STRESS, SODIUM, AND BLOOD PRESSURE REGULATION

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This will be longitudinal study of 128 healthy subjects with normal or minimally elevated blood pressure aged 20 to 40 years, who are exposed to regular cyclical variations of occupational stress. It will investigate the interactions of stress, family history of hypertension and sodium intake on blood pressure and related variables. Subjects will be selected from screened populations at Certified Public Accountant (CPA) or architectural firms in New York City. They will be divided into two groups of 64 subjects each: those with a positive family history of hypertension, and those without. They will be studied during a 4 month periods, which will encompass a transition from relatively low stress to a peak at the time of a deadline. Half of the subjects in each group will be randomized to take slow release sodium capsules to increase their dietary sodium by 100 meq/day, and the other half matching placebo. Baseline evaluation of the two groups will be performed during a period of low occupational stress, and will include a dietary evaluation, an ambulatory 24 hour blood pressure recording, and a series of questionnaires evaluating occupational stress, personality and demographical variables. Blood and urine samples will be taken for measures related to sodium balance (plasma renin, atrial natriuretic factor, urine aldosterone, and electrolytes) and stress (blood lipids and cortisol, and urine catecholamines and cortisol). During the experimental periods, which will last 17 weeks for the CPAs, subjects will keep records of their blood pressure both at work and at home, and also diaries of their perceived level of stress, and intake of food, alcohol, caffeine, and use of cigarettes. They will not be asked to change their diets, but will be asked to take either slow-release sodium chloride capsules, or matching placebo. They will also collect overnight urine samples every two weeks. This period will include the time of peak stress (e.g., April 15 of the tax accountants) and 4 weeks thereafter. Repeat blood samples will be taken at the time of peak stress. It is hypothesized that blood pressure will increase progressively as the level of occupational stress rises, and that this increase will be greatest in subjects with a positive family history of hypertension, and will be augmented by a high sodium intake.