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Pitt Study Finds Loud Snoring and Insomnia Symptoms Predict Development of Metabolic Syndrome

PITTSBURGH, Dec. 1, 2010 – A University of Pittsburgh School of Medicine study finds loud snoring and two common insomnia symptoms―difficulty falling asleep and unrefreshing sleep―each significantly predicted the development of metabolic syndrome. The study emphasizes the importance of screening for common sleep complaints in routine clinical practice. The findings are reported in the December issue of SLEEP, the official publication of the Associated Professional Sleep Societies.

The Pitt study provides the first prospective evidence to support a link between common sleep complaints and metabolic syndrome.

“This study shows us that a broader array of commonly reported sleep symptoms, including insomnia and sleep-disordered breathing symptoms, predict the development of metabolic syndrome, a key risk factor for cardiovascular disease,” said Wendy M. Troxel, Ph.D., lead author and assistant professor of psychiatry and psychology at Pitt’s School of Medicine. “It was rather striking that the effects of difficulty falling asleep and loud snoring were largely independent of one another.”

According to the National Heart, Lung, and Blood Institute, metabolic syndrome is a group of obesity-related risk factors that increases an individual’s risk of heart disease, diabetes and stroke. A person with at least three of these five risk factors is considered to have metabolic syndrome: excess abdominal fat, high triglycerides, low HDL cholesterol, high blood pressure and high blood sugar.

Analyses of these five individual components of metabolic syndrome revealed that loud snoring significantly predicted the development of high blood sugar and low HDL cholesterol. Difficulty falling asleep and unrefreshing sleep did not predict any of the individual metabolic abnormalities.

The study involved 812 participants in Heart SCORE, an ongoing community-based study of adults between 45 and 74 years of age. Individuals who were classified as having metabolic syndrome or diabetes at baseline were excluded from the analyses. During the three-year follow-up period, 14 percent of participants developed metabolic syndrome.

“Our results show that the risk of developing metabolic syndrome over a three-year follow-up period was more than two times higher in adults who reported frequent loud snoring,” noted Dr. Troxel. “This risk also was increased by 80 percent in adults who reported having difficulty falling asleep and by 70 percent in those who reported that their sleep was unrefreshing.”

Further analysis showed that unrefreshing sleep was reduced to marginal significance with additional adjustment for loud snoring. However, both loud snoring and difficulty falling asleep remained significant independent predictors of metabolic syndrome. “We believe these results emphasize the importance of screening for common sleep complaints in routine clinical practice,” added Dr. Troxel. Loud snoring continued to predict the development of metabolic syndrome even after accounting for the number of metabolic risk factors present at baseline. Dr. Troxel suggests that these findings “may implicate loud snoring as a causal risk factor for adverse cardiovascular and metabolic changes.”

Co-authors of the study include Daniel J. Buysse, M.D., Martica Hall, Ph.D., Karen A. Matthews, Ph.D., Patrick J. Strollo, M.D., Oliver Drumheller, Ed.D., R.R.T., and Steven E. Reis, M.D. (principal investigator of the parent study), all from the University of Pittsburgh School of Medicine; and Kevin E. Kip, Ph.D., from the College of Nursing at the University of South Florida.

The study is supported by funding provided by the Commonwealth of Pennsylvania Department of Health; the National Institutes of Health; the National Heart, Lung, and Blood Institute; and the Clinical & Translational Science Awards of the National Institutes of Health.

About the University of Pittsburgh School of Medicine

As one of the nation’s leading academic centers for biomedical research, the University of Pittsburgh School of Medicine integrates advanced technology with basic science across a broad range of disciplines in a continuous quest to harness the power of new knowledge and improve the human condition. Driven mainly by the School of Medicine and its affiliates, Pitt has ranked among the top 10 recipients of funding from the National Institutes of Health since 1997 and now ranks fifth in the nation, according to NIH data for 2008 (the most recent year for which the data are final).

Likewise, the School of Medicine is equally committed to advancing the quality and strength of its medical and graduate education programs, for which it is recognized as an innovative leader, and to training highly skilled, compassionate clinicians and creative scientists well-equipped to engage in world-class research. The School of Medicine is the academic partner of UPMC, which has collaborated with the University to raise the standard of medical excellence in Pittsburgh and to position health care as a driving force behind the region’s economy. For more information about the School of Medicine, see

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