Sedentary behaviour in coronary heart disease and its effect on cardiometabolic risk markers and left ventricular function and structure

Abstract

The primary aim of the work included in this thesis was to investigate sedentary behaviour and its association with changes in left ventricular function and structure and cardiometabolic risk markers following a diagnosis of coronary heart disease. The systematic review and meta-analysis and the three acute experimental chapters included in this thesis sought to do this by examining postprandial glucose, insulin, total cholesterol, low density lipoprotein, high density lipoprotein cholesterol, triglycerides, blood pressure and measures of left ventricular function and structure. In study one, meta-analyses highlighted a small positive association between triglycerides and left ventricular mass index, as well as high density lipoprotein cholesterol with E/A ratio. Moreover, a small negative correlation was identified between both systolic and diastolic blood pressure with E/A ratio in healthy individuals or those with impaired cardiometabolic health (overweight, obesity or hypertension). Findings from the meta-analysis informed study two, which showed no association between cardiometabolic risk markers (including postprandial glucose, insulin, total cholesterol, low density lipoprotein, high density lipoprotein cholesterol, triglycerides, blood pressure) with left ventricular function and structure in individuals following a CHD event. However, sedentary behaviours and physical activity patterns predicted some of the variance in BMI, left ventricular function and structure. Here, shortened sitting bouts of less than 30 minutes in duration predicted some of the variance in BMI, posterior wall thickness during diastole and E' velocity. Number of sit to stand transitions also predicted variance in E wave, alongside moderate to vigorous intensity physical activity steps predicted variance in E/A ratio and A wave in study two. These findings suggest that both Time spent in sedentary behaviours, and frequent interruptions to prolonged sedentary behaviours may be important for cardiac remodelling post CHD diagnosis. Study four thus sought to investigate the effect of interrupting sedentary Time with 5-minute standing breaks and five-minute breaks of light intensity physical activity breaks, compared with prolonged sedentary behaviour. While there was no significant difference between conditions for cardiometabolic risk markers (postprandial glucose, insulin, total cholesterol, high density lipoprotein cholesterol or blood pressure), differences were observed between the conditions of standing breaks and light intensity physical activity breaks for E wave, A wave, left ventricular internal diameter at both systole and diastole, end systolic wall stress and left ventricular mass index. However, no difference to the prolonged sedentary behaviour condition was observed in this study. For the first Time, this thesis investigates sedentary behaviours in individuals following a CHD diagnosis in the UK, alongside its relationship with cardiometabolic risk markers and measures of left ventricular function and structure, in addition to examining the effects of frequently interrupting sitting Time with standing and light intensity physical activity breaks upon these markers. Chapter eight summarises the significance of the findings from the experimental studies included within this thesis, alongside highlighting future directions for research in this area of the field.

Date of Award	30 Aug 2024
Original language	English
Awarding Institution	University of Bedfordshire
Supervisor	Jo Richards (Supervisor), Lindsey Smith (Second supervisor) & Julia Fruer (Third supervisor)