Baseline sodium-lithium countertransport and 6-year incidence of hypertension: The Gubbio Population Study

Background: Sodium-lithium countertransport (Na-Li CT) activity is high in persons with hypertension. This study investigated whether high Na-Li CT relates to development of hypertension. Methods and Results: At the baseline visit of the Gubbio Population Study, 4210 people of the 5376 surveyed were 18 to 74 years old; of these, 1599 were hypertensive (systolic pressure ≤ 140 mm Hg, or diastolic pressure ≤90 mm Hg, or on antihypertensive drug therapy). Of the 2611 nonhypertensives, 302 did not have Na-Li CT measured and 580 did not participate in 6-year follow-up. This analysis, therefore, deals with data collected on 1729 men 18 to 74 years old and women 18 to 74 years old who at baseline were nonhypertensive and had Na-Li CT measurement. Compared with individuals who were nonhypertensive at baseline and follow- up, individuals with incident hypertension at follow-up (systolic pressure ≤140 mm Hg, or diastolic pressure ≤90 mm Hg, or on antihypertensive drug therapy) had higher baseline values of Na-Li CT, blood pressure, age, body mass index, plasma cholesterol, and alcohol intake (P < .05). Baseline Na-Li CT was positively associated (P < .05) with development of hypertension in quartile analysis, with highest incidence of hypertension among men and women with Na-Li CT in the highest quartile (for men, ≤376 and for women, ≤311 μmol Li·L red blood cells^-1 · h^-1). In univariate logistic regression, incidence of hypertension was related to baseline value of Na-Li CT, blood pressure, age, body mass index, plasma cholesterol, and alcohol intake (P < .05). In multiple logistic regression analysis, individuals with baseline Na- Li CT higher by 127 μmol (pooled SD for men and women) had 1.23 times greater risk of incident hypertension with control for sex and baseline age, body mass index, systolic pressure, and other confounders (P < .001). Conclusions: Na-Li CT is a predictor of hypertension risk in adults.