Lay summary by Arman Mohseni
Edited by Crystal Han
This lay summary is written based on the paper by Francesca Baschieri, Pietro Guaraldi, Federica Provini, Monica Chiogna, Giorgio Barletta, Annagrazia Cecere, Giuseppe De Scisciolo, Pietro Cortelli, and Giovanna Calanadra-Buonaura. Read the original article here.
What was the purpose of the study?
Core body temperature (referred to in this study as “Tcore”) is regulated based on feedback from temperature-sensing organs that are located throughout the body. Much like a thermostat in a building, the body increases its core temperature when it senses that the surrounding environment is cold and decreases its core temperature when it senses that the environment is warm, in order to maintain its ideal temperature, or “setpoint.” In people with spinal cord injury, this feedback may be interrupted, leading to inefficient regulation of Tcore.
The setpoint of Tcore normally fluctuates in a cyclical fashion throughout the day. For example, during some phases of sleep, Tcore is set lower than during wakefulness, to conserve energy. During REM (Rapid Eye Movement) sleep, the regulation of Tcore stops entirely, and Tcore matches the temperature of the environment more closely. For people with SCI, the inefficient regulation of Tcore may affect sleep quality, as suggested by the higher rate of sleep disorders reported in this group.
The purpose of this study is to address three questions:
- how SCI affects the regulation of Tcore in both sleep and wakefulness
- whether individuals with SCI in the lower region of the spine (i.e., lumbar regions) and individuals with SCI in the higher region of the spine (i.e., cervical regions) differ with respect to Tcore regulation
- how SCI impacts the different stages of sleep.
How was the study done?
This was a study with 19 male adult participants. The groups were designated depending on the level of the spinal cord injury:
- 5 of the participants had a cervical spinal cord injury and had tetraplegia. This was the cSCI group.
- 7 of the participants had a thoracic spinal cord injury and had paraplegia. This was named the tSCI group.
- 7 of the participants were people without SCI, who were included as a control group for comparison.
The study took place over a 24-hour period. The participants were fitted with a rectal thermometer to measure Tcore, as well as having their heart rate and breathing monitored. Participants were instructed to sleep as much as they would like in a temperature and humidity-controlled laboratory environment for a 24-hour period. All participants were given the same diet for the duration of the experiment, and abstained from alcohol and caffeine during the experiment.
What did the study find?
During the day, the Tcore for the tSCI group and the control group were similar in every aspect. The cSCI group had a lower Tcore before noon, but had elevated body temperatures during the day.
During nighttime, the Tcore in the tSCI group and the control group were similar in every aspect, demonstrating a nighttime decrease in Tcore. However, the cSCI group did not exhibit this decline in Tcore at nighttime.
Both the tSCI and cSCI groups spent significantly less time in the deepest stage of sleep, N3, compared to the control group.
Why is this study important?
This study showed that spinal cord injury, regardless of location, caused a decrease in the duration of the deepest sleep stage, thereby decreasing sleep quality. The study also showed that individuals with cSCI have abnormal regulation of their core body temperature.
Finally, this study suggests an overall relationship between Tcore regulation and sleep in individuals with an SCI, encouraging further research on how interventions to improve sleep may improve Tcore regulation, or vice versa.
cSCI: Cervical spinal cord injury
tSCI: Thoracic spinal cord injury
Tetraplegic: Loss of function in all four limbs
Paraplegic: Loss of function in legs
REM: A stage of sleep characterized by rapid eye movement and dreaming
N3: A stage of particularly deep sleep, which is characterized by regeneration and the commitment of memories to long-term storage