Blood pressure and life style in the People's Republic of China: three samples in the INTERSALT Study

Abstract

In INTERSALT, the International Cooperative Study on Electrolytes and Blood Pressure, three centres located in the People's Republic of China (PRC) had distinctive patterns of BP and of life style variables that, in INTERSALT overall, were found to relate to BP. The PRC centres had low body mass index (BMI) and alcohol consumption but high urinary sodium and sodium/potassium ratio (Na/K). Compared with 45 other INTERSALT centres, average BMI was 22.7 vs. 25.4 and alcohol consumption was 32% vs. 61%, with heavy drinking 3% vs. 14%. However, Na/K in the PRC was 6.7 vs. 3.2 in the other centres. This combination of factors may underlie the BP pattern observed. While mean BP in the PRC was lower than in the 45 centres (-7.0 mmHg SBP, -5.6 mmHg for DBP), this was counterbalanced by other findings. Upward slope of systolic pressure with age was 45% greater for the PRC than the other centres and 24% greater for diastolic pressure. As a result, although percentage hypertensive for ages 20-49 years for the PRC was half that in the 45 centres (6% vs. 12%), by age 50-59 years the prevalence was 31% in the PRC and 38% in the other centres. Hypertension prevalence in Tianjin, with highest Na/K in INTERSALT (7.6) was 40% for ages 50-59 years. While sample size in individual centres does not provide power to demonstrate aetiological relationships, these findings permit formulation of the following hypothesis: although lower body mass and lower alcohol intake may counteract to some degree impact of high salt intake, such intake over decades eventually takes its toll on BP.