Influence of Dietary Sodium and Potassium Intake on the Heart Rate Corrected-QT Interval in Elderly Subjects

It is well known that imbalances in the dietary electrolytes are associated with a significantly higher incidence of cardiovascular disease (CVD). On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of cardiac autonomic nervous system dysfunction, the incidence of CVD and sudden cardiac death. This study was designed to clarify the association between the nutritional status and the QTc interval in elderly subjects. The subjects included 119 elderly subjects (46 males and 73 females, age; 72.9±4.8 y) without a history of CVD, who were taking cardioactive drugs. Resting 12-lead electrocardiography was performed, while the QTc interval was calculated according to Bazett's formula. The nutritional status was assessed using a brief self-administered diet history questionnaire. The subjects were divided into three categories, which were defined as equally trisected distributions of the body mass index (BMI). The QTc interval was significantly longer in both the low and high BMI groups than in the moderate BMI group in both genders (p<0.05, respectively). A stepwise multiple regression analysis showed the QTc interval to be independently associated with the potassium intake in the low BMI group and the sodium intake in the high BMI group in both genders (p<0.05, respectively). These results suggest that the body mass, especially lean body mass and overweight, were associated with a prolonged QTc interval and dietary electrolytes in elderly subjects. Based on our results, we consider that it is necessary to perform dietary counseling, especially focusing on sodium and potassium intake, depending on the body mass.