Mental Stress In Healthy Subjects Research Articles

Validation of the Apple Watch for Heart Rate Variability Measurements during Relax and Mental Stress in Healthy Subjects.

Heart rate variability (HRV) analysis is a noninvasive tool widely used to assess autonomic nervous system state. The market for wearable devices that measure the heart rate has grown exponentially, as well as their potential use for healthcare and wellbeing applications. Still, there is a lack of validation of these devices. In particular, this work aims to validate the Apple Watch in terms of HRV derived from the RR interval series provided by the device, both in temporal (HRM (mean heart rate), SDNN, RMSSD and pNN50) and frequency (low and high frequency powers, LF and HF) domain. For this purpose, a database of 20 healthy volunteers subjected to relax and a mild cognitive stress was used. First, RR interval series provided by Apple Watch were validated using as reference the RR interval series provided by a Polar H7 using Bland-Altman plots and reliability and agreement coefficients. Then, HRV parameters derived from both RR interval series were compared and their ability to identify autonomic nervous system (ANS) response to mild cognitive stress was studied. Apple Watch measurements presented very good reliability and agreement (>0.9). RR interval series provided by Apple Watch contain gaps due to missing RR interval values (on average, 5 gaps per recording, lasting 6.5 s per gap). Temporal HRV indices were not significantly affected by the gaps. However, they produced a significant decrease in the LF and HF power. Despite these differences, HRV indices derived from the Apple Watch RR interval series were able to reflect changes induced by a mild mental stress, showing a significant decrease of HF power as well as RMSSD in stress with respect to relax, suggesting the potential use of HRV measurements derived from Apple Watch for stress monitoring.

Sensory trigeminal ULF-TENS stimulation reduces HRV response to experimentally induced arithmetic stress: A randomized clinical trial

Ultra Low Frequency Transcutaneous Electric Nervous Stimulation (ULF-TENS) is extensively used for pain relief and for the diagnosis and treatment of temporomandibular disorders (TMD). In addition to its local effects, ULF-TENS acts on the autonomic nervous system (ANS), with particular reference to the periaqueductal gray (PAG), promoting the release of endogenous opioids and modulating descending pain systems. It has been suggested that the PAG participates in the coupling between the emotional stimulus and the appropriate behavioral autonomic response. This function is successfully investigated by HRV. Therefore, our goal is to investigate the effects of trigeminal ULF-TENS stimulation on autonomic behavior in terms of HRV and respiratory parameters during an experimentally-induced arithmetic stress test in healthy subjects.Thirty healthy women between 25 and 35years of age were enrolled and randomly assigned to either the control (TENS stimulation off) or test group (TENS stimulation on). Heart (HR, LF, HF, LF/HF ratio, DET, RMSSD, PNN50, RR) and respiratory (BR) rate were evaluated under basal, T1 (TENS off/on), and stress (mathematical task) conditions. Results showed that HRV parameters and BR significantly changed during the arithmetic stress paradigm (p<0.01). Independently of stress conditions, TENS and control group could be discriminated only by non-linear HRV data, namely RR and DET (p=0.038 and p=0.027, respectively). During the arithmetic task, LF/HF ratio was the most sensitive parameter to discriminate between groups (p=0.019).Our data suggest that trigeminal sensory ULF-TENS reduces the autonomic response in terms of HRV and BR during acute mental stress in healthy subjects. Future directions of our work aim at applying the HRV and BR analysis, with and without TENS stimulation, to individuals with dysfunctional ANS among those with TMD.

Entropy Analysis of RR and QT Interval Variability during Orthostatic and Mental Stress in Healthy Subjects

Autonomic activity affects beat-to-beat variability of heart rate and QT interval. The aim of this study was to explore whether entropy measures are suitable to detect changes in neural outflow to the heart elicited by two different stress paradigms. We recorded short-term ECG in 11 normal subjects during an experimental protocol that involved head-up tilt and mental arithmetic stress and computed sample entropy, cross-sample entropy and causal interactions based on conditional entropy from RR and QT interval time series. Head-up tilt resulted in a significant reduction in sample entropy of RR intervals and cross-sample entropy, while mental arithmetic stress resulted in a significant reduction in coupling directed from RR to QT. In conclusion, measures of entropy are suitable to detect changes in neural outflow to the heart and decoupling of repolarisation variability from heart rate variability elicited by orthostatic or mental arithmetic stress.

