Morningness-eveningness preference, sleep quality and behavioral sleep patterns in humans - a mini review

The sleep requirement of humans varies as a function of the country they live in, and their chronotype, gender, ethnicity, physiological state, and lifestyle. An interaction between the circadian clock (process C) and the sleep-wake homeostasis (process S) regulates sleep in humans. The Suprachiasmatic nuclei (SCN) - the master clock, measures the length of the solar day and through appropriate neuