Saudi Cultural Missions Theses & Dissertations
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Item Restricted Do Respiratory Influences on Cardiovascular Regulation Provide Early Markers of Hypertension in Young Adults with Family History of Hypertension?(2023-05-05) Al Enazi, Fahad; Marshall, Janice; Coney, AndrewBackground: Hypertension is well-known leading cause of the majority of cardiovascular diseases. Individuals with a parental history of hypertension (FH+) have a two-fold greater risk of developing hypertension than those without parental hypertension (FH-). Objective: This PhD project had three main aims. First, to elucidate whether young normotensive adult FH+ already have disturbed autonomic regulation of arterial blood pressure (ABP) relative to FH- at rest and in response to everyday stressors such as postural manoeuvres and environmental stressors. Second, to investigate whether slow breathing normalises autonomic dysregulation in FH+. Third, to assess whether slow breathing acutely or following training reduces ABP and restores autonomic regulation in normotensives and hypertensives. Methods: The first and second aims were explored by recording arterial blood pressure (ABP), a range of haemodynamic variables, heart rate variability (HRV) and baroreceptor reflex sensitivity (BRS), in young normotensive FH+ and FH- men and women at rest, during and following acute mental stress (Stroop colour-word test) and during acute slow breathing at 6 breaths/minute. The third aim was evaluated by a systematic review and meta-analysis on the effects of device- and non-device guided slow breathing acutely and by training for ≥4 weeks on ABP and autonomic regulation of ABP in normotensives and hypertensives. Results and Conclusion: The experimental studies showed no differences between FH+ and FH- at rest. However, FH+ showed exaggerated increases in ABP and total peripheral resistance to mental stress relative to FH-. On the other hand, HRV, which mainly reflects vagal influences on the heart, was reduced during mental stress in FH+ and FH- and consistent with inhibition of the baroreceptor reflex being a characteristic of the defence response, vagal BRS was also reduced in FH+ and FH-. However, sympathetic BRS to a fall in ABP assessed by the squat to stand test was depressed by mental stress in FH- but not FH+. These findings provide novel evidence that sympathetic control of ABP is disturbed in young adult FH+ such that repeated exposure to mental stressors would be expected to increase their risk of hypertension. Acute slow breathing reduced ABP in both FH+ and FH- but reduced TPR in FH- only. Concomitantly, HRV was increased in both groups, while vagal BRS was increased in FH+ only. Theses novel results suggest that FH+ are more resistant to the ability of slow breathing to reduce sympathetic tone, but that vagal influence are normalised. Importantly, the systematic review and meta-analysis, demonstrated that slow breathing is effective in both hypertensives and normotensives in lowering ABP, enhancing HRV, and improving BRS, at least in normotensives. Thus, collectively the results indicate that slow breathing training should help to reduce abnormal autonomic regulation in young FH+ by increasing vagal regulation of the heart and decreasing sympathetic activity to the heart and vasculature, so lowering their future risk of hypertension.26 0Item Restricted The Relationship Between Childhood Trauma and Adult Aggressive Behaviour(2022) Alomayrini, Hamad; Yaneva, Mira; Dymond, HarrietRelationships connecting different kinds of childhood trauma with the aggressive behaviour in adulthood have been previously investigated. The majority of the studies have shown that childhood trauma could potentially lead to an adult aggressive behaviour in adulthood. This current study aims to investigate this hypothesis as well as to determine the potential factors in childhood trauma that could increase the adult aggressive behaviour. In that intention, an online survey was prepared using the "Adverse Childhood Experiences (ACEs) Questionnaire" and "Buss Perry Aggression Questionnaire (BPAQ)" to assess the childhood trauma experiences and the aggressive behaviour aspects of 100 participants. In the data analysis, the ACEs and BPAQ scores were calculated for each individual, and then a statistical analysis was performed. The results have shown that the childhood trauma exposure was directly linked to an adult aggressive behaviour. In addition, the regression models showed significant positive correlations between the childhood trauma and all the types of the aggressive behaviour. In conclusion, and in view of the obtained results, in addition to previous literature, it is extremely important to increase awareness about this subject for all parents, guardians and caregivers, in order to prevent childhood trauma in the first place and therefore adult aggression.36 0Item Restricted Is early evidence of cardiovascular and respiratory disease already present in young healthy South Asians and White Europeans: can this be modified by respiratory training?(2023) Alqahtani, Mobarak Khalid; Marshall, Janice; Coney, AndrewBackground: Hypertension is well-known as the forerunner of most cardiovascular diseases. The prevalence of hypertension, coronary artery diseases, and other cardiovascular diseases has been reported to be higher among men and women of South Asian ethnicity than White Europeans. Further, South Asians have lower lung function than White Europeans, and poor lung function has been reported as a risk for developing future hypertension and cardiovascular disease. Objective: The overall objective of this PhD project was to investigate whether young healthy normotensive South Asian adults show early markers of autonomic dysfunction at rest and in response to mental stress that may lead to future hypertension and to assess whether acute or long-term slow breathing may have beneficial effects on autonomic regulation of arterial blood pressure (ABP), especially in South Asians. Methods: Three studies were conducted to test the hypothesises. The first compared haemodynamic variables, heart rate variability (HRV) which largely reflects vagal influences on HR and baroreceptor reflex sensitivity (BRS) between young normotensive South Asian and White European adults at rest, in response to acute slow breathing at 6 breaths/minute and acute mental stress. The second tested whether there were sex-dependent differences in these responses within and between ethnicities. Thirdly, a systematic review was performed to evaluate the effects of acute slow breathing and slow breathing training on autonomic regulation of ABP in healthy, normotensive South Asians Results and Conclusions: Young South Asians showed a pronounced pressor response to mental stress associated with greater peripheral vasoconstriction than occurred in White Europeans, vasoconstriction being most prevalent in South Asian women. These novel findings are consistent with mental stress facilitating the development of hypertension in South Asians. Further, White Europeans showed the characteristic inhibition of the vagal and sympathetic component of BRS in mental stress, but both components of BRS to falls in ABP were preserved in South Asians, possibly protecting them against vasovagal syncope but facilitating their risk of hypertension. By contrast, acute slow breathing decreased ABP and increased HRV in both young South Asians and White Europeans but decreased tonic peripheral vasoconstriction in WEs only. These new findings suggest that South Asians may be more resistant to the beneficial effects of slow breathing on sympathetic activity. However, the systematic review and meta-analysis showed that both acute slow breathing and four weeks of slow breathing training were able to decrease ABP and increase HRV in healthy normotensive South Asians. Thus, these outcomes are consistent with our hypotheses. Importantly, considered together with our experimental findings they suggest that a study should be performed to evaluate whether slow breathing can provide a beneficial therapeutic intervention for young normotensive South Asians and reduce their risk of future hypertension and cardiovascular disease.33 0