Short‐term water deprivation attenuates the exercise pressor reflex in older female adults

Abstract

Older adults have reduced fluid intake and impaired body fluid and electrolyte regulation. Older female adults exhibit exaggerated exercise blood pressure (BP) responses, which is associated with an increased risk of adverse cardiovascular events. However, it is unclear if dysregulated body fluid homeostasis contributes to altered exercise BP responses in older female adults. We tested the hypothesis that short‐term water deprivation (WD) increases exercise BP responses in older female adults. Fifteen female adults (eight young [25 ± 6 years] and seven older [65 ± 6 years]) completed two experimental conditions in random crossover fashion; a euhydration control condition and a stepwise reduction in water intake over three days concluding with a 16‐hr WD period. During both trials, beat‐to‐beat BP (photoplethysmography) and heart rate (electrocardiogram) were continuously assessed during rest, handgrip exercise (30% MVC), and post‐exercise ischemia (metaboreflex isolation). At screening, older compared to young female adults had greater systolic and diastolic BP (p ≤ .02). Accelerometer‐assessed habitual physical activity was not different between groups (p = .65). Following WD, 24‐hr urine flow rate decreased, whereas thirst, urine specific gravity, and plasma osmolality increased (condition: p < .05 for all), but these WD‐induced changes were not different between age groups (interaction: p ≥ .31 for all). Resting systolic and diastolic BP values were higher in older compared to young adults (p < .01 for both), but were not different between experimental conditions (p ≥ .20). In contrast to our hypothesis, WD was associated with attenuated systolic BP responses during handgrip exercise (post hoc: p < .01) and post‐exercise ischemia (post hoc: p = .03) in older, but not young, female adults. These data suggest that reduced water intake‐induced challenges to body fluid homeostasis do not contribute to exaggerated exercise BP responses in post‐menopausal female adults.

Cardiorespiratory and autonomic adjustments to exercise with healthy ageing: considerations with extreme heat exposure and hydration

“…Basal pulmonary function can be altered by hyperthermia and/or dehydration independent of exercise, with hyperventilation occurring under significant heat strain (Travers et al., 2022). Mild whole‐body heating (∼0.4°C increased intestinal temperature) (Cui et al., 2021) and mild dehydration (∼0.5% body mass loss) (Watso et al., 2020) attenuate the blood pressure response to the exercise pressor reflex in older adults, which given the recent findings of Leahy et al., supports that a larger magnitude of physiological strain may be needed for the respiratory metaboreflex to influence these responses. To our knowledge, the impact of ageing on the interaction of extreme heat exposure and dehydration with the respiratory metaboreflex has not been studied.…”

“…Moreover, a recent report estimated that ∼71% of adults aged 51−70 years are not meeting one or more hydration criteria, suggesting that chronic insufficient hydration may also be an important factor. Indeed, there is some evidence indicating that moderate heat stress and/or dehydration modify the pressor response to exercise pressor reflex activation in older adults (Cui et al., 2021; Watso et al., 2020). More research is needed to better understand the integrative nature of these interactions in the context of older adults exposed to a warming climate.…”

Interplay of Race and Neighborhood Deprivation on Ambulatory Blood Pressure in Young Adults

“…Urine was collected for 24 hours before the study visit in a light-protected, sterile 3.5 L container. 26,43 Participants were instructed to record the time of their first void into a toilet on the day preceding the study visit, as well as their last void into the urine collection container on the day of the study visit. Urine flow rate was used to derive urinary ET-1 excretion and was calculated from urine volume and self-reported time the participant used the container in total.…”