Blood pressure, cholesterol, and stroke in eastern Asia

Background Stroke is a major cause of death and disability in most populati ons of eastern Asia, and the incidence, particularly of haemorrhagic stroke , is generally higher than in western populations. This study aimed to asse ss the contributions of blood pressure and blood cholesterol concentrations to stroke risk in populations from eastern Asia. Methods The project included 13 cohorts from the People's Republic of China and five from Japan (124774 participants, 837 214 person-years of observat ion). All 18 cohorts provided data on blood pressure and 12 (69767 particip ants) provided data on cholesterol concentrations. Parametric and non-param etric analyses were done, with adjustments for several potential confoundin g factors. Analyses were based on estimated usual diastolic blood pressure and cholesterol concentration during follow-up, rather than baseline measur ements, to avoid regression dilution bias. Findings Overall mean blood pressure was 124/78 mm Hg and mean cholesterol concentration was 4.5 mmol/L. 1798 strokes occurred; 751 (42%) were classif ied as haemorrhagic and 707 (39%) were confirmed by computed tomography or necropsy. Each 5 mm Hg lower usual diastolic blood pressure was associated with lower risk of. non-haemorrhagic stroke (odds ratio 0.61 [95% CI 0.57-0 .66]) and lower risk of haemorrhagic stroke (0.54 [0.50-0.58]). With decrea sing cholesterol concentrations there were trends towards a decrease in ris k of non-haemorrhagic stroke (odds ratio for 0.6 mmol/L decrease, 0.77 [0.5 7-1.06]) and an increase in risk of haemorrhagic stroke (1.27 [0.84-1.91]). Overall, there was no clear evidence of any interaction between cholestero l and diastolic blood pressure. Interpretation Blood pressure is an important determinant of stroke risk in eastern Asian populations, whereas cholesterol concentration is less impor tant, affecting the proportions of stroke subtypes more than overall stroke numbers. The association between blood pressure and stroke seems stronger than in western populations; a population-wide reduction of 3 mm Hg in dias tolic blood pressure should eventually decrease the number of strokes by ab out a third.