The identification of blood biomarkers has helped researchers determine that aerobic exercise can reduce excessive daytime sleepiness, a common symptom of depression.
Investigators from the University of Texas Southwestern Medical Center in Dallas identified two biological markers for the condition, called hypersomnia. Hypersomnia is characterized by sleeping too much at night as well as excessive daytime sleepiness and is a symptom of major depressive disorder.
Researchers then discovered that aerobic exercise reduced the levels of the two biomarker proteins, resulting in reduced excessive sleepiness.
“Hypersomnia, as well as insomnia, have been linked in the development, treatment, and recurrence of depression,” said senior author Dr. Madhukar Trivedi. “Sleep disturbances are also some of the most persistent symptoms in depression. Identifying these biomarkers, combined with new understanding of the important role of exercise in reducing hypersomnia, have potential implications in the treatment of major depressive disorder.”
People with hypersomnia are compelled to nap repeatedly during the day, often at inappropriate times such as at work, during a meal, or in conversation. They often have difficulty waking from a long sleep, and may feel disoriented upon waking.
Other symptoms may include anxiety, increased irritation, decreased energy, restlessness, slow thinking, slow speech, loss of appetite, hallucinations, and memory difficulty. Some patients lose the ability to function in family, social, occupational, or other settings.
Researchers had previously found a negative loop in which sleep, inflammation, and depression interact and progressively worsen. The results of the current and previous research on insomnia suggest that exercise may be resetting this negative feedback loop, said Trivedi.
The researchers were able to identify the biomarkers based on blood samples provided by participants in the Treatment with Exercise Augmentation for Depression (TREAD) study, who were randomly assigned to two types of aerobic exercise to determine the effects of exercise on their depression.
More than 100 subjects ages 18 to 70 who had depression participated, and as part of the study had also agreed to provide blood samples.
In this study, researchers examined four biomarkers: brain-derived neurotrophic factor (BDNF) and inflammatory cytokines called tumor necrosis factor alpha, and two interleukins, IL-1β and IL-6, from blood samples collected before and after the 12-week exercise intervention.
Researchers found that reductions in two biomarkers, BDNF and IL-1β, are related to reductions in hypersomnia.
“Identification of biomarkers that uniquely predict or correlate with improvements in hypersomnia and insomnia is an important step toward more effective treatment of MDD [major depressive disorder],” said lead author Dr. Chad Rethorst, assistant professor of psychiatry with University of Texas Southwestern’s Center for Depression Research and Clinical Care.
Interestingly, the two biomarkers appear specific for hypersomnia and not for changes in insomnia.
Rethorst explains that while previous analysis of the TREAD data demonstrated significant reductions in insomnia symptoms with exercise, the two biomarkers identified above did not correlate to changes in insomnia.
Researchers did find, however, that lower baseline levels of IL-1β were predictive of greater improvements in insomnia. The findings suggest distinct mechanisms are involved in insomnia versus hypersomnia, and that further research will be needed to identify the appropriate biomarkers for insomnia.