On conditions of occurrence of seasonal disorders in human circannual and circadian rhythm

Analytical expressions are proposed that establish the interrelation of calendar dates of onset and cessation, and also the durations of seasonal disorders of human circannual and circadian rhythms with the geographic coordinates of the reference point on the terrestrial surface and the corresponding altitude angle of the Sun. The obtained theoretical results correspond to the data of independent experimental research on circannual and circadian rhythm and supplement them. The use of the results of work will allow raising the efficacy of measures on prevention and suppression of human circannual and circadian rhythm disorders. © 2014 Pleiades Publishing, Inc.