Abstract
Background
Resistant hypertension is a special phenotype within hypertension which may remain uncontrolled despite pharmacological management. Adults with resistant hypertension have increased risk of cardiovascular mortality and morbidity. Further, resistant hypertension has a bidirectional relationship with obstructive sleep apnoea and the two compound each other. International hypertension guidelines recommend exercise as a therapeutic modality to manage hypertension but studies that have investigated the effectiveness of exercise in the management of resistant hypertension are limited and have not previously been undertaken on a New Zealand population.
Aim
The main aim of the thesis was to investigate the 24 hour blood pressure change in response to an exercise programme in individuals diagnosed with true resistant hypertension and at risk of obstructive sleep apnoea. The secondary aims were firstly, to provide evidence for the effectiveness of blood pressure change in response to exercise in cohorts with resistant hypertension; secondly, to determine the prevalence of true resistant hypertension in individuals diagnosed with resistant hypertension and investigate the association of resistant hypertension with obstructive sleep apnoea; and thirdly, for individuals living with resistant hypertension, to explore their perception of exercise as a therapeutic modality for their condition.
Methods
This mixed-method thesis includes quantitative and qualitative methodologies. A narrative review was undertaken to explore the potential role of exercise as a therapeutic modality to manage blood pressure in hypertension. The narrative review lead to the investigation of effectiveness of physical activity and exercise in blood pressure management in resistant hypertension in a systematic review. The descriptive observational study on prevalence of true resistant hypertension and association with obstructive sleep apnoea risk was followed by a single group pre- post-test trial. The qualitative study with individuals living with resistant hypertension was conducted as a standalone study with an inductive approach with thematic analysis.
Results
The narrative review showed that the current guidelines recommended physical activity and exercise as a therapeutic modality in management of hypertension. The systematic review confirmed that physical activity (mean differences; systolic -9.88 mmHg, 95% CI: -17.62 to -2.14/ diastolic -6.24 mmHg, 95% CI: -12.65 to 0.17), in particular aerobic exercise (mean differences; systolic -12.06 mmHg, 95% CI: -21.14 to -2.96 / diastolic -8.19 mmHg, 95% CI: -14.83 to -1.55) was clinically effective in reducing blood pressure in resistant hypertension when the mean differences of experimental and controlled groups were considered. A clinically meaningful blood pressure reduction in response to exercise was identified in pre and post-test measurements (systolic -10.14 mmHg, 95% CI: -17.04 to - 3.24 / diastolic -3.80 mmHg, 95% CI: 5.95 to 1.65) for experimental groups in published randomised control trials. The observational study reported that 22 of the 25 participating adults had true resistant hypertension (88%). Nineteen (19) of 22 with true resistant hypertension were at high risk for obstructive sleep apnoea (86%) when standardized questionnaires were used. The intervention study reported there was clinically meaningful blood pressure reduction (mean differences; systolic -6.43±11.94 mmHg, 95% CI -17.47 to 4.62/ diastolic -4.00±8.94 mmHg, 95% CI: -12.27 to 4.27) in the post-study group. However, the changes were not statistically significant. Qualitative study results suggested that the health literacy of the individuals living with resistant hypertension was low. Participants’ perceptions were mixed regarding the potential role of exercise as a therapeutic modality to manage their blood pressure.
Conclusions
The thesis confirmed that physical activity, in particular, aerobic exercise, is an effective therapeutic modality to manage blood pressure and improve sleep quality in a cohort with resistant hypertension and obstructive sleep apnoea risk. The prevalence of true resistant hypertension was high amongst participants with apparent resistant hypertension. Further, the risk of obstructive sleep apnoea may strongly be associated with the condition as higher percentage of participants had obstructive sleep apnoea risk. Exercise may be recommended as a non-pharmocological approach in management of adults with resistant hypertension and obstructive sleep apnoea risk. Health literacy needs to be improved for individuals living with resistant hypertension to empower them to take responsibility for the management of their condition. Fully powered studies need to be conducted to confirm the results from the quantitative studies piloted in this thesis. Careful consideration should be taken for recruitment to be inclusive of high risk population groups e.g. Māori, South Asians and with comorbidities e.g. chronic kidney diseases (CKD).