Blood pressure status and post-exercise hypotension: an example of a spurious correlation in hypertension research?

Abstract

A single bout of exercise lowers blood pressure (BP) for up to 24 h afterwards. The magnitude of this post-exercise hypotension (PEH) has been reported to be correlated most strongly to pre-exercise BP, and this apparent relationship has influenced position statements about the value of exercise in arterial hypertension. Nevertheless, this correlation could be adversely affected by mathematical coupling and regression-to-the-mean artefacts. Therefore, we aimed to examine the degree to which BP status moderates PEH while, for the first time, controlling for these statistical artefacts. A total of 32 participants, with preexercise mean arterial pressures of 65-110 mm Hg, cycled for 30 min at 70% peak oxygen uptake. Systolic BP and diastolic BP were measured (Portapres) before exercise and for 20 min after exercise. Changes in BP were regressed against pre-exercise values, and against the mean of pre-and post-exercise BP, among other indices that are also known not to be prone to artefacts. Correlations between pre-exercise BP and the exercisemediated reductions were typical of those previously reported (r ¼ 0.37-0.62, Po0.05), but not large enough to rule out spuriousness (P40.05). Artefact-free indices of BP status (pre-and post-exercise mean as well as an earlier independent measurement) did not correlate with reductions in BP (P40.05), which were moderated more by peak oxygen uptake and time of day (Po0.05). These data indicate that, if statistical artefacts are not controlled for, the influence of BP status on the degree of PEH can be spuriously exaggerated to the extent that other more important moderators of BP change are masked.

True and false interindividual differences in the physiological response to an intervention

“…, ; Atkinson & Taylor, ; Taylor et al . ; Atkinson, ). Therefore, her study is perceived to have impact on the treatment of people with existing hypertension.…”

Effect of 12 weeks of resistance exercise on post-exercise hypotension in stage 1 hypertensive individuals

“…5,12 PEH has been documented to be greater in hypertensive than normotensive individuals 5 and its magnitude seems to be dependent on resting/pre-exercise BP values. 13,14 As chronic exercise induces resting BP reduction, it is possible that the magnitude of PEH can be reduced due to adaptation to exercise. 5,15 This issue has been poorly investigated, especially with regards to resistance exercise, 16 and has not been evaluated in hypertensive individuals submitted to RET.…”

Inter-individual variability in the improvement of physiological risk factors for disease: gene polymorphisms or simply regression to the mean?

“…As illustrated recently in the context of the BP‐lowering effects of exercise (Taylor et al 2010), regression‐to‐the‐mean can compromise the interpretation of individual differences in physiological responses to exercise, or indeed any intervention. Because of inherent measurement error in phenotypes such as BP, individuals who are initially found to lie at the extreme ends of a population distribution are likely to record, at follow‐up, values that are closer to the population mean.…”

“…The fraction of the variability in responses explained by polymorphisms was reported to be small (<5%). Nevertheless, we wonder whether the regression‐to‐the‐mean artifact might have ‘swamped’ this analysis, as it did in our analysis of other factors influencing the BP response to exercise (Taylor et al 2010). It is interesting that the individuals with the A/A genotype showed the largest reduction in BMI, yet these subjects also showed the highest mean initial BMI.…”