Consequently, the individual’s sleep pattern becomes desynchronized from the circadian system

and, in the case of shift workers, daytime sleep duration is short, sleep efficiency is poor, and night-time waking alertness and performance are impaired,9 accounting for the high incidence of accidents and injuries experienced by nightshift workers.10 Other functions also become desynchronized Inhibitors,research,lifescience,medical under such conditions, for example, postprandial metabolism. When meals are taken during the biological night, they cannot be metabolized as efficiently as when eaten during the day, and Inhibitors,research,lifescience,medical consequently postprandial levels of glucose, Insulin, and fats are elevated.11-13 In the long term, the regular Impairment of metabolism Induced over years of shiftwork may lead to chronically elevated clrculating levels of Insulin and fat, and may increase the risk of developing Insulin resistance, diabetes, or cardiovascular disease.14 Gastrointestinal discomfort is also a common complaint In jet lag,15 most likely due to the temporal misalignment of circadian oscillators In peripheral tissues (eg, the liver, kidney, Inhibitors,research,lifescience,medical esophagus, and stomach) that have recently been Identified (for review

see ref 16). The potential Inhibitors,research,lifescience,medical GSK126 in vitro Importance of light In human circadian entrainment was first explored in cave experiments, where investigators measured rhythms In physiology and behavior when shielded from the solar day (although dim artificial light was generally available).17,18 These studies Indicated that the circadian Inhibitors,research,lifescience,medical pacemaker did not oscillate

exactly on a 24-hour day, but had a circadian period (x) that was on average slightly longer than 24 hours. Studies of subjects kept in temporal Isolation,19 In dim Hght-dark cycles,20,21 or on very long (eg, 28-h, 30-h, 42.85 h) or very short (eg, 11-h, much 20-h) day-lengths outside the range of entrainment of the biological clock have also shown that the period of the circadian clock Is not exactly 24 hours In humans (average -24.2 h)22,23 similarly to that In other mammals. Under such nonentrained conditions, the rhythms controlled by the circadian system ”free-run“ at the endogenous period of the biological clock. For example, If a person’s nonentrained period Is 24.5 h, the sleep-wake cycle and other rhythms will also cycle with a period of 24.5 h and the subject will therefore go to sleep 0.5 hours later each day, when measured using the 24hour clock (see below).