Edited by: Prof Shigekazu Higuchi
Sleep and circadian rhythms are fundamental phenomena in biological organisms. Research indicates that lack of sleep and disruptions in circadian rhythms correlate with poor mental and physical health. In modern society, humans live surrounded by various factors that disrupt our sleep and circadian rhythms, such as the internationalization of business, the increasing 24-hour nature of commercial services, the ease of accessibility of information, longer and more unsocial working hours. In this special issue in Journal of Physiological Anthropology we investigate how human sleep and circadian rhythms are affected by our modern environment? Can our bodies adapt to these changes, it appears that, at least in certain societies and populations, sleep and circadian rhythms have not been able to adapt.
There has been a great deal of research in recent years in the field of human sleep and circadian rhythm, both at the gene and the physiological level. Individual differences in sleep and circadian rhythms have been associated with some clock gene polymorphisms. The impact of environmental factors cannot be ignored. Light in particular is an important synchronizer for circadian rhythms, and has been shown to be effective in the treatment of circadian rhythm disorder and seasonal affective disorder. However, light can also be detrimental, excessive night time exposure is a possible risk factor for cancer in shift workers. Other environmental factors such as temperature, whilst not acting directly on the circadian pacemaker, could be an important factor in determining the quality of sleep.
In physiological anthropology, variations in the physiological states and responses are considered substantive. It is therefore necessary to clarify the mechanisms and factors that give rise to these variations. It is also important to explain the physiological or biological significance of these variations from the standpoint of adaptation. Sleep and circadian rhythm research has been moving forward on many fronts, from the molecular level to the population level, and from research done in the lab to research done in the field. The goal of physiological anthropology is to understand these findings in the context of adaptation, in order to obtain a clearer understanding of the essential nature of man.