How to assess circadian rhythm in humans: a review of literature.

It is well known that seizures of some types of epilepsy tend to occur in patterns. The circadian rhythm may play a significant role in this phenomenon. In animal studies it has been found that seizures in experimental partial epilepsy are probably under the influence of the biological clock. In this review an introduction to the influence of the human circadian rhythm in epilepsy is given. Furthermore, the methodology of measuring the circadian rhythm in humans is explored. An overview of widely used methods includes protocols used to desynchronize circadian rhythm, and sleep-wake and biological markers such as the dim light melatonin onset, core body temperature, and cortisol that are employed to determine the phase of the circadian rhythm. Finally, the use of sleep parameters, actigraphy, and questionnaires is discussed. These are also important in assessment of the circadian rhythm.