Predictors of stable hypertension in young borderline subjects: a five-year follow-up study.

Forty-four young subjects with borderline hypertension underwent a 5-year follow-up. At the first examination their intralymphocytic Na+ (Nai) was measured before and after 1 month of a low-salt diet. Blood pressure and heart rate were recorded at rest (baseline), during mental arithmetic, and after the test (recovery). After 5 years, no subject with normal Nai developed hypertension, and, furthermore, subjects with normal Nai had no increase in blood pressure values. Thirty-one percent of subjects with high Nai developed hypertension. Subjects developing hypertension were characterized by a high pressor response to mental stress and by an increase in recovery diastolic blood pressure in comparison with baseline diastolic blood pressure. Sixty percent of the subjects whose recovery diastolic blood pressure was at least 6% higher than baseline developed hypertension. Eighty percent of subjects whose Nai was not reduced after the diet became hypertensive. Nai and diastolic blood pressure were unrelated at the first examination; however, a significant correlation was found between Nai recorded at first examination and diastolic blood pressure recorded after 5 years. It is concluded that Nai is a good predictor of future blood pressure in borderline subjects and that subjects with normal Nai have a very low risk of developing high blood pressure.