Just one night of poor sleep is known to impair cognitive function, whilst habitual sleep loss may accelerate cognitive decline with ageing and increase dementia risk. Despite this, approximately 75% of the Great British public fail to achieve 7 hours of sleep per night. Furthermore, only 20% of Australians sleep through the night uninterrupted, which is thought to cost $45.2 billion per year (including direct healthcare costs and productivity losses).
The ways in which sleep influences these important outcomes is not well understood, and interdisciplinary research is needed to address this contemporary and pertinent public health concern. Emerging evidence indicates that both sleep quantity and quality may be important, in addition to an individual’s preferred sleep-wake timing (“chronotype”). All three of these dimensions of sleep health have been linked to cognitive and health outcomes, and all three change over the lifespan. Specifically, habitual sleep duration is greatest in young people and declines with age, whilst older adults may experience poorer sleep quality and changes in sleep timing. Adolescents represent the age group with the most extreme propensity towards going to, and rising from, bed later (i.e. a “night owl” rather than “morning lark”). This change is thought to be an intrinsic part of pubertal maturation, and may explain why cognitive function tends to be higher in the afternoon compared to the mornings in this group. Following adolescence, there is a gradual shift towards sleeping and rising earlier, which becomes particularly pronounced in older adults.
This PhD studentship intends to scrutinize the influence of sleep loss across the lifespan in order to further our understanding of the importance of sleep quantity, quality and chronotype on outcomes related to learning and cognitive decline. These include both functional, and physiological measures, which will be assessed in a series of interventional studies. The research will pool expertise across a diverse field, including vascular physiology, sleep science and biomedical engineering, in order to provide insight from a powerful, multi- and inter-disciplinary perspective. In so doing, the collaboration will enhance the research capacities of both laboratories (Exeter and Queensland). This knew knowledge and shared expertise will then provide an excellent platform from which to attract future funding from grant bodies concerned with not only ageing and dementia, but also learning and education policy.
Detailed Project Description:
Sleep is an essential recuperative and restorative process. Just one night of sleep loss has been shown to impair a variety of cognitive abilities. These abilities are essential for learning, work, social participation, and independence throughout life. Habitual sleep loss is also a risk factor for cognitive decline and dementia. Accordingly, understanding how sleep influences these processes is an important research priority.
The brain stores very little energy, which means that increases in cerebral metabolism during a cognitive task must be supported by region-specific brain blood flow. The ability to match increases in brain activation with blood flow (“neurovascular coupling”) is critical for cognitive health. This ability generally declines with age, and is thought to precede cognitive decline and dementia. Alterations in this fundamental process are also observed following sleep loss, and may contribute to the alterations in cognitive ability associated with poor sleep. However, few studies have experimentally addressed this.
There is also a tight coupling between cerebral metabolism and blood flow during sleep, and this is dynamic across sleep stages. For example, brain blood flow increases during rapid eye movement (REM) sleep. Reduced blood flow during REM sleep has been associated with poorer cognitive function and implicated in cognitive decline. Rhythmic neural activity and arterial pulsations in the brain during non-REM sleep are also thought to aid the clearance of ’waste’ compounds from the brain, but the effectiveness of this “pump” may be lost without close neurovascular coupling. Emerging data indicate that these processes are also altered due to sleep loss, and may provide a further mechanism that links poor sleep to poor daytime cognitive outcomes.
The aim of this PhD studentship is to address these research gaps in order to better understand the relationship between sleep, cognitive function and cerebrovascular function. To do so, will require symbiotic collaboration between research groups at Exeter and Queensland.
Adolescents, adults, and older adults will be recruited into a series of experimental trials, utilising existing links (e.g. local schools) and infrastructure (the Exeter 10,000). Sleep will be manipulated via established paradigms including partial or complete sleep restriction, and via manipulation of circadian timing of sleep and wake times. This will only be possible via expertise from Drs Smith and Mann (Queensland). We will observe the influence of these manipulations in sleep on a variety of age-appropriate cognitive outcomes in each age group. These may include measures of reaction time, cognitive throughput, decision making and risk, attention and concentration, and potentially other indices such as wake EEG, heart-rate variability, and pupillometry. We will also quantify any changes in the coupling between cerebral metabolism and brain blood flow across a variety of cognitive challenges by using the minimally obtrusive transcranial Doppler techniques which Dr Bond has extensively used in adolescents and adults (Exeter).
Finally, the adolescents recruited in Year 1 of the PhD will be invited back in Year 3, in order to understand whether the effects of sleep loss change across pubertal maturation, which is a contemporary concern amongst education policy makers.
The research project will involve working with under 18 year old's and therefore the applicant may need appropriate clearance through the Disclosure and Barring Service (DBS) check if working with adolescence with the UK and a National Police Check whilst working in Australia. Furth details and guidance would be provided to the successful candidate.
Find out more about the PhD studentships https://www.exeter.ac.uk/global/quex/phdstudentships/opportunities/ and https://scholarships.uq.edu.au/scholarship/quex-phd-scholarship
The closing date for applications is midnight on Tuesday 30th August 2022 (BST), with interviews taking place week commencing 19th September 2022. The start date is expected to be Monday 9th January 2023.
For more information and to submit an application please visit - https://www.exeter.ac.uk/study/funding/award/?id=4496