Vascular Response During Mental Stress in Sedentary and Physically Active Patients With Obstructive Sleep Apnea

Sedentary behaviour is associated with heightened cardiovascular, inflammatory and cortisol reactivity to acute psychological stress

BACKGROUND

Sedentary behaviour is a risk factor for cardiovascular disease (CVD), but the underlying mechanisms remain unclear. Exaggerated psychobiological responses to acute psychological stress increase CVD risk. Sedentary behaviour is associated with characteristics that can predict large psychobiological stress response patterns (e.g., elevated resting blood pressure and systemic inflammation), but it is currently unknown whether sedentary behaviour and stress reactivity are directly linked. The aim of this study was to examine associations between device-assessed sedentary behaviour and measures of stress reactivity.

METHODS

Sixty-one healthy adults wore an activPAL (thigh) and ActiGraph (wrist) for seven days to measure habitual levels of sedentary behaviour (mean ± SD = 9.96 ± 1.48 h/day) and moderate-to-vigorous physical activity (mean ± SD = 101.82 ± 42.92 min/day). Participants then underwent stress reactivity testing, where beat-to-beat cardiovascular (e.g., blood pressure, total peripheral resistance), inflammatory (plasma interleukin-6, leukocytes) and salivary cortisol measurements were taken in response to an 8-minute socially evaluative Paced Auditory Serial Addition Test.

RESULTS

Higher volumes of daily sedentary behaviour were associated with larger stress responses for diastolic blood pressure (Β=1.264, 95%CI=0.537-1.990, p = .005), total peripheral resistance (Β=40.563, 95%CI=19.310-61.812, p < .001), interleukin-6 (Β=0.219, 95%CI=0.109-0.329, p < .001) and cortisol (Β=1.844, 95%CI=1.139-2.549, p < .001). These findings emerged independent of a priori determined covariates, including daily levels of moderate-to-vigorous physical activity and adiposity.

DISCUSSION

Exaggerated stress reactivity is characteristic of high sedentary behaviour and could be a novel mechanism linking sedentary behaviour with CVD. Future work should examine the impact of reducing sedentary behaviour on measures of stress reactivity, as this may have clinical relevance for preventing CVD.

Effects of exercise training on brain metabolism and cognitive functioning in sleep apnea

Impaired glucose metabolism reflects neuronal/synaptic dysfunction and cognitive function decline in patients with obstructive sleep apnea (OSA). The study investigated the extent to which exercise training (ET) improves cerebral metabolic glucose rate (CMRgl) and cognitive function in patients with OSA. Patients with moderate to severe OSA were randomly assigned to ET (3 times/week, n = 23) or no intervention (control, n = 24). Echocardiography and apolipoprotein ε4 (APOEε4) genotyping were obtained at baseline. Both groups underwent cardiopulmonary exercise testing, polysomnography, cognitive tests, brain magnetic resonance imaging, and ¹⁸F-fluoro-2-deoxy-d-Glucose positron emission tomography (¹⁸FDG-PET) at baseline and study end. Compared with control, exercise-trained group had improved exercise capacity, decreased apnea–hypopnea index (AHI), oxygen desaturation and arousal index; increased attention/executive functioning, increased CMRgl in the right frontal lobe (P < 0.05). After ET an inverse relationships occurred between CMRgl and obstructive AHI (r = − 0.43, P < 0.05) and apnea arousal index (r = − 0.53, P < 0.05), and between the changes in CMRgl and changes in mean O₂ saturation during sleep and non-rapid eye movement sleep (r = − 0.43, P < 0.05), desaturation during arousal (r = − 0.44, P < 0.05), and time to attention function testing (r = − 0.46, P < 0.05). ET improves OSA severity and CMRg in the frontal lobe, which helps explain the improvement in attention/executive functioning. Our study provides promising data that reinforce the growing idea that ET may be a valuable tool to prevent hypoxia associated with decreased brain metabolism and cognitive functioning in patients with moderate to severe OSA.

Trial registration: NCT02289625 (13/11/2014).