The Influence of Oral Contraceptives on the Autonomic Nervous System

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dc.contributor.advisorEdgell, Heather
dc.contributor.authorPereira, Tania De Jesus
dc.date.accessioned2024-11-07T11:04:30Z
dc.date.available2024-11-07T11:04:30Z
dc.date.copyright2024-06-24
dc.date.issued2024-11-07
dc.date.updated2024-11-07T11:04:29Z
dc.degree.disciplineKinesiology & Health Science
dc.degree.levelDoctoral
dc.degree.namePhD - Doctor of Philosophy
dc.description.abstractThis thesis aims to determine the effects of oral contraceptives (OC) on resting autonomic function, autonomic reflex activation, and cerebral blood flow (CBF). The first study systematically reviewed the effects of OC on any aspect of autonomic function. A search strategy was applied to several databases, and 6,148 citations were retrieved. Forty studies were included and grouped by measurement of autonomic function investigated. Physiological responses to isolated reflex activation (i.e., the chemoreflex, mechanoreflex and metaboreflex) were influenced by OC; however, the effect of OC on resting autonomic indices and response to autonomic stressors was less consistent. These inconsistencies may be caused by hormone dosage within OC formulations or stressor intensity. The second study investigated the influence of OC on the cardiorespiratory response to metabo- and mechanoreflex activation in the arm and leg. Two minutes of isometric handgrip or plantarflexion exercise-induced similar increases in blood pressure (BP) and ventilation (VE) in both OC and non-OC users (NOC). While both exercise modalities increased VE, neither OC nor NOC exhibited a sustained increase in VE during 3 minutes of arm or leg post-exercise circulatory occlusion. All women increased BP and VE during 3 minutes of arm or leg passive movement. Considering that all women had a cardiorespiratory response to mechanoreflex but not metaboreflex activation, we suggest that the mechanoreflex may drive VE during exercise in women. The final study investigated the influence of OC and the menstrual cycle on CBF and cerebral autoregulation (CA) during 5 minutes of hypercapnia (5%). Regardless of menstrual or pill phase, all women improved high frequency and very low frequency dynamic CA (dCA) during hypercapnia, although low frequency dCA decreased in the high hormone phase of NOC and the low hormone phase of the pill cycle. During hypercapnia, the presence of endogenous hormones attenuated dCA, while the chronic use of exogenous hormones (i.e., OC) chronically attenuated dCA (i.e., when hormones were not present). The findings of this thesis shed light on the complex influence of OC on autonomic function, CBF and different physiological stressors, emphasizing the need for further research to fully elucidate its impact. There is a further need to control for menstrual cycle, OC formulation, dose, progestin generation and/or type when studying factors affecting autonomic physiology.
dc.identifier.urihttps://hdl.handle.net/10315/42418
dc.languageen
dc.rightsAuthor owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.
dc.subjectKinesiology
dc.subjectPhysiology
dc.subject.keywordsPharmaceutical
dc.subject.keywordsHormones
dc.subject.keywordsHemodynamics
dc.subject.keywordsBrain blood flow
dc.subject.keywordsVentilation
dc.subject.keywordsTranscranial Doppler
dc.subject.keywordsAutoregulation
dc.subject.keywordsExercise
dc.subject.keywordsBirth control
dc.subject.keywordsHypercapnia
dc.subject.keywordsChemoreflex
dc.subject.keywordsMetaboreflex
dc.subject.keywordsMechanoreflex
dc.titleThe Influence of Oral Contraceptives on the Autonomic Nervous System
dc.typeElectronic Thesis or Dissertation

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