Reply from Paul J. Fadel

Abstract

I appreciate the Letter by Dr Akshay Pendyal (2020) regarding our recent publication in Experimental Physiology reporting an augmented resting beat-to-beat blood pressure (BP) variability in young non-Hispanic black men compared to white men (Young et al., 2020). We further observed that this enhanced BP variability was associated with greater fluctuations in systemic vascular resistance and reduced sympathetic baroreflex sensitivity. Notably, this heightened BP variability occurred despite a normal, and similar, resting BP between groups. We proposed that these swings in BP over time may contribute to the enhanced cardiovascular risk profile in black individuals. Dr Pendyal raises an important and timely point about a potential underlying factor that may contribute to the observed differences, namely the unequal societal conditions and enhanced environmental stress (i.e. racism) that many black individuals encounter on a regular basis, particularly black men. We completely agree with Dr Pendyal and our intention was not to disregard or downplay this factor as an underlying contributor. However, we are physiologists by training and our study was designed to investigate neural cardiovascular mechanisms as presented in the paper, and not psycho-social factors. Thus, the intent was not to overlook this factor, but with no measures made in our volunteer participants to directly assess and speak to these factors, we were careful not to comment. In fact, quantifying such experiences can be challenging, particularly considering the varying backgrounds, societal conditions and exposures to enhanced environmental stress (i.e. cultural, socioeconomic, and psychosocial factors) among our participants. As such, we cannot comment in any meaningful way on these factors as we can for measures of endothelium-dependent vasodilatation and sympathetically mediated vasoconstriction. Nevertheless, we recognize that differences in environmental factors between black and white individuals, and in the case of our study men, undoubtedly impact cardiovascular physiology and in no way are we pinning these differences solely on genetics, per Dr Pendyal's concern. This is just not a factor we have reported on in our studies as assessing these environmental stress factors is not trivial and requires a dedicated approach in and of itself. Similarly, papers on socio-economic and cultural factors in society rarely mention physiological mechanisms. In short, we agree with Dr Pendyal and in no way were we suggesting these were ‘purely’ intrinsic physiological differences between black and white men. The enhanced environmental stressors that most black individuals have to deal with on a regular basis should not be overlooked as contributory factors for the heightened cardiovascular risk in this population (Brownlow et al., 2019; Clark, Anderson, Clark, & Williams, 1999; Frierson, Howard, DeFina, Powell-Wiley, & Willis, 2013). Clearly these interactions are important and are worthy of future investigation, particularly studies using interdisciplinary approaches merging physiological and psychosocial factors. We thank Dr Pendyal for the reminder of the complexities of studying racial differences and the importance of considering the stress of racism and socioeconomic deprivation on cardiovascular physiology in black individuals. None declared.