Potassium intake is related to nocturnal blood pressure dipping

Abstract

Sodium restriction and high levels of dietary potassium may contribute to a greater nocturnal decline in blood pressure. To evaluate the association of nutrient intake with the nighttime blood pressure dip, we measured 24-hour sodium and potassium excretion and performed ambulatory blood pressure monitoring in a sample of 165 young men and women with normal or mildly elevated blood pressure. Participants included 85 African-Americans and 80 whites with an average age of 33±6 years. Daytime systolic blood pressure averaged 125±13 mmHg, with a mean nighttime dip of 16±7 mmHg. The 24-hour sodium excretion averaged 137±61 mEq/24 hr, and potassium excretion averaged 52±25 mEq/24 hr. African-Americans and whites had similar levels of sodium excretion (132±64 vs 144±58 mEq/24 hr, p=NS), but potassium excretion was significantly lower in African-Americans (38±24 vs 59±28 mEq/24 hr, p<0.001). The nocturnal dip in systolic blood pressure was correlated with potassium excretion (r=0.25, p<0.01), and this association remained significant after adjusting for race (p<0.05) and for daytime blood pressure (p<0.01). Subjects with low potassium excretion (≤50mEq/24 hr) and those with high potassium excretion (>50mEq/24 hr) were similar in age (34±6 vs 33±6 years, p=NS) and daytime systolic blood pressure (124±13 vs 127±12 mmHg, P=NS), but participants with low potassium excretion were more often African-American (72% vs 22%, p<0.01) and had a smaller nighttime systolic blood pressure dip (15±7 vs 18±7 mmHg, p<0.01). In contrast, low sodium intake was not associated with a greater nocturnal systolic blood pressure decline. These results suggest that potassium consumption may be an important determinant of the nocturnal fall in blood pressure, and that dietary factors may contribute to ethnic differences in diurnal blood pressure variation.