The influence of light on human regulation in relation to social factors

Abstract

Abstract In eight long‐term examination series it could be shown that the efficiency of healing processes during summer months is favoured significantly by the increase in the number of bright days in the curing period. Three other series of observations give evidence of the fact that meteoropatholo‐gical disturbances augment with the increase of clouded, dark days in summer and less cloudy, bright days in winter. Variations of the diurnal rhythm imply that from winter to summer the ergo‐tropic phase in the course of human regulation anticipates by 1 to 2 hrs and ends with a delay of about 1 hr in the evening. These phase shifts are superposed by shifts of 3 or 4 hrs with a rhythm of about 35 days. By means of long‐term observations of various physiological parameters it is possible to prove the existence of 7‐day and 35‐day rhythms which are characterized, especially the latter one, by a high degree of synchronization for several subjects. From daily observations of the day rhythm of several physiological functions some information can be obtained regarding the discordant behaviour reversal of reaction within two half‐periods each lasting about 7 ... 10 days. The results presented make us presume that it is the daylight which acts as a first‐order Zeitgeber for the human organism. The changes of daylight intensity and of length of daylight, dependent on the seasons, stimulate the organism to adaptive reactions which are reflected by a single yearly course and a superimposed 7‐day and 35‐day rhythm, respectively, and for which the different meteorological conditions influencing the length of daylight and intensity of light act as a modifying factor with respect to phase and amplitude.