Insomnia in the News

by Anne Lambert, MS

The link between circadian rhythm disturbances, insomnia, and health issues is a prominent concern among sleep investigators. In the three widely divergent studies mentioned below we focus on emerging technology, possible links between insomnia and health, and a new treatment option for insomnia.

New Research on the Circadian System. Growing evidence indicates that exposure to irregular patterns of light and darkness can cause the human circadian system to fall out of synchrony with the 24-hour solar day, negatively affecting human health. A study by researchers in Rensselaer Polytechnic Institute's Lighting Research Center provides a new framework for studying the effects of circadian disruption on sleep disorders and other health problems.(1)

A small, head-mounted device was used to measure daily rest and activity patterns, as well as exposure to light that stimulates the circadian system. Forty-three day-shift and rotating-shift nurses wore the device for 7 days. Simultaneously, circadian disruption also was determined for a group of rats subjected to a consistent 12-hour light/12-hour dark pattern (n = 20) and a group subjected to a "jet-lagged" schedule (n = 20).

"We found that the circadian entrainment and disruption patterns for day-shift and rotating-shift nurses were remarkably different from each other, but remarkably similar to the patterns for the two parallel groups of nocturnal rodents," says Rea. "This ability to quantitatively define circadian light and dark for humans and for animals will allow a new class of meaningful studies of light as a stimulus for circadian entrainment or disruption to be undertaken […],says Rea.(1)

Circadian Function and Health. A study presented at Sleep 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies, LLC, highlights the growing concerns over links between sleep problems and serious illness. "Given the link between stress hormones and high blood pressure we decided to investigate the hypothesis that people who suffer low sleep efficiency are more likely to suffer from hypertension," said lead investigator Alexandros Vgontzas, MD, Co-Director, Sleep Research and Treatment Center, Department of Psychiatry, Pennsylvania State University, Milton S. Hershey Medical Center, Hershey, PA.

Vgontzas and colleagues randomly selected 1,741 volunteers who were classified as normal sleepers, as those who had difficulty sleeping, or as insomnia sufferers. Participants were also grouped according to their sleep efficiency. Fifty percent slept for more than 6 hours during the night, the next quartile slept 5 to 6 hours per night, and the bottom quartile slept less than 5 hours per night.

The results suggested that a combination of low total sleep duration and insomnia were very strongly linked to hypertension. People who slept fewer than 5 hours a night were five times more likely to suffer hypertension than people who slept well. "This suggests that the medical impact of insomnia has been greatly underestimated," commented Dr. Vgontzas. "I think that the association with depression and anxiety is fairly well established but we're behind in studying the physical effects of sleep problems." While conceding that measuring blood pressure in the subjects for only one night was a limitation of the study, he stated "There is a lot of work to be done [and] I find this data very exciting and promising."(2)

Treatment Option for Circadian Rhythm Disorders. Investigators are addressing many options for treating insomnia. Wang-Weigand and colleagues presented a study at the Sleep 2008 meeting that focused on ramelteon, an MT₁/MT₂ melatonin receptor agonist with a unique mechanism of action that selectively targets two receptors located in the brain's suprachiasmatic nucleus (SCN). The SCN is known as the body's "master clock" because it regulates 24-hour, or circadian rhythms, including the sleep-wake cycle. In the Wang-Weigand study, the majority of adults with chronic insomnia experienced ≥ 50% reduction in latency to persistent sleep throughout 6 months of ramelteon treatment. There were no significant next-day residual effects, and no rebound insomnia or withdrawal symptoms upon discontinuation of ramelteon.(3)

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References

1. Rea MS, Bierman A, Figueria MG, Bullough JD. A new approach to understanding the impact of circadian disruption on human health. J Circadian Rhythm 2008;6:7. Available at: http://www.jcircadianrhythms.com/content/6/1/7
2. Vgontzas A, Bixler E, Liao D, et al. Chronic insomnia with objective low sleep efficiency is associated with a high risk for hypertension. Presented at Sleep 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies, LLC. Baltimore, MD; June 7-12, 2008. Abstract 0685.
3. Wang-Weigand S, Ogrinc F, McCue M. A 6-month polysomnography study of ramelteon 8 mg in subjects wit chronic insomnia: post-hoc analysis of subjects with at least 50% reduction in latency to persistent sleep. Presented at Sleep 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies, LLC. Baltimore, MD; June 7-12, 2008. Abstract 0775.