Systolic and diastolic blood pressures and urinary sodium excretion in mainland China

Sir, The relationship of sodium intake to blood pressure and prevalence of hypertension has remained somewhat controversial for many years, despite a large body of evidence from experimental and epidemiological studies across populations supporting a positive correlation between sodium and blood pressure. The report by Cheung et al.1 of a positive correlation between diastolic blood pressure and urinary sodium excretion in 70 hypertensive Hong Kong Chinese patients tends support to the findings of an earlier and much larger nationwide survey of blood pressure, hypertension and sodium intake in 950 356 men and women carried out in mainland China in 1991.2 A positive within‐population relationship between sodium intake and blood pressure has been demonstrated in several studies in mainland China, using values of either dietary or urinary sodium.2–5 For instance, in a study of 663 men and women in Tianjin,6 after adjusting for confounding variables, both dietary and urinary sodium and sodium/potassium ratio were significantly and positively correlated with blood pressure. Another population study of the relation between sodium intake and blood pressure conducted in 705 men and women aged 40–59 from two population samples of farmers (one from Shanxi in northern China and the other from Guangxi in southern China) and one of fisherman from Zhejiang of eastern China showed a significant positive association of sodium intake with both systolic and diastolic blood pressures.7