Interventions for lowering cardiovascular disease risk markers in chronic obstructive pulmonary disease patients and apparently healthy smokers

Abstract

Cardiovascular disease (CVD) is a leading cause of death worldwide. Disease prevention is a fundamental element in tackling CVD, which includes lifestyle modification. Physical activity (PA) is a beneficial modifiable risk factor for individual health. Higher levels of PA are associated with a lower risk of CVD and all-cause mortality. While CVD prevention is essential for every individual, it is more critical for those who are at higher CVD risk such as smokers and people with chronic obstructive pulmonary disease (COPD). This thesis consists of three studies and one study protocol designed to tackle CVD risk. First, using two, 2-day conditions (control, exercise) in a randomised crossover design, this thesis examined the effects of acute running exercise for attenuating postprandial lipaemia (PPL) and other CVD risk markers in 12 healthy young male smokers and 12 matched male non-smokers. The findings revealed that C-reactive protein (CRP) and fasted triacylglycerol and low density lipoprotein cholesterol concentrations were significantly higher in smokers than non-smokers while high density lipoprotein cholesterol concentrations were lower in smokers than non-smokers. The postprandial lipaemic response to a high-fat meal was higher in smokers than non-smokers and was attenuated to a similar extent the day after exercise in smokers and non-smokers. Exercise also lowered plasma insulin and resting arterial blood pressure responses and increased CRP concentrations in smokers and non-smokers. C-reactive protein concentrations were increased to a similar extent in both groups in response to acute exercise and C-reactive protein concentrations were also elevated in control conditions in smokers. These findings highlight the ability of an acute bout of exercise to augment the postprandial metabolic health of cigarette smokers and non-smokers. Second, a robust protocol that accounts for the control condition and replicates both control and intervention conditions was used to test the reproducibility and true interindividual variability of PPL, arterial stiffness, systolic and diastolic blood pressure responses to acute exercise and high-fat meals. This study revealed promising results where PPL and arterial stiffness responses to acute exercise were reproducible in some of the healthy young male participants, and most participants replicated their responses after the two exercise conditions. Although the findings revealed that acute exercise with high-fat meal ingestion attenuated next day blood pressure, the blood pressure responses showed a large participant variability demonstrated by graph visualisation. Further research with a larger sample size is needed to expand knowledge about the reproducibility and individual variability of CVD risk marker responses to acute exercise. Third, a secondary analysis was conducted on a dataset from four studies to investigate the effectiveness of home based and centre based pulmonary rehabilitation (PR) in people with COPD by stratifying responders (change in PA ≥ 1000 steps/day or change in incremental shuttle walk test (ISWT) performance ≥ 40 m or both) and non-responders (PA change ≤ 1000 steps/day and ISWT change ≤39 m) for each intervention. The baseline characteristics for each response group were compared and tested (using linear regression) as predictors for the improvements in PA. The study revealed that centred-based PR was more effective than home-based PR and usual care in increasing the proportion of responders (PA ≥ 1000 steps/day or ISWT ≥ 40 m or both) and group average ISWT performance. Baseline ISWT performance was shown to predict the change in PA level after PR. People with COPD who had better ISWT performance at baseline were more likely to improve their PA level after PR. Fourth, a robust randomised control study protocol was designed to tackle CVD risk in peo