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What are Circadian Rhythms?

Circadian rhythms are essential for synchronising the daily cycle of all organisms, keeping internal body functions aligned with the dawn-dusk cycle. In humans, it governs a host of critical physiological and behavioural processes including body temperature, cardiovascular function, hormone production, and sleep.

Disruption to our sleep and circadian rhythms are widely experienced in our communities, with the scope of the problem often underreported and underdiagnosed. Common sufferers range from teenagers, new mothers and shift workers, to individuals with psychiatric conditions and the severely Vision Impaired. Importantly, sleep and circadian rhythm disruption is an underlying, and often undetected, feature in many of the most challenging diseases of our time, including cardiovascular disease, metabolic disorders, cancer and neuropsychiatric diseases.

What happens if they are disrupted?

Disruption of daily sleep and circadian rhythms is also commonly experienced by individuals with severe visual impairment. This disruption is often due to a reduction or total loss of light being detected through the eyes to the brain. In humans, our internal circadian rhythms run in cycles slightly longer than 24-hours. These rhythms require daily resetting by external time cues to synchronise our sleep and wake timing to the Earth’s 24-h day and night cycle. External time cues include feeding, activity and exercise, but most importantly, light is the master time cue for resetting our daily rhythms.

In severely visually impaired individuals, the mechanistic reduction or failure to receive light impacts the ability to adequately synchronise to the Earth’s 24-hour day. In some, this can result in an incremental delay in circadian timing by as much as 60 minutes per day and periodically cycle through restful night-sleep bouts to symptoms of insomnia with episodes of poor night sleep and excessive daytime sleepiness and napping.

In order to treat circadian rhythm disruption, knowledge of an individual’s internal (circadian) time is critical to first make a definitive diagnosis of the underlying disruption, and secondly, to time the delivery of treatments appropriately. Critically, however, a major challenge of our field lies in the lack of robust diagnostic tools available that are capable of accurately determining internal circadian time, thus hindering the development of effective, targeted therapeutics for sleep and circadian rhythm disorders. 

Current methods used to assess circadian time in clinical and research settings suffer shortcomings that limit their utility. The current gold-standard method to assess circadian time requires serial sampling of the circadian-driven hormone melatonin from blood, saliva, or urine over 8 to 24 hours. Such methods are time-consuming, costly and burdensome to the patient and healthcare practitioners, and not feasible or sustainable for effective long-term monitoring in public health settings. Fulfilling this unmet need necessitates the development of a novel method that can accurately predict circadian time with minimal sampling and is invulnerable to variability across individuals and under a range of conditions.

Disruption to normal circadian rhythms can have both short and long-term negative psychological and physiological impacts.

Acute short-term impacts include impulsivity and loss of empathy, memory impairment, loss of attention, mood instability, reduced cognition and creativity, and a reduction in information processing abilities. Chronic long-term disorders include depression, anxiety, sleep-wake disorders, cardiovascular disease, immune suppression, cancer, metabolic syndrome and Type 2 Diabetes.

What will we do?

Many assumptions are made around sleep disorders, particularly those disorders that are associated with circadian rhythm disruption. Many people assume that if you cannot see, you naturally experience sleep difficulties, however, we are finding that the type and cause of blindness can have a large impact on the type of disruption experienced.

We believe that with the right treatment and therapies, individuals with a visual impairment can resynchronise circadian rhythms and improved patterns of sleep which in turn will improve their health and wellbeing.

The aims of the research study are two-fold: first, to examine the impact that sight loss has on sleep and circadian rhythms in the Blind Veterans UK community, and; second, to assess new methods to more simply diagnose underlying circadian rhythm disruption for effective, targeted treatment.

To meet these aims, a series of studies have been developed in close collaboration between the University of Oxford, Circadian Therapeutics and the Blind Veterans UK Research and Innovation team. The research is planned in two main parts:

We are mapping, in detail, the sleep patterns and circadian cycles of blind veterans, with the aim of developing a simple and non-invasive diagnostic tool to diagnose underlying circadian rhythm disruption. This new method will allow us to more appropriately treat sleep and circadian rhythm disturbances. We hope that this will lead to the development of an effective therapeutic solution in pill form.

Blind veterans will take part in a research trial which includes 3 phases:

  • Part 1: Sleep Health Survey

  • Part 2: Sleep and Circadian Health Study:

    • Part 2A: Sleep and circadian assessment

    • Part 2B: Circadian quantification

“I volunteered to take part in the study because I believe research into vision impairment is very important and relevant. I wanted to be able to help in some way, to be useful to those in the future that may face the same issues that I face and in a sense it gave me a way to continue to serve. I enjoyed being able to come down to the Blind Veterans UK office and meet the staff who I don’t usually get to speak to face to face. Being able to meet and work with the Research Team was great- they are a great group of people. I was hugely impressed with the scientists that I worked with, they are fantastic people who explained everything to me clearly, made sure that I knew what was going on at all times and were just very easy to get along with. I can’t understand why more people don’t get involved with research!”
A blind veteran taking part in the study

Our partners in this research

Circadian Therapeutics, a spin-off from Oxford University, delivers world-leading science research into understanding the molecular control of circadian rhythms. This enables them to develop unique therapeutic methods to treat serious diseases associated with disruption of the human body clock.

University of Oxford, is a world-leading centre of learning, teaching and research and the oldest university in the English-speaking world.

About Professor Russell Foster

Russell Foster is Professor of Circadian Neuroscience and the Head of Department of Ophthalmology. He is also a Nicholas Kurti Senior Fellow at Brasenose College. Prior to this, Russell was at Imperial College where Russell was Chair of Molecular Neuroscience within the Faculty of Medicine. Russell Foster’s research spans basic and applied circadian and photoreceptor biology.

He received his education at the University of Bristol under the supervision of Professor Sir Brian Follett. from 1988–1995 he was a member of the National Science Foundation Center for Biological Rhythms at the University of Virginia and worked closely with Michael Menaker. In 1995 he returned to the UK and established his group at Imperial College. For his discovery of non-rod, non-cone ocular photoreceptors he has been awarded the Honma prize (Japan), Cogan award (USA), and Zoological Society Scientific & Edride-Green Medals (UK). He is the co-author of “Rhythms of Life” a popular science book on circadian rhythms.

Professor Russell Foster
Professor Russell Foster
“The impact of eye loss or severe eye damage plunges individuals into a world that can best be appreciated as having unremitting jet lag. I fully expect that the research we undertake with Blind Veterans UK will restore sleep/wake timing to these individuals and give them back their sense of biological time.”
Professor Russell Foster CBE, FRSB, FMedSci, FRS


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