Dietary glycemic index, glycemic load, and refined carbohydrates are associated with risk of stroke: a prospective cohort study in urban Chinese women

Background: Epidemiologic evidence on dietary carbohydrates and stroke risk remains controversial. Very few prospective cohort studies have been conducted in Asian populations, who usually consume a high-carbohydrate diet and have a high burden of stroke. Objective: We examined dietary glycemic index (01), glycemic load (GL), and intakes of refined and total carbohydrates in relation to risks of total, ischemic, and hemorrhagic stroke and stroke mortality. Design: This study included 64,328 Chinese women, aged 40-70 y, with no history of cardiovascular disease, diabetes, or cancer. A validated, interviewer-administered food-frequency questionnaire was used to assess usual dietary intakes at baseline and during follow-up. Incident stroke cases and deaths were identified via follow-up interviews and death registries and were confirmed by review of medical records and death certificates. Results: During mean follow-ups of 10 y for stroke incidence and 12 y for stroke mortality, we ascertained 2991 stroke cases (2750 ischemic and 241 hemorrhagic) and 609 stroke deaths. After potential confounders were controlled for, we observed significant positive associations of dietary 01 and GL with total stroke risk; multivariable-adjusted HRs (95% CIs) for high compared with low levels (90th compared with 10th percentile) were 1.19 (1.04, 1.36) for GI and 1.27 (1.04, 1.54) for GL (both P-linearity < 0.05 and P-overall significance < 0.05). Similar linear associations were found for ischemic stroke, but the associations with hemorrhagic stroke appeared to be J-shaped. Similar trends of positive associations with stroke risks were suggested for refined carbohydrates but not for total carbohydrates. No significant associations were found for stroke mortality after multivariable adjustment. Conclusion: Our results suggest that high dietary GI and GL, primarily due to high intakes of refined grains, are associated with increased risks of total, ischemic, and hemorrhagic stroke in middle-aged and older urban Chinese women.