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Biomedical subjects

Simon L Bacon

Publications and source records attributed to Simon L Bacon.

15 recordsLinked to original sources
PubMed2006

Asthma self-efficacy, high frequency heart rate variability, and airflow obstruction during negative affect in daily life.

BACKGROUND: Emotional stress has been considered an important asthma trigger for years, though the mechanisms by which stress may exacerbate asthma remain poorly understood. The stress-asthma morbidity association could occur through cognitive-behavioral pathways, such as decreased asthma self-efficacy and disorganized self-care, or through the more direct physiological effects of stress on autonomic (parasympathetic) nervous system activity. No study has examined how these two mechanisms may interact to contribute to greater airflow obstruction during emotional stress in daily life. This study investigated associations between peak expiratory flow rate (PEFR) and high frequency heart rate variability (HFHRV) during periods of negative affect and physical activity in daily life in patients with higher versus lower asthma self-efficacy scores. METHODS: Fifty-three patients with mild to moderate asthma completed the Asthma Self-Efficacy Scale (ASES) and underwent a 15 h ambulatory assessment of daytime HFHRV and PEFR, while completing self-report diaries of their physical activities and affect. RESULTS: In patients with lower asthma self-efficacy scores, increased levels of negative affect during daily life were associated with higher levels of HFHRV and decreased PEFR relative to patients with higher asthma self-efficacy scores. Increased levels of physical activity were associated with decreased levels of HFHRV irrespective of asthma self-efficacy scores. CONCLUSIONS: Findings suggest that lower asthma self-efficacy may be associated with increased parasympathetic activity and airflow obstruction during periods of negative affect during daily life.

Activities of Daily Living↗
PubMed2006

What is worse for asthma control and quality of life: depressive disorders, anxiety disorders, or both?

BACKGROUND: The high burden of asthma appears to be related to poor asthma control. Although previous studies have reported associations between depressive disorders (DDs) and anxiety disorders (ADs) and worse asthma control and quality of life, the relative impact of these disorders on asthma control and quality of life has not been explored. This study evaluated the relative impact of having a DD and/or AD on asthma control and quality of life. METHOD: Five hundred four consecutive adults with confirmed, physician-diagnosed asthma underwent a brief, structured psychiatric interview using the Primary Care Evaluation of Mental Disorders. Asthma control and asthma-related quality of life were assessed using the Asthma Control Questionnaire (ACQ) and the Asthma Quality of Life Questionnaire (AQLQ). All patients underwent standard spirometry. RESULTS: Thirty-one percent of patients (n = 157) met the diagnostic criteria for one or more psychiatric disorders (8% had DD only, 12% had AD only, and 11% had both). Analyses revealed independent effects for DDs on total ACQ scores (p < 0.01), and for DDs and ADs on total AQLQ scores and all four AQLQ subscales (p < 0.05). There were no interaction effects. CONCLUSIONS: Results suggest that DDs and ADs are associated with worse asthma-related quality of life, but only DDs are associated with worse asthma control. Interestingly, having both a DD and an AD did not confer additional risk for worse asthma control or quality of life. Physicians may want to consider the differential impact of negative mood states when assessing levels of asthma control and quality of life.

Adult↗
PubMed2005

Changes in plasma volume associated with mental stress ischemia in patients with coronary artery disease.

Psychological stress has been shown to trigger angina and myocardial ischemia in patients with coronary artery disease. However, the mechanisms by which stress may trigger cardiac events has yet to be fully elucidated. Twenty five patients underwent radionuclide ventriculography during a multiple stress challenge. Plasma volume was assessed during rest and at the end of the stress task. Flow-mediated dilatation was also measured. Controlling for endothelial function and medications, patients with ischemia had greater reductions in plasma volume than non-ischemic patients. Reduced plasma volume may be one mechanism by which mental stress may increase the risk for acute coronary events.

Aged↗
PubMed2005

Higher BMI is associated with worse asthma control and quality of life but not asthma severity.