Hemodynamic mechanisms of the attenuated blood pressure response to mental stress after a single bout of maximal dynamic exercise in healthy subjects

To determine the hemodynamic mechanisms responsible for the attenuated blood pressure response to mental stress after exercise, 26 healthy sedentary individuals (age 29 ± 8 years) underwent the Stroop color-word test before and 60 min after a bout of maximal dynamic exercise on a treadmill. A subgroup (N = 11) underwent a time-control experiment without exercise. Blood pressure was continuously and noninvasively recorded by infrared finger photoplethysmography. Stroke volume was derived from pressure signals, and cardiac output and peripheral vascular resistance were calculated. Perceived mental stress scores were comparable between mental stress tests both in the exercise (P = 0.96) and control (P = 0.24) experiments. After exercise, the systolic blood pressure response to mental stress was attenuated (pre: 10 ± 13 vs post: 6 ± 7 mmHg; P < 0.01) along with lower values of systolic blood pressure (pre: 129 ± 3 vs post: 125 ± 3 mmHg; P < 0.05), stroke volume (pre: 89.4 ± 3.5 vs post: 76.8 ± 3.8 mL; P < 0.05), and cardiac output (pre: 7.00 ± 0.30 vs post: 6.51 ± 0.36 L/min; P < 0.05). Except for heart rate, the hemodynamic responses and the mean values during the two mental stress tests in the control experiment were similar (P > 0.05). In conclusion, a single bout of maximal dynamic exercise attenuates the blood pressure response to mental stress in healthy subjects, along with lower stroke volume and cardiac output, denoting an acute modulatory action of exercise on the central hemodynamic response to mental stress.

Autonomic and muscular responses and recovery to one-hour laboratory mental stress in healthy subjects

BackgroundStress is a risk factor for musculoskeletal pain. We wanted to explore stress related physiology in healthy subjects in order to gain insight into mechanisms of pain development which may relate to the pathophysiology of musculoskeletal pain disorders.MethodsContinuous blood pressure, heart rate, finger skin blood flow, respiration, surface electromyography together with perception of pain, fatigue and tension were recorded on 35 healthy women and 9 healthy men before, during a 60 minute period with task-related low-grade mental stress, and in the following 30 minute rest period.ResultsSubjects responded physiologically to the stressful task with an increase in trapezius and frontalis muscle activity, increased blood pressure, respiration frequency and heart rate together with reduced finger skin blood flow. The blood pressure response and the finger skin blood flow response did not recover to baseline values during the 30-minute rest period, whereas respiration frequency, heart rate, and surface electromyography of the trapezius and frontalis muscles recovered to baseline within 10 minutes after the stressful task. Sixty-eight percent responded subjectively with pain development and 64% reported at least 30% increase in pain. Reduced recovery of the blood pressure was weakly correlated to fatigue development during stress, but was not correlated to pain or tension.ConclusionBased on a lack of recovery of the blood pressure and the acral finger skin blood flow response to mental stress we conclude that these responses are more protracted than other physiological stress responses.

Electrophysiologic effects of mental stress in healthy subjects: a comparison with epinephrine infusion

Mental stress has been associated with serious cardiac arrhythmias, including ventricular tachycardia and ventricular fibrillation. The purpose of this study was to assess cardiac electrophysiologic effects of mental stress and compare them with those of epinephrine infusion. Ten healthy male volunteers participated. Electrophysiologic and hemodynamic variables were measured at baseline, during mental stress produced by Stroop’s color word conflict test and during epinephrine infusion at 2 rates (0.025 μmol/kg/min and 0.3 μmol/kg/min). Mental stress produced significant effects on the electrophysiologic properties of the heart with shortening of all measured electrophysiologic variables except atrial, most markedly those of the sinus and the atrioventricular nodes. The effects on the right ventricular myocardium and the His-Purkinje conduction system were less pronounced. During infusion of epinephrine, corresponding effects could only be reproduced at a much higher plasma level. Circulating epinephrine apparently plays a minor role as a mediator of mental stress effects on the heart.

Gender but not age affects cardiovascular performance during mental stress in healthy subjects 20–93 years old

Gender but not age affects cardiovascular performance during mental stress in healthy subjects 20–93 years old

Impairment of the nitric oxide–mediated vasodilator response to mental stress in hypertensive but not in hypercholesterolemic patients

Objectives. This study investigated whether mental stress–induced vasodilation mediated by endothelium-derived nitric oxide (NO) is defective in conditions with endothelial dysfunction, such as hypertension and hypercholesterolemia.Background. Vascular release of NO modulates the vasodilator response to mental stress in healthy subjects. Previous studies have shown that hypertensive and hypercholesterolemic patients have impaired endothelium-dependent vasodilation to pharmacologic agents due to decreased NO activity. However, whether this abnormality also operates in response to physiologic stimuli such as mental stress has not been defined.Methods. Forearm blood flow responses (plethysmography) to mental stress were compared in 12 normal subjects, 12 hypertensive patients and 10 hypercholesterolemic patients before and during NO synthesis inhibition with NG-monomethyl-l-arginine (4 μmol/min). Vascular responses to acetylcholine (7.5, 15 and 30 μg/min), an endothelium-dependent vasodilator, and sodium nitroprusside (0.8, 1.6 and 3.2 μg/min), an exogenous NO donor, were also assessed in each group.Results. During saline the vasodilator response to mental stress was significantly blunted in hypertensive (37 ± 11%; p = 0.01) but not in hypercholesterolemic (85 ± 21%; p = 0.78) patients compared with controls (93 ± 15%). NG-Monomethyl-l-arginine administration significantly blunted mental stress–induced vasodilation in healthy subjects (p = 0.004 vs. saline) and hypercholesterolemic patients (p = 0.03 vs. saline), but not in hypertensive patients (p = 0.69 vs. saline). The vasodilator effect of the highest dose of acetylcholine was similarly blunted in hypertensive (215 ± 44%; p = 0.02) and hypercholesterolemic (172 ± 71%; p = 0.02) patients compared with controls (364 ± 34), whereas the vasorelaxing response to sodium nitroprusside was similar in the three groups.Conclusions. Hypertensive but not hypercholesterolemic patients have impaired NO-dependent vasodilation during mental stress. These findings may be accounted for by different mechanisms underlying endothelial dysfunction in these two conditions and might explain an increased susceptibility of hypertensive patients to vascular damage over repeated exposure to stressful situations.

Potent mental stress and insulin absorption in normal subjects.

Effects of mental stress (a 20-min modified Stroop's color-word conflict test; CWT) on the absorption of 125I-labeled soluble human insulin (10 U s.c. in the thigh 60 min before CWT) and on subcutaneous adipose tissue blood flow (ATBF; 133Xe clearance); heart rate (HR); arterial blood pressure (BP); and arterial levels of epinephrine (Epi), norepinephrine (NE), and glycerol were studied in 11 healthy subjects. Insulin absorption was measured as elimination of radioactivity (external gamma-counting) and as appearance of plasma immunoreactive insulin (IRI). The glucose-clamp technique was used to maintain normoglycemia. Identical measurements were performed during a control day without CWT. HR and mean BP increased markedly (35 +/- 5 beats/min and 30 +/- 3 mmHg) during CWT despite only minor elevations in plasma catecholamines. Thus, arterial plasma Epi rose from 0.18 +/- 0.03 to 0.82 +/- 0.17 nM (P less than .01) and NE from 0.94 +/- 0.09 to 1.69 +/- 0.18 nM (P less than .001). ATBF showed a biphasic response, with a 100% elevation during CWT followed by a decrease and a second peak of similar magnitude approximately 0.5 to 1 h after CWT. Blood glycerol was approximately doubled during CWT and remained elevated during recovery. Despite these changes, insulin absorption was unaltered during and after stress. Thus, elimination rates of 125I, plasma IRI levels, and amounts of glucose needed to maintain normoglycemia were all similar during the stress and control days. These results suggest that absorption of soluble insulin from subcutaneous injection sites in the thigh is unaltered during potent mental stress in healthy subjects despite a considerable and prolonged increase in ATBF.