Serum Potassium Levels of 4.5 to Less Than 5.0 mmol/L Are Associated with Better Vascular Function

Aim: An experimental study showed that potassium inhibits the formation of reactive oxygen species by vascular cells. The purpose of this study was to investigate the association between serum potassium levels and vascular function. Methods: We measured flow-mediated vasodilation (FMD) as an index of endothelial function in 3045 subjects (1964 men; mean age, 62.3±13.8 years) and nitroglycerine-induced vasodilation (NID) as an index of vascular smooth muscle function in 1578 subjects (1001 men; mean age, 61.8±16.3 years). Results: In the 3045 subjects, there was a significant positive correlation between FMD and serum potassium levels (r=0.09,P＜0.001). Multivariate analysis revealed that serum potassium levels were significantly associated with FMD (β=0.109,P＜0.001). When subjects were divided into two groups based on treatment with drugs that could alter serum potassium levels, the association between serum potassium levels and FMD was significant both in subjects with (β=0.096,P＜0.001) and subjects without (β=0.123,P＜0.001) treatment with drugs that could alter serum potassium levels. In the 1578 subjects, there was a significant positive correlation between NID and serum potassium levels (r=0.11,P＜0.001). Multivariate analysis revealed that serum potassium levels were significantly associated with NID (β=0.098,P＜0.001). The association between serum potassium levels and NID was significant both in subjects with (β=0.121,P=0.001) and subjects without (β=0.083,P=0.03) treatment with drugs that could alter serum potassium levels. Conclusions: Serum potassium levels of 4.5-＜5.0 mmol/L are associated with better vascular function regardless of the presence or absence of treatment with drugs that could alter serum potassium levels.