Influence of hospitalization and placebo therapy on blood pressure and sympathetic function in essential hypertension.

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Abstract
The decline in blood pressure (BP) in essential hypertensives following hospitalization may result from: regression toward the mean; reduction of anxiety as patients habituate to a new environment; the placebo effect of medication; and an independent effect of hospitalization itself. A randomized crossover study of 12 essential hypertensives demonstrated a fall in supine blood pressure from 165.0/97.9 .+-. 2.3/1.1 mm Hg to 154.3/89.6 .+-. 2.7/1.1 mm Hg (P < 0.005) due to hospitalization. A similar reduction in BP from 164.9/99.5 .+-. 8.4/4.1 mm Hg to 151.9/93.4 .+-. 4.5/1.9 mm Hg (P < 0.005) resulted from regression toward the mean and habituation during the study period. Urinary catecholamines fell from 68.7 .+-. 5.0 to 55.1 .+-. 4.3 .mu.g/g creatinine per 24 h (P < 0.05) due to hospitalization and from 56.1 .+-. 5.4 to 49.7 .+-. 4.3 .mu.g/g creatinine per 24 h (P < 0.05) with time. Although placebo therapy tended to reduce BP, it failed to do so significantly. When expressed as a percentage of the individual''s overall mean, urinary catecholamine excretion fell from 110.5% .+-. 3.7% to 89.5% .+-. 3.7% (P < 0.001) during hospitalization and from 105.8% .+-. 3.9% to 94.2% .+-. 3.9% (P < 0.05) during the outpatient period. Blood pressure and sympathetic activity rapidly returned to prehospitalization values on discharge. These factors may confound the analysis of drug effects on BP and sympathetic activity in essential hypertensives following admission to hospital.