Asthma and obesity tend to co-occur, but relatively few studies have linked obesity, measured using body mass index (BMI), to clinically relevant measures of asthma morbidity. This study assessed BMI in a Canadian sample of asthma outpatients, and evaluated associations between BMI and levels of asthma severity, asthma control, and asthma-related quality of life. A total of 382 adult asthma patients underwent demographic and medical history interviews on the day of their clinic visit. Patients' self-reported height and weight were used to calculate BMI (kg/m(2)). Asthma severity was classified according the GINA (2002) guidelines. Patients completed the Asthma Control (ACQ) and Asthma Quality of Life (AQLQ) Questionnaires and underwent standard pulmonary testing (spirometry). A total of 139 (36%) patients had a normal BMI; 149 (39%) patients were overweight; and 94 (25%) patients were obese. There was no relationship between BMI and asthma severity when controlling for age and sex. Patients with higher BMI scores had higher ACQ and lower AQLQ scores, independent of age, sex and asthma severity. Results identify higher BMI and obesity as potential behavioral factors related to worse asthma control and quality of life, but not asthma severity, and suggest important avenues for asthma management and control initiatives.

Adult↗
PubMed2005

Hemodynamic, hemostatic, and endothelial reactions to psychological and physical stress in coronary artery disease patients.

Episodes of psychological and physical stress may elicit thrombotic cardiac events, such as myocardial infarction. These events are triggered when there are concurrent hemodynamic, hemostatic, and endothelial abnormalities. Hemodynamic, hemostatic, and endothelial reactions of 72 (15 women, 57 men) coronary artery disease patients to psychological and physical stress were examined. Blood pressure, electrocardiography, and impedance cardiography were recorded during rest, mental arithmetic, and exercise. Blood was collected, via catheter, at rest and after each task. Mental arithmetic elicited increases in blood pressure, heart rate, cardiac output, and cardiac contractility, but no consistent changes in hemostatic and endothelial markers. In contrast, exercise, in addition to increasing blood pressure, heart rate, cardiac output, cardiac contractility, and lowering peripheral resistance, elicited increases in plasma viscosity, hematocrit, platelets, and tissue plasminogen activator together with a decrease in plasminogen activator inhibitor. This pattern of hemodynamic, hemostatic, and endothelial reactions suggests that acute psychological and physical stress influence the thrombotic system differently in these high risk patients. Future research is needed to investigate how these stress responses are prospectively related to acute cardiac events.

Acute Disease↗
PubMed2005

Are psychiatric disorders associated with worse asthma control and quality of life in asthma patients?

BACKGROUND: Achieving good asthma control has become the major goal of asthma treatment. Studies have reported a high rate of psychiatric disorders among asthma patients, though the impact of these disorders on asthma control and quality of life remains unexplored. This study evaluated the prevalence of psychiatric disorders in 406 adult asthma patients, and associations between psychiatric status, levels of asthma control, and asthma-related quality of life. METHODS: Consecutive asthma patients presenting to the asthma clinic underwent a brief, structured psychiatric interview, completed the Asthma Control Questionnaire (ACQ) and Asthma Quality of Life Questionnaire (AQLQ), and reported the frequency of bronchodilator use in the past week. All patients underwent standard pulmonary function testing. RESULTS: A total of 34% (n=136) of patients had one or more psychiatric diagnosis, including major depression (15%), minor depression (5%), dysthymia (4%), panic disorder (12%), generalized anxiety disorder (5%), and social phobia (4%). Though there were no differences in pulmonary function, patients with versus without psychiatric disorders had worse ACQ and AQLQ scores and reported greater bronchodilator use, independent age, sex and asthma severity. CONCLUSIONS: Results suggest that psychiatric disorders are prevalent among asthmatics and are associated with worse asthma control and quality of life. Physicians should be aware of the potential risk of poorer asthma control and functional impairment in this population.

Adult↗
PubMed2005

Effects of exercise and stress management training on markers of cardiovascular risk in patients with ischemic heart disease: a randomized controlled trial.

