[The effect of natural daylight on human regulation]

Day-light stimulates the endocrine glands about the biological clock. The annual variation of day-length and brightness lead to uni-modal annual rhythms of morbidity, mortality and physiological parameters too. Meteoropathological disturbances show an antagonistic influence of interdiurnal variations of day-light. In summer-time the seldom dark days and in winter-time the seldom bright days induce such phenomena. Another antagonistic influence of day-light is reflected by a bi-modal annual and by an about 14-days-rhythm. Upper-waves of annual rhythms with frequencies between 7 and 35 days can be synchronized by strong interdiurnal changes of day-light for man living in the same geographical region. The results as a whole may be explained by interdiurnal and seasonal modifications of human diurnal rhythms in form of changing phase-differences of two or more circadian oscillators.