Multivitamin use and risk of stroke incidence and mortality amongst women.

BACKGROUND AND PURPOSE: Few studies have examined the association between multivitamin use and the risk of stroke incidence and mortality, and the results remain inconclusive as to whether multivitamins are beneficial.

METHODS: The associations between multivitamin use and the risk of incident stroke and stroke mortality were prospectively examined in 86 142 women in the Nurses' Health Study, aged 34-59 years and free of diagnosed cardiovascular disease at baseline. Multivitamin use and covariates were updated every 2 years and strokes were documented by review of medical records. Hazard ratios of total, ischaemic and hemorrhagic strokes were calculated across categories of multivitamin use (non-user, past, current user) and duration (years), using Cox proportional hazards models.

RESULTS: During 32 years of follow-up from 1980 to 2012, 3615 incident strokes were documented, including 758 deaths from stroke. In multivariate analyses, women who were current multivitamin users did not have a lower risk of incident total stroke compared to non-users [relative risk (RR) 1.02, 95% confidence interval (CI) 0.93-1.11], even those with longer durations of 15 or more years of use (RR 1.08, 95% CI 0.97-1.20) or those with a lower quality diet (RR 0.96, 95% CI 0.80-1.15). There was also no indication of benefit from multivitamin use for incident ischaemic or hemorrhagic strokes or for total stroke mortality.

CONCLUSIONS: Long-term multivitamin use was not associated with reduced risk of stroke incidence or mortality amongst women in the study population, even amongst those with a lower diet quality. An effect in a less well-nourished population cannot be ruled out.