Scientists have found evidence that SCI disrupts the body’s internal clock. Dr. Andrew Gaudet, a University of Texas at Austin researcher and former ICORD investigator, is working hard to confirm and better understand the mechanisms of this disruption — and develop strategies to lessen the impact.
The human body runs on a 24-hour biological clock known as the circadian system. It’s a vital system, playing an important role in regulating virtually all of our body’s functions. The actions of the circadian system are triggered by light—specifically, blue light. The presence of light at the beginning of the day triggers the circadian system to tell the body it’s time to get up. As our world becomes darker each night, it tells the body it’s time to sleep and focus on the processes of replenishing our cells. These are known as circadian rhythms.
Scientists have hypothesized for decades that any injury to the spinal cord compromises our circadian system and circadian rhythms. Many people with SCI report significant sleep disorders. But the extent and implications of this circadian disruption, from acute to chronic SCI, aren’t well understood to this day.
Enter Dr. Andrew Gaudet, an assistant professor of psychology at the University of Texas, who focuses his research on the link between SCI and circadian functioning.
Gaudet’s interest was first tweaked as an undergrad at UBC, he worked in the lab of ICORD’s Dr. Matt Ramer, studying the immune response after SCI. After graduating with his PhD in 2010, he moved to Ohio State University to work with Dr. Phil Popovich, who is renowned for his work in nervous and immune system interactions after SCI.
“I completed postdoctoral research between 2011 and 2014, studying inflammation and axon growth after SCI,” says Gaudet. “In that time, I also met my future wife—a fellow researcher named Dr. Laura Fonken— and we collaborated on research related to inflammation of the nervous system, metabolism, and biological clocks. These studies continued at our next research positions, at University of Colorado Boulder. This is where Laura and I collaborated, along with my supervisor Dr. Linda Watkins, in completing studies related to SCI and biological clocks.” The couple then secured their current positions as assistant professors at The University of Texas at Austin, where their research collaboration is almost exclusively circadian functioning after SCI.
Circadian disruption: much more than a bad night’s sleep
Probably the most well-known form of circadian disruption is jet lag. When we cross time zones rapidly, our bodies are unable to adjust rapidly to the new light cycle and we “feel bad” for several days. But long-term circadian disruption has been demonstrated to seriously impact our health and has been linked to obesity, cardiovascular issues and mental health conditions such as anxiety and seasonal affective disorder.
Most able-bodied people can make a conscious decision to make life changes that reduce circadian disruption. But SCI by itself seems to cause long-term circadian disruption, and those with SCI don’t have the luxury of switching it off. This underscores the importance of trying to better understand the mechanisms behind SCI-related circadian disruption and develop strategies to reduce or prevent it.
Biological rhythms and post-SCI influences
“I’m developing a research program that involves SCI, and determining how biological rhythms influence post-SCI metabolism and functional recovery,” says Gaudet. “My wife is an expert at neuro-immune interactions, endocrinology, metabolism, and circadian rhythms.”
This husband and wife synergy was evident with the recent publication of an animal study that confirms the disruption of circadian functioning in the first days and weeks after SCI delays— and suggests the disruption might actually limit recovery.
“Previous research focused on how SCI affects other parts of the body, but this is the first study to reveal the widespread disruption an injury might have on these rhythms,” says Gaudet. “It was known that SCI impairs metabolism. It was also known that circadian disruption alters metabolism. However, no one had systematically addressed this question: does SCI disrupt circadian rhythms?”
In order to explain his research, Gaudet suggests we think of the circadian system as a corporate structure.
It consists of a president or CEO— the suprachiasmatic nucleus of the brain. That part of the brain only responds to light—particularly blue light—from the eyes, and sends this information to middle managers, which include certain hormones, body temperature, movement and activity, eating, and autonomic function. The middle managers integrate this information from the CEO with other information from the body—about stress, for example— in order to tell every organ and cell in the body what time it is, and what each cell should be doing. So the liver knows what time it is and is ready for food at 7 am, whereas the liver releases stored energy and is not timed for food at 12 am.”
Gaudet and Fonken compared the rhythms of two of these middle managers, body temperature and movement/activity, in two groups of rats—one with moderate SCIs, the other uninjured. What they observed was that these rhythms almost completely disappeared immediately after injury, but gradually recovered within one to two weeks. They also assessed levels of another middle manager, the hormone corticosterone, and found that it too was disrupted soon after injury, but recovered within two weeks.
“Overall, this moderate injury disrupted rhythms in various middle managers and outputs of the circadian system.”
Armed with this knowledge, he wants to push forward with research to determine if and how circadian disruption also restricts neurological recovery.
“Since every cell in our body contains its own clock, and this clock is linked to many other functions, I would predict circadian disruption could worsen inflammation, increase post-injury damage, and harm potential repair mechanisms,” he says.
But it might not all be bad news—accelerating recovery of circadian rhythms soon after injury could boost the body’s ability to limit further damage and to repair itself.
“If disruption of these rhythms harms recovery after SCI, efforts to restore a patient’s routines—for example, optimizing daily schedules of meals, sleep, physical rehabilitation and bright light—could promote recovery,” Gaudet explains.
Early after injury, there are several strategies that could be used to boost rhythms.
Optimizing the amount and timing of light would be a great start: bright light in the morning and dark nights. If light at night is necessary, then it could be red light, which does not activate the circadian system. When possible in the intensive care unit, hospital staff could try to consolidate visits—studies suggest that an ICU patient receives 50 or more visits per night; this surely disrupts sleep at this critical time post-injury.”
Other strategies could include ensuring patients eat at the optimal time of day (particularly breakfast), avoid eating anything beyond early evening, exercise only during the day (ideally morning), and avoid stress. Gaudet says there are also drugs being tested that can alter the circadian system.
“Of course,” he says, “none of this is a miracle cure, but these are easy steps in the right direction, it could help with recovery, and it also would provide a healthier state for treatment with other therapies.”
Dr. Gaudet Recommends:
- Getting as much bright light as possible in the morning (e.g., sitting near a window or going outside)
- Using low light and/or red light in the evening (especially an hour before bed)
- Using blue-light filters on your phone and other devices in the evening and before sleeping
- Eating a meal in the morning
- Avoiding eating anything beyond early evening or during the night
- Scheduling activity or rehabilitation for the morning to boost rhythms
- Avoiding stressful activities in the evening
- Keeping a regular sleep schedule
Gaudet says anyone with chronic SCI should consider their circadian system and its relation to health when making day-to-day decisions.
“Individuals with SCI are more susceptible to worsened body composition, obesity, cardiovascular disease, and metabolic issues,” he says. One potential take-away is that circadian health may be particularly important for people with SCI. Individuals with chronic SCI may be more sensitive to circadian disruption, which could influence overall health and metabolism.
Light, eating, activity, stress, and sleep all feed in to the circadian system, so optimizing timing of these factors when possible could be useful for individuals with chronic SCI.”
Visit www.gaudetlab.com to read more about Dr. Gaudet and his work.
This article first appeared in our Spring 2019 issue of The Spin and has been edited for our blog. Read the full version alongside other stories including:
- Hit the Wall – Wallgym
- Grow Your Own – Therapeutic cannabis
- Pleasure Principles
- and more!
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