Slow breathing has unequal effects on prehypertensives from different ethnic/racial groups

Abstract

In this study, we investigated whether slow breathing reduces blood pressure (BP) in individuals at risk of developing hypertension and if slow breathing has the same effect on Caucasian, African, Arabian and Indian subjects. Also we assessed ethnic/racial differences in low frequency (LF) power and high frequency (HF) power of heart rate variability (HRV). A total of 40 Caucasian men from Ukraine, 39 West African men mostly from Nigeria, 38 Arabic men from Palestine and Israel and 41 South Asian men from India studying at V. N. Karazin Kharkiv National University were recruited in this study. The subjects were further classified into normotensive and prehypertensive groups. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), LF power, HF power of HRV were recorded at spontaneous breathing and at paced breathing of 10 and 6 breaths per minute. It was found that slowing respiratory rate to 6 breaths per minute reduces SBP in prehypertensive Caucasians, Arabs, Indians, but not in Africans. At 6 breaths per minute, natural logarithm of HF (LnHF) power indicating cardiovagal activity was less in normotensive Arabs than in Caucasians, Africans and Indians possibly suggesting an increased risk of developing hypertension; while prehypertensive Africans demonstrated LnHF power higher than Arabs and Indians. When covariates like age and body mass index (BMI) were considered, prehypertensive Africans demonstrated LnHF power higher than in Caucasians also. It is suggested that in prehypertensive Africans the control of autonomic nervous activity is reset to a higher level of parasympathetic outflow.