Cardiovascular diseases are the #1 cause of morbidity and mortality in older adults. Elevated arterial blood pressure (BP), especially systolic BP (SBP), is the primary contributor to cardiovascular disease in the elderly. The key experimental goal of the current award was to determine if regular aerobic exercise decreases SBP and arterial stiffness as much or more than moderate dietary sodium restriction (SR) in postmenopausal women with elevated baseline levels of SBP. Preliminary results indicate that in contrast to the working hypotheses: a) SR produced much greater reductions in SBP than exercise (15 vs 2.5 mmHg); and b) only SR reduced our indirect measures of arterial stiffness, and only in the """"""""central"""""""" (carotid and aorta) arteries; neither intervention altered measures of peripheral arterial stiffness. Moreover, the SR-induced reductions in SBP correlated with the decreases in estimated central arterial stiffness. These preliminary observations suggest that SR may lower SBP in older adults with systolic hypertension by increasing central arterial compliance. However, this hypothesis and hypotheses related to the mechanism by which this effect is mediated can only be tested in prospective studies in which central arterial compliance is directly measured using a combination of high-resolution ultrasonography and arterial applanation tonometry. Accordingly, in the present competitive renewal application plans are to test the following hypotheses-in older adult humans with Stage 1 systolic hypertension (SBP=140-159 mmHg): 1) SR will increase central arterial compliance; 2) among individual subjects the increases in central arterial compliance will be strongly and inversely related to the reductions in SBP; and 3) the increases in central arterial compliance will be due, at least in part, to a decrease in the tonic suppressive influence exerted by the sympathetic-adrenergic system. A total of 60 otherwise healthy adult men and women aged 60-80 years with systolic essential hypertension and a diastolic BP <99 mmHg will be studied at baseline and then randomly assigned to 12 weeks of either SR or attention control (n=30 each, 15 men/15 women). At the end of 12 weeks of SR or control, subjects will be studied again. Subjects completing the attention control condition will be given the opportunity to informally participate in SR so that they may also receive the hypothesized benefits. This would be the first intervention study to determine the mechanistic role played by increases in central arterial compliance and its sympathetic-adrenergic modulation in the clinically important SBP-lowering effects of SR in older adult humans with systolic hypertension.
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