CONTEXT: Observational studies have shown that psychosocial factors are associated with increased risk for cardiovascular morbidity and mortality, but the effects of behavioral interventions on psychosocial and medical end points remain uncertain. OBJECTIVE: To determine the effect of 2 behavioral programs, aerobic exercise training and stress management training, with routine medical care on psychosocial functioning and markers of cardiovascular risk. DESIGN, SETTING, AND PATIENTS: Randomized controlled trial of 134 patients (92 male and 42 female; aged 40-84 years) with stable ischemic heart disease (IHD) and exercise-induced myocardial ischemia. Conducted from January 1999 to February 2003. INTERVENTIONS: Routine medical care (usual care); usual care plus supervised aerobic exercise training for 35 minutes 3 times per week for 16 weeks; usual care plus weekly 1.5-hour stress management training for 16 weeks. MAIN OUTCOME MEASURES: Self-reported measures of general distress (General Health Questionnaire [GHQ]) and depression (Beck Depression Inventory [BDI]); left ventricular ejection fraction (LVEF) and wall motion abnormalities (WMA); flow-mediated dilation; and cardiac autonomic control (heart rate variability during deep breathing and baroreflex sensitivity). RESULTS: Patients in the exercise and stress management groups had lower mean (SE) BDI scores (exercise: 8.2 [0.6]; stress management: 8.2 [0.6]) vs usual care (10.1 [0.6]; P = .02); reduced distress by GHQ scores (exercise: 56.3 [0.9]; stress management: 56.8 [0.9]) vs usual care (53.6 [0.9]; P = .02); and smaller reductions in LVEF during mental stress testing (exercise: -0.54% [0.44%]; stress management: -0.34% [0.45%]) vs usual care (-1.69% [0.46%]; P = .03). Exercise and stress management were associated with lower mean (SE) WMA rating scores (exercise: 0.20 [0.07]; stress management: 0.10 [0.07]) in a subset of patients with significant stress-induced WMA at baseline vs usual care (0.36 [0.07]; P = .02). Patients in the exercise and stress management groups had greater mean (SE) improvements in flow-mediated dilation (exercise: mean [SD], 5.6% [0.45%]; stress management: 5.2% [0.47%]) vs usual care patients (4.1% [0.48%]; P = .03). In a subgroup, those receiving stress management showed improved mean (SE) baroreflex sensitivity (8.2 [0.8] ms/mm Hg) vs usual care (5.1 [0.9] ms/mm Hg; P = .02) and significant increases in heart rate variability (193.7 [19.6] ms) vs usual care (132.1 [21.5] ms; P = .04). CONCLUSION: For patients with stable IHD, exercise and stress management training reduced emotional distress and improved markers of cardiovascular risk more than usual medical care alone.

Adult↗
PubMed2004

Association between exercise capacity and left ventricular geometry in overweight patients with mild systemic hypertension.

The purpose of this study was to determine the relation between left ventricular (LV) geometry and exercise capacity in unmedicated, hypertensive patients. Analysis of the data revealed peak oxygen consumption (ml kg(-1) min(-1)) for concentric hypertrophy (corrected mean +/- SE 23.5 +/- 1.2) was significantly less (F = 3.68, p <0.02) than the concentric remodeling (28.1 +/- 1.2) and normal (27.3 +/- 0.6) geometries. The LV geometric pattern was found to be associated with exercise capacity in unmedicated, hypertensive patients, such that patients with concentric hypertrophy showed reduced capacity.

Echocardiography↗
PubMed2004

Heart rate variability in coronary artery disease patients with and without panic disorder.

