Abstract
PurposePrevalence of cardiovascular disease (CVD) is greater in South Asians (SAs) than White Europeans (WEs). Endothelial dysfunction and blunted forearm vasodilatation to environmental stressors have been implicated in CVD. We investigated whether these features are present in young SA men.MethodsIn 15 SA and 16 WE men (19–23 years), we compared changes in forearm blood flow, arterial blood pressure (ABP), forearm vascular conductance (FVC), heart rate, and electrodermal resistance (EDR; sweating) following release of arterial occlusion (reactive hyperaemia endothelium-dependent) and 5 single sounds at 5–10 min intervals (stressors).ResultsAll were normotensive. Peak reactive hyperaemia was smaller in SAs than WEs (FVC increase: 0.36 ± 0.038 vs 0.44 ± 0.038 units; P < 0.05). Furthermore, in WEs, mean FVC increased at 5, 15, and 20 s of each sound (vasodilatation), but increased at 5 s only in SAs, decreasing by 20 s (vasoconstriction). This reflected a smaller proportion of SAs showing forearm vasodilatation at 15 s (5/15 SAs vs 11/16 WEs: P < 0.01), the remainder showing vasoconstriction. Concomitantly, WEs showed greater bradycardia and EDR changes. Intra-class correlation analyses showed that all responses were highly reproducible over five sounds in both WEs and SAs. Moreover, sound-evoked changes in ABP and FVC were negatively correlated in each ethnicity (P < 0.01). However, WEs showed preponderance of forearm vasodilatation and depressor responses; SAs showed preponderance of vasoconstriction and pressor responses.ConclusionsEndothelium-dependent vasodilatation is blunted in young SA men. This could explain their impaired forearm vasodilatation and greater pressor responses to repeated environmental stressors, so predisposing SAs to hypertension and CVD.
Highlights
Communicated by Carsten Lundby.Population studies in the UK, Canada and USA indicate that South Asians (SAs) with ethnic roots in India, Pakistan, Bangladesh, Sri Lanka, or Nepal, have a 2–3-fold greater risk of death from all cardiovascular disease (CVD) than those of White European origin (WE; Gupta et al 2006; Rana et al 2014; Wild et al 2007)
Forearm blood flow (FBF) was recorded at 5, 15, and 20 s into each sound: 5 s was the earliest timepoint at which we could measure and gave us an index of the very early part of the response when arterial blood pressure (ABP) is rising; 15 s is the timepoint we have used before when ABP and skin vasoconstriction have reached their peak (Edwards et al 1998); a measurement at 20 s was included to indicate whether the forearm vascular response stabilised
There were no significant differences between the ethnic groups for anthropometric data and lifestyle variables except caffeine intake, which was greater in WEs (Table 1); it should be noted that all subjects refrained from caffeine intake for at least 24 h before the experiment
Summary
Communicated by Carsten Lundby.Population studies in the UK, Canada and USA indicate that South Asians (SAs) with ethnic roots in India, Pakistan, Bangladesh, Sri Lanka, or Nepal, have a 2–3-fold greater risk of death from all cardiovascular disease (CVD) than those of White European origin (WE; Gupta et al 2006; Rana et al 2014; Wild et al 2007). SA men and women (20–60 years) in the USA, who were non-diabetic and normotensive had higher plasma insulin and showed blunted brachial artery vasodilatation to insulin relative to age-matched WEs (Raji et al 2004). Non-diabetic, normotensive SA men (20–40 years) resident in the UK showed higher plasma insulin, smaller flow-mediated dilatation (FMD) and smaller tonic dilator influence of nitric oxide (NO) than WEs (Murphy et al 2007). These findings suggest that endothelial dilator function deteriorates at an earlier age in SA than WE men and may precede development of hypertension and diabetes
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