Abstract
AIM: The associations between dietary saturated fatty acids and the risks of stroke subtypes in cohort studies were examined by a meta-analysis of separate ethnic Japanese and non-Japanese cohorts, and causes of their difference were elucidated. METHOD: Log hazard ratio (HR) with 95% confidence interval (CI) of the highest versus the lowest saturated fat intake from cohort studies were weighed by an inverse variance method to combine HRs. RESULTS: Five studies of intracerebral hemorrhage and 11 studies/comparisons of ischemic stroke were selected. A meta-analysis of intracerebral hemorrhage excluding subarachnoid hemorrhage showed a strong inverse association in Japanese (n=3, HR=0.55, 95% CI 0.32-0.94) but not in non-Japanese (n=2, HR=0.98, 95% CI 0.62-1.53). A meta-analysis of ischemic stroke showed a mild inverse association in Japanese (n=4, HR=0.82, 95% CI 0.71-0.93) but not in non-Japanese (n=7, HR= 0.93, 95% CI 0.84-1.03). The effect size of saturated fat in reducing the risk of stroke in Japanese was stronger for intracerebral hemorrhage (45% reduction) than for ischemic stroke (18% reduction). CONCLUSIONS: In Japanese but not in non-Japanese, a diet high in saturated fat is associated with a low risk of intracerebral hemorrhage and ischemic stroke. This may be due to differences in the range of intake of saturated fat, genetic susceptibility, incidence of lacunar infarction, and/or confounding factors such as dietary proteins. An intervention study targeting Japanese will be required to verify the causality.