Incidence of hypertension in individuals with different blood pressure salt-sensitivity: results of a 15-year follow-up study

Objective To evaluate the incidence of hypertension and the rate of decline in renal function in a sample of 47 Olivetti Heart Study ( OHS) participants whose blood pressure ( BP) salt-sensitivity and renal tubular sodium handling had been assessed in 1987-88. Methods During the 2002-04 OHS follow-up examination, medical history, physical examination and blood and urine sampling were performed in 36 of the 47 participants to the baseline study (age 60 +/- 6 years; average follow-up =15.1 +/- 0.6 years). The renal length was measured in 23 participants by kidney ultrasonography. Based on the baseline salt-sensitivity evaluation, the subjects were classified into a lower salt-sensitivity (LSS, n=20) and a higher salt-sensitivity group (HSS, n=16). Results In comparison with the LSS group, HSS participants had a significantly higher incidence of hypertension (87.5 versus 50.0%, P=0.02), a higher glomerular filtration rate ( median, first to fourth quartile: 81.9, 72.3-95.2 versus 72.3, 59.9-81.2 ml/min; P=0.03) and greater kidney length ( median, first to fourth quartile: 68.2, 63.3-72.1 versus 61.9, 58.7-62.7 mm/m of height; P=0.003). The incidence of hypertension remained significantly higher in HSS individuals after adjustment for age, intercurrent changes in body mass index and baseline blood pressure on low sodium diet (P=0.04). Conclusion Our findings indicate that individuals with higher BP salt-sensitivity have a higher rate of incident hypertension and suggest an altered renal tubular sodium handling involving a trend to increased glomerular filtration rate and blood pressure over time as a possible mechanism.