"It moves [insomnia] patients into a deeper sleep," lead author Eric Nofzinger, MD, a professor of psychiatry at the University of Pittsburgh, in Pennsylvania, told Medscape Neurology.
The findings were presented here at SLEEP 2009: 23rd Annual Meeting of the Associated Professional Sleep Societies.
Increased Metabolism
The work grew out of earlier brain-imaging studies of healthy individuals as they fell asleep. Those studies showed a reduction in metabolism in the frontal cortex in those without insomnia, but insomniacs experienced an increased metabolism compared with healthy volunteers, both before going to sleep and during non–rapid eye movement (NREM) sleep. Other evidence suggests that people with insomnia have a generally higher metabolism, including faster heartbeats and hyperarousal.
The approach is designed to counter the metabolic changes seen in brain images, Dr. Nofzinger told Medscape Neurology. "We're trying to push that back to the normal condition by applying surface cooling."
Neurosurgeons have used cooling to reduce brain metabolism, so the team designed a cap that could be used to apply cooling to the frontal cortex.
The researchers screened 148 subjects and identified 12 that met Diagnostic and Statistical Manual of Mental Disorders, 4th ed (DSM-IV) criteria for primary insomnia. Eight of these completed the study.
Patients used a medical device that overlay the frontal cortex on the scalp and delivered neutral temperature (control) or a mild hypothermic effect for 60 minutes. Subjects served as their own controls. The treatment was applied before bedtime and during the first cycle of NREM sleep. The researchers analyzed core body temperature and NREM sleep using 18F-fluorodeoxyglucose positron-emission-tomography ([18F]-FDG PET) scanning.
Hypothermic treatment led to reduced metabolism in the underlying frontal and cingulate cortex (T = 8.2; corrected P < .005). Five of 8 patients experienced reduction in whole brain metabolism with the treatment.
Treatment also led to an accelerated reduction in core body temperature at sleep onset (group F = 3.68; 1-tailed P = .03; time F = 53.6; P <.0001; group x time F = 1.7; 1-tailed P = .10). Of the patients, 75% reported sleep-related improvements, including a decrease in distracting thoughts, improved sleep maintenance, and more refreshing sleep.
The next step will be dosing studies and investigating the results of applying treatment at different periods during the night, he said.
Future research will include dose-ramping studies and treatment at different periods during the night. Dr. Nofzinger is also developing a version of the cooling device that is portable and that people can use at night. He has also started a company called Cerêve to commercialize the research.
Nonpharmacologic Solutions Preferred
The study is significant because there are few effective treatments for insomnia, and most patients say they prefer nonpharmaceutical interventions, according to Colin Espie, PhD, director of the University of Glasgow Sleep Centre, in Scotland, who attended the poster session where the work was presented and was not involved in the research. "This would be a possibility," he told Medscape Neurology.
"The theoretical basis is interesting," Dr. Espie added, but he also emphasized that the study was preliminary. "It's well-controlled, [but] it's a proof-of-concept study. We'll have to see what the clinical impact is in terms of performance during the day."
Others think it should give physicians a new way to think about insomnia and its causes. "It's a very provocative [study]," Dennis Nicholson, MD, medical director of Pomona Valley Hospital's Sleep Disorders Center, in California, told Medscape Neurology.
"It should trigger the thinking that [insomnia] is not just psychological," Dr. Nicholson said. In most cases, insomnia is treated as a psychological problem, with cognitive behavioral therapy or drugs in some nonspecific way. "This is the first thing I've seen that we could specifically target brain metabolism to improve sleep," he said.
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