Interruption of the normal sleep-wake cycle may risk serious health consequences.

Evidence is increasing that night-shift work can raise the risk of cardiovascular disease. In a randomized, crossover trial 30 healthy Austrian physicians submitted to a battery of tests to determine the effects of a prolonged workday on heart rate, blood pressure, cardiac rhythm, and biochemical markers. When compared with routine work days, those with prolonged workdays experienced significantly higher diastolic blood pressure, more premature ventricular contractions, and higher levels of biomarkers of stress.