Associations of serum n-3 and n-6 PUFA and hair mercury with the risk of incident stroke in men: the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD).

PUFA have been associated with lower risk of CVD, but less is known about their association with stroke risk. Fish, a major source of n-3 PUFA, may also contain methylmercury, which has been associated with higher risk of CVD and attenuation of the benefits of long-chain n-3 PUFA. We investigated the associations of serum n-3 and n-6 PUFA and hair Hg with risk of stroke in men. A total of 1828 men from the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42-60 years and free of CVD at baseline in 1984-1989 were studied. Cox regression models were used for the analyses. During the mean follow-up of 21·2 years, 202 stroke cases occurred, of which 153 were ischaemic strokes. After adjustment for age and examination year, the only statistically significant association among the n-3 and n-6 PUFA was observed between the n-3 PUFA α-linolenic acid and risk of haemorrhagic stroke (hazard ratio in the highest v. the lowest quartile 0·33; 95 % CI 0·13, 0·86; P trend=0·03). However, further adjustments attenuated the association to statistically non-significant. Hair Hg was not associated with stroke risk, but among those with hair Hg above the median level, higher serum long-chain n-3 PUFA concentrations were associated with a higher risk of ischaemic stroke. In our cohort of men, serum n-3 or n-6 PUFA or hair Hg were not associated with stroke risk; however, the interaction between Hg and long-chain n-3 PUFA with regard to ischaemic stroke risk warrants further investigation.