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Working nights is bad for the heart

(Vienna, 26-04-2016) Working at night is unhealthy for the heart and increases the risk of sustaining coronary heart disease, meaning a disease of the coronary arteries. This is the result of a current, and one of the largest American cooperation studies under the management of Eva Schernhammer of the epidemiology division of MedUni Wien, which was published in the top journal JAMA today. First author is Celine Vetter of Harvard University in Boston.

Approximately 240,000 nurses, who were working day and night shifts at irregular intervals for around five years, were examined in the USA. The pivotal result: nurses, who also work nights for more than ten years have a 15 - 18% greater risk of developing a coronary heart disease than those working without nightshifts. However, the risk is also increases significantly after only five years of nightshift.

This also applies for those women who were classified as healthy and had no illnesses prior to entering the nightshift rhythm. Also in previous studies, MedUni Vienna epidemiologist from the Centre for Public Health was able to demonstrate with her research group at Harvard Medical School that - among other - also the breast and bowel cancer risk, the risk for diabetes or hypertension as well as for adiposity is elevated in nightshift workers.

At the same time, the researchers of the Centre for Public Health of MedUni Vienna were able to prove that the risk for coronary heart disease decreases continuously if the women change to a job exclusively with dayshifts or retire.

"Mini-Jet-Lag" at changes from night to dayshift
For this reason, the scientists recommend generally to reconsider the duty rosters for the nightshift and to offer preventative, company-internal health checks, but possibly also consider the "Chrono type" of the employee during the hiring process. Schernhammer: "Approximately 15% of the population are evening types and 20 % or more are morning types. The rest are mixed types." Sensitive types could suffer a "mini jet lag" along with sleeping disorders at a quick change between night and dayshifts.

About coronary heart disease
With annually approximately 17 million fatalities worldwide, in Europe approx. four million, coronary heart disease represents the most frequent cause of death. In the USA, every fourth death is due to a coronary disease. Coronary heart disease, which is a chronic illness, causes deposits up to a blockage in the vessels. The consequence: the circulation is impaired; the oxygen supply of the cardiac muscles deteriorates. An imbalance between the need and supply of oxygen is created (ischaemia). With the advance of the disease, the probability of cardiac arrhythmia, cardiac insufficiency, infraction and sudden cardiac death is increased.

Service: JAMA
"Association between rotating night shift work and risk of coronary heart disease among women" C. Vetter, E. Devore, L. Wegrzyn, J. Massa, F. Speizer, I. Kawachi, B. Rosner, M. Stampfer, E. Schernhammer. JAMA, April 26, 2016.