Panic disorder (PD) and coronary artery disease (CAD) often co-occur, and CAD patients with comorbid PD suffer greater cardiovascular morbidity and mortality relative to CAD patients without PD. However, the mechanisms underlying these associations are still unknown. Reduced heart rate variability (HRV), a non-invasive measure of cardiac autonomic modulation, is an important predictor of adverse cardiac events. Interestingly, reduced HRV has been observed in patients with panic-like anxiety and PD, as well as in various CAD populations. However, the extent to which HRV is altered in patients with both PD and CAD is unknown. This study evaluated HRV in 42 CAD patients with (n=20) and without (n=22) PD. Patients underwent 48-h electrocardiographic monitoring. Power spectral analysis of HRV indicated that CAD patients with PD exhibited significantly lower LF/HF ratios, which may reflect lower sympathetic modulation, compared with non-PD patients. Additionally, total power in PD patients was made up of a significantly higher proportion of HF power and a significantly lower proportion of VLF power than in non-PD patients. No other significant differences in HRV indices were observed. Results suggest that contrary to what has been observed in the majority of PD-only and CAD-only populations; patients with both PD and CAD appear to exhibit lower sympathetic modulation during ordinary daily life conditions. Though preliminary, these findings suggest that changes in HRV may not be the mechanism underlying greater cardiovascular morbidity and mortality among CAD patients with PD.

Activities of Daily Living↗
PubMed2004

Effects of daily stress on autonomic cardiac control in patients with coronary artery disease.

Emotional stress has been implicated in the development and progression of coronary artery disease, with 1 proposed causal pathway being changes in cardiac autonomic tone. One hundred thirty-five patients with coronary artery disease underwent 48 hours of ambulatory electrocardiographic monitoring and completed activity and mood diaries every 20 minutes while awake. Random-effects model analyses associated higher levels of negative emotions (e.g., anger, stress, sadness) with decreases in high- and low-frequency power, whereas higher levels of positive emotion were related to an increase in low-frequency power, independent of age, posture, and medications.

Coronary Artery Disease↗
PubMed2004

Are exercise stress tests appropriate for assessing myocardial ischemia in patients with major depressive disorder?

BACKGROUND: Major depressive disorder (MDD) disproportionately affects patients with coronary artery disease (CAD). Evidence of myocardial ischemia with electrocardiography (ECG) or single-photon-emission-computed-tomography (SPECT) assessments during exercise testing is an important determinant of CAD prognosis. However, many key symptoms of MDD, such as reduced interest in daily activities, lack of energy, and fatigue, may affect exercise performance and the detection of ischemia in patients with MDD. This study evaluated the extent to which MDD and depressive symptomatology moderate exercise test performance and compared the ability of ECG versus SPECT for detecting ischemia in 1367 consecutive patients who underwent exercise testing. METHODS: All patients underwent a brief, structured psychiatric interview (PRIME-MD) and completed the Beck Depression Inventory (BDI) on the day of their exercise (treadmill) test. RESULTS: A total of 183 patients (13%) met diagnostic criteria for MDD. Patients with MDD achieved a significantly lower percent of maximal predicted heart rate (%MPHR), exhibited lower peak exercise mets, and spent less time exercising compared with patients without MDD (all P values <.05). BDI scores were also negatively correlated with all 3 indices of exercise performance (all P values <.01). There were no differences in rates of SPECT ischemia in patients with MDD (40%) versus patients without MDD (45%; P =.23); however, rates of ECG ischemia were significantly lower (30%) in patients with MDD than in patients without MDD (48%; P <.0001). CONCLUSIONS: Results suggest that patients with CAD who have MDD, depressive symptomatology, or both exhibit poor exercise tolerance and performance and that ECG, as compared with SPECT, may not be as reliable in detecting ischemia in patients who are depressed.

Analysis of Variance↗
PubMed2004

Increases in lipids and immune cells in response to exercise and mental stress in patients with suspected coronary artery disease: effects of adjustment for shifts in plasma volume.

This study examined the role of shifts in plasma volume on lipid and immune reactions to stress. Lipid, immune, rheological, and cardiovascular reactions to exercise and mental stress in 51 patients with suspected coronary artery disease were determined. Blood pressure and heart rate were measured during and blood samples taken at the end of each rest and task. Lipids (total cholesterol, triglycerides, HDL, LDL) and immune cells (lymphocytes, monocytes, granulocytes) increased with exercise, whereas cholesterol, LDL, and lymphocytes increased with mental stress. Plasma volume decreased by 1 and 5% following mental and exercise stress, respectively. The task-induced increases in lipids were no longer statistically significant following adjustment for changes in plasma volume, whereas the increases in immune cell numbers survived such correction. This study provides evidence that, in coronary artery disease patients, exercise and mental stress-induced increases in lipids but not immune cells can be largely accounted for by shifts in plasma volume.

Adult↗
PubMed2004

Relationship between exercise systolic blood pressure and left ventricular geometry in overweight, mildly hypertensive patients.

OBJECTIVE: To examine the association between the graded exercise systolic blood pressure (SBP) response and left ventricular (LV) geometric structure in patients with untreated mild hypertension. PARTICIPANTS: The study included 80 sedentary, overweight patients (43 female and 37 male) with unmedicated high normal blood pressure or stage 1-2 hypertension. METHODS: An echocardiogram was used to determine LV mass and the relative wall thickness (RWT) in relation to the chamber dimension. Participants performed a maximal graded exercise test, and the SBP was recorded at workloads of 2, 4 and 6 metabolic equivalents and at peak exercise. Separate statistical models were used to determine the influence of LV mass indexed for height(2.7) (LVMIh) and RWT on submaximal exercise SBP and peak exercise SBP, controlling for resting SBP, age, gender, ethnicity and body mass index. RESULTS: A greater RWT was associated with a higher submaximal SBP level (P = 0.038). Neither LVMIh (P = 0.989) nor the interaction of RWT and LVMIh (P = 0.787) were related to the submaximal SBP. None of the main or interaction effects of RWT and LVMIh were associated with the peak exercise SBP level. CONCLUSION: Increases in RWT were associated with higher submaximal exercise SBP responses in a sample of overweight, unmedicated hypertensives. These results suggest that RWT is an important determinant of the association between cardiac mass and exercise SBP response.

Adult↗
PubMed2004

Effects of exercise, diet and weight loss on high blood pressure.

High blood pressure (BP) is a major health problem in the US, affecting more than 50 million people. Although high BP is among the most common reasons for outpatient visits, BP control is often inadequate. It is well established that BP can be lowered pharmacologically in hypertensive individuals; however, anti-hypertensive medications are not effective for everyone, and may be costly and result in adverse effects that impair quality of life and reduce adherence. Moreover, abnormalities associated with high BP, such as insulin resistance and hyperlipidaemia, may persist or may even be exacerbated by some anti-hypertensive medications. Consequently, there has been a great deal of interest in the development and application of behavioural interventions in the management of high BP. The main behavioural interventions that are recommended to reduce BP are exercise and the Dietary Approaches to Stop Hypertension (DASH) diet. Weight loss is also recommended for BP reduction in overweight individuals. Exercise alone is associated with reductions of approximately 3.5 and 2.0mm Hg in systolic (SBP) and diastolic blood pressure (DBP), respectively. Patients fed a DASH diet (a diet high in low-fat dairy products and fibre, including fruits and vegetables) had reductions in SBP and DBP of 5.5 and 3.0mm Hg, respectively, compared with those consuming a standard US diet. Reductions of approximately 8.5mm Hg SBP and 6.5mm Hg DBP accompany weight loss of 8 kg. In overweight hypertensive patients, a combined exercise and weight-loss intervention has been shown to decrease SBP and DBP by 12.5 and 7.9 mm Hg, respectively. There is evidence to suggest that these decreases in BP are associated with improvements in left ventricular structure and function, and peripheral vascular health. Both exercise training and weight loss have been shown to decrease left ventricular mass and wall thickness, reduce arterial stiffness and improve endothelial function. These data support the role of behavioural interventions in the treatment of patients with elevations in BP.

Behavior Therapy↗