Toronto (March 12, 2008) - Chronic sleep disruption can cause heart and kidney disease, researchers at the Peter Munk Cardiac Centre of the Toronto General Hospital have discovered.

"Disrupted circadian rhythms have a devastating effect on the heart, kidney and possibly other organs," says Dr. Michael Sole, Cardiologist and founding director of the Peter Munk Cardiac Centre and Professor of Medicine and Physiology at the University of Toronto. "This is the first study of its kind to demonstrate that sleep cycle disruption actually causes heart and kidney disease."

In the study entitled, "Circadian rhythm disorganization produces profound cardiovascular and renal disease in hamsters," published in the April edition of the American Journal of Physiology- Regulatory, Integrative and Comparative Physiology, researchers found when internal biological clocks in hamsters are out of sync with external rhythm regulators (i.e. light/dark), the heart becomes damaged and enlarged (cardiomyopathy), and the kidney tubules sustain significant scarring.

The importance of circadian rhythms - the body's "hard-wired" 24-hour sleep-wake cycle, is well understood in the regulation of cardiovascular physiology. Earlier studies by Dr. Sole and his colleagues suggested that renewal of cardiovascular tissues predominantly occur during sleep; therefore sleep interruption can directly damage organs.

Trans-meridian flight crews, truck drivers and shift workers often suffer from sleep cycle disruption due to the nature of their jobs. Although the medical focus has largely been on neuropsychological factors such as task performance and memory, these groups are known to have a higher than average prevalence of cardiovascular disease.

"Shift workers and flight-crews might want to consider these findings when scheduling work time," suggests Dr. Sole, adding that these workers could try to maintain a constant working schedule for one month or more, allowing the body to readjust its clock to external cues. Dr. Sole also notes that some hospitals, particularly in intensive care units, still use multi-bedded rooms, continually disrupting sleep-wake cycles in the critically ill.

The Heart and Stroke Foundation and the A. Ephraim and Shirley Diamond Cardiomyopathy Research Fund funded this study.

About the Heart and Stroke Foundation

The Heart and Stroke Foundation, a volunteer-based health charity, leads in eliminating heart disease and stroke and reducing their impact through the advancement of research and its application, the promotion of healthy living, and advocacy.

About Peter Munk Cardiac Centre

The Peter Munk Cardiac Centre is the premier cardiac centre in Canada. Since it opened in 1997, the Centre has saved and improved the lives of cardiac patients from around the world. Each year, approximately 17,000 patients receive the innovative and compassionate care from the Peter Munk Cardiac Centre multidisciplinary heart team. In addition, the Peter Munk Cardiac Centre trains more cardiologists and cardiovascular surgeons than any hospital in Canada. The Centre is based at Toronto General Hospital – a member of University Health Network, which also includes Toronto Western Hospital and Princess Margaret Hospital. All three are research hospitals affiliated with the University of Toronto.

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