A high protein intake may reduce the risk of stroke but epidemiologic data on protein intake in relation to stroke risk are limited and inconsistent. Our objective was to test the hypothesis that protein intake would be inversely associated with risk of stroke.
We conducted a population-based prospective cohort study consisting of 34,670 Swedish women who were free of cardiovascular disease and cancer in 1997. Diet was assessed with a food-frequency questionnaire. Incident cases of stroke were ascertained from the Swedish Hospital Discharge Registry. We estimated relative risks (RR) with 95% confidence intervals (CI) using Cox proportional hazard regression model. During 10.4 years of follow-up, 1680 stroke events were identified, including 1310 cerebral infarctions, 154 intracerebral hemorrhages, 79 subarachnoid hemorrhages, and 137 unspecified strokes. Intake of total and animal protein, but not vegetable protein, was statistically significantly inversely associated with risk of total stroke and cerebral infarction after adjustment for other risk factors for stroke. The multivariable RRs of total stroke for the highest versus lowest quintile of intake were 0.74 (95% CI: 0.61, 0.91; P for trend = 0.006) for total protein and 0.71 (95% CI: 0.57, 0.88; P for trend = 0.01) for animal protein. The associations were stronger in women with a history of hypertension (RR of total stroke = 0.56; 95% CI: 0.40, 0.78 for highest versus lowest quintile of total protein).
These findings suggest that dietary protein intake is inversely associated with risk of stroke in women with hypertension.