Sodium-lithium countertransport genotype and the probability of hypertension in adults

The objective of the present study was to determine whether information about a biometrically inferred single gene with large effects on erythrocyte sodium-lithium countertransport is useful in predicting the probability of having hypertension. We used multivariate logistic regression to model the relationship between the probability of having hypertension and predictor traits in a sample of 382 unrelated adult women and 347 unrelated adult men from Rochester, Minn. First, we identified a set of demographic, biochemical, and physiological predictors. Second, we analyzed whether the relationship between the probability of having hypertension and the identified predictor traits was heterogeneous between the biometrically inferred single locus genotypes with large effects on sodium-lithium countertransport level. Third, if there was no heterogeneity, we assessed whether sodium-lithium countertransport genotypes made an additional contribution to predicting the probability of having hypertension after other predictors were considered. In women, the predictors of the probability of having hypertension were age, plasma apolipoprotein CIII, body mass index, and an interaction term involving age and body mass index. The relationship between the probability of having hypertension and the identified predictors was not heterogeneous between sodium-lithium countertransport genotypes, and genotype did not contribute to the prediction of the probability of having hypertension after the identified predictors were considered. In men, predictors of the probability of having hypertension were age, plasma levels of high-density lipoprotein cholesterol, apolipoproteins AI and CII, sodium-lithium countertransport level, and sodium-lithium countertransport genotype. The relationship between the probability of having hypertension and sodium-lithium countertransport level and age were heterogeneous between biometrically inferred sodium-lithium countertransport genotypes. For a given increase in sodium-lithium countertransport level, the odds of having hypertension increased 5.2 times more in men with the genotype associated with elevated levels of sodium-lithium countertransport than in men with alternative genotypes. For a given increase in age, the odds of having hypertension increased 3.4 times more in men with the genotype associated with elevated levels of sodium-lithium countertransport than in men with alternative genotypes. These results reject the null hypothesis that information about allelic variation at a single gene that influences sodium-lithium countertransport level does not improve the ability to predict the probability of having hypertension in men after other predictors have been considered.