Predictive value of sodium/lithium countertransport on blood pressure changes in middle-aged men: a 7-yr follow-up study.

An elevated red blood cell sodium/lithium countertransport (Na/Li CT) is associated with high blood pressure and metabolic abnormalities. To evaluate the predictive power of Na/Li CT with regard to changes in blood pressure (BP) over time, we examined a group of men participating in the 7-yr follow-up of the Olivetti study, a prospective investigation of coronary heart disease risk factors in Naples, Italy. One twenty six untreated middle-aged men had Na/Li CT measured both in 1987 and 1994. Na/Li CT was highly stable over time (1987: 285±95; 1994 293±104 μmol × 1 RBC−1 × h−1; Pearsonʹs correlation coefficient between the two measurements 0.80, p<0.001). In simple linear correlation analysis, Na/Li CT was directly and significantly related to BP, body mass index (BMI), plasma triglyceride, glucose and uric acid concentrations both in 1987 and in 1994. Baseline Na/Li CT was significantly associated with systolic BP change over time (r=0.161, p<0.05). In multivariate analysis this association was statistically significant and independent from baseline values of age, BMI, triglyceride, glucose and BP (p<0.02). When the population was divided into quintiles of baseline Na/Li CT, individuals in the fifth quintile showed a the 7-yr systolic BP increase of 5.9 mmHg higher as compared with quintiles 1-4 (+9.1±2.7 vs 3.2±1.2 mmHg, p<0.05). A high level of Na/Li CT appears to be a significant and independent predictor of subsequent BP increase in previously normotensive middle-aged men.