid hemorrhage, intraparenchymal hemorrhage) and in analyses that separately assessed dietary folate (excluding supplement users) and folate supplement intake.
Conclusions: Folate intake was not associated with incident stroke among women participating in the Nurses' Health Study.