Salt intake and blood pressure in the general population: a controlled intervention trial in two towns

Abstract

A controlled trial was conducted in two Belgian towns to investigate the feasibility and effects of a reduction in salt consumption at the community level. The low-sodium intervention in one town was mainly directed at women and implemented through mass media techniques, while the control town was merely observed. Cross-sectional random sampling at baseline and 5 years later was employed, the participation rate being similar (67%) in the two towns. During the study a total of 2211 subjects were examined. In adult women (.gtoreq. 20 years) in the intervention town the 24-h urinary excretion of sodim (UVNa) decreased by 25 mmol/24 h (P < 0.001) and this reduction differed (P = 0.01) from the concurrent trend in UVNa in the control town (+8 mmol/24 h). However, both systolic (SBP, -7.5 versus -7.9 mmHg) and diastolic (DBP, -2.3 versus -3.0 mmHg) pressures declined to a similar extent in the women from the two towns. In adult men in the intervention town, decreases were observed in UVNa (-12 mmol/24h) and in SBP (-5.6 mmHg) and DBP (-2.4 mmHg), but these trends were not significantly different from the concurrent changes in the control town (-14 mmol/24h, -4.9 and +0.2 mmHg, respectively). In addition to being greater in women than in men, the intervention effect on UVNa also tended to increase with age in both: in subjects aged 50 years or more, UNVa decreased in the intervention town by 25 mmol/24 h (P < 0.001) and this reduction differed (P < 0.01) from the concurrent trend in the control town (+ 17 mmol/24 h). However, blood pressure changes were similar in the intervention and control towns (SBP, -6.7 versus -8.3 mmHg; DBP, -2.4 versus - 2.8 mmHg, respectively). In conclusion, a reduction in salt consumption is difficult to achieve with mass media techniques. In women and in subjects aged 50 years or more, the intervention did achieve some success, but blood pressure was not affected.