Departments of Medicine and Pharmacology and the Cardiovascular Risk Factor Reduction Unit, University of Saskatchewan, Saskatoon.
People with hypertension are commonly warned to check with a physician before using a hot tub, but there is little literature on which to base this advice. We compared symptoms, heart rate, and systolic and diastolic blood pressure in response to 10 minutes of hot-tub immersion in a group of patients with treated hypertension and in a control group normotensive subjects.
We recruited 21 patients (18 men and 3 women aged 43-76 years) with stable, treated hypertension and 23 control subjects (14 men and 9 women aged 19-83 years) without hypertension. They were studied, in mid-afternoon, at a public facility. Systolic and diastolic blood pressure and heart rate were measured at baseline, during immersion in a hot tub at 40 degrees C and for 10 minutes after immersion. We asked each subject to report any symptoms.
None of the subjects reported dizziness, chest pain or palpitations. During immersion, systolic blood pressure fell in both groups, from a mean (and standard deviation [SD]) of 144 (17) mm Hg to 122 (18) mm Hg in the hypertensive group (p < 0.05) and from 130 (14) mm Hg to 110 (17) mm Hg in the control group (p < 0.05). It returned toward baseline within 10 minutes after the subjects left the hot tub. Diastolic blood pressure also fell, whereas heart rate was increased in both groups. The hypertensive group showed a slightly lower maximal increase in heart rate than the normotensive group (5 [SD 5] v. 13 [SD 10] beats/minute, p < 0.05).
Immersion in a hot tub for 10 minutes lowers blood pressure in subjects with treated hypertension, but no more than in normotensive control subjects. Spending 10 minutes in a hot tub should be safe for most treated hypertensive patients.