Absence of sympathetic overactivity in Afro-Caribbean hypertensive subjects studied by heart rate variability

Abstract

Black hypertensives present a greater prevalence of left ventricular hypertrophy and an increased mortality compared to white hypertensives. Differences in sympathetic activity might contribute to explain these racial differences in hypertension. Nevertheless, previous laboratory studies did not show any increase of sympathetic activity direct to the heart in black subjects. The aim of the present study was to investigate the cardiac sympatho-vagal balance in black and white hypertensives analysing heart rate variability, during the entire 24 h. We analysed Holter recordings of 52 essential hypertensive patients, who had never received antihypertensive treatment, 26 of whom were black and 26 were white. Consecutive series of 300 beats, with 150 beats overlapped (approximately 600 series/day), were considered for the analysis in time and frequency domain. The mean 24-h value of the power of the low frequency spec-

Blacks and whites differ in responses, but not tolerance, to orthostatic stress

“…Resting middle-aged normotensive blacks were found to have lower HF and a higher LF/HF ratio than otherwise similar whites [10]; these data suggested lower parasympathetic and higher sympathetic activity in older blacks. When compared to whites, similar HF and a lower LF/HF ratio were seen in middleaged blacks with Stage I hypertension [6]. Likewise, resting HRV data from normotensive teenage blacks suggested higher parasympathetic and lower sympathetic activity compared to their white counterparts [29].…”

Cardiac autonomic control and the effects of age, race, and sex: The CARDIA study

“…In this study, the LF/HF ratio was greater in the blacks. In contrast, Guzzetti et al (Guzzetti et al, 2000) reported that 24-hour normalized LF power and the LF/HF ratio were lower in blacks compared to whites but the study was small (N = 52) and all subjects were untreated hypertensives. In another small study (N = 39) of males, the LF/HF ratio was lower and pNN50, an index of cardiac vagal modulation, was higher in blacks compared to whites (Urbina et al, 1998).…”

Does the white-coat effect in people of African and South Asian descent differ from that in White people of European origin? A systematic review and meta-analysis

“…Of the 10 studies we identified, eight met the inclusion criteria [13][14][15][16][17][18][19][20], four from the UK [14,[17][18][19] and four from the US [13,15,16,20]. We report the ethnic group terms used in the original publications.…”

“…Two study samples were collegebased [15,16], one comprised employees [20], one comprised hypertensive and normotensive patients [13], and the rest consisted of suspected hypertensive patients. As a marker of ethnicity, one study used country of origin [18] and one used self-report [15], while the others gave no information. In two UK studies, AfroCaribbeans and South Asians were significantly younger than Whites [14,19].…”