Ageing, Blood Pressure, Sleep and Exercise - Mechanisms of Acute and Long Term Effects

Abstract

Ageing is a natural process that is accompanied by several structural and functional changes leading to an increase in blood pressure (BP), reduced sleep, a decrease in pulmonary function, and reduced exercise capacity. Physical exercise is an effective strategy to improve many of the variables that are known to deteriorate with advancing age, including BP, sleep and exercise capacity. However, whether sleep is disrupted after an acute bout of evening exercise, thus potentially increasing the risk to develop hypertension, is currently unknown and needs to be tested. Further, due to an age-associated increase in prevalence of conditions affecting the musculoskeletal system, alternative strategies with similar beneficial effects as physical exercise are needed. Two such strategies could be respiratory muscle endurance training (RMET) and intermittent hypoxia (IH). The main goals of this thesis were twofold: to determine whether an acute bout of evening exercise compromises sleep and to test the acute and long term effects of RMET with and without IH on BP, sleep, pulmonary function and exercise capacity in healthy normotensive and prehypertensive elderly. To do so, we first performed a systematic review and meta-analysis including all studies that investigated the effects of a single session of evening exercise on sleep compared to a no-exercise control condition. We found that evening exercise does not compromise sleep (in fact rather the opposite), except for late-night intense exercise ending ≤ 1 h before bedtime. Second, we recruited 14 prehypertensive but otherwise healthy elderly to test whether one session of intermittent RMET alone and in combination with IH would result in a transient decrease in BP and improve sleep. Contrary to our expectation, there was no decrease in BP after one acute session of intermittent RMET, and the effects on sleep were inconclusive. Further, the addition of IH did not have any additional effects on sleep and BP when compared to an acute bout of RMET alone. Finally, we recruited 24 healthy elderly to evaluate whether long term RMET, without the addition of IH, would result in lower resting BP, better sleep, improved pulmonary function and increased exercise performance. Participants in the RMET group performed on average 21 sessions of normocapnic hyperpnea over the course of 4-5 weeks whereas participants in the placebo group inhaled 20 times a lactose powder from a mock asthma inhaler. We found that only participants in the training group improved respiratory muscle endurance and whole body endurance performance. BP, sleep and other indices of pulmonary function were not improved after RMET compared to placebo. We conclude that RMET could be used as an adjunct to whole body exercise to improve respiratory and whole body exercise performance, although it is questionable whether this has practical applications given the absence of improvements in other health-related parameters that are known to worsen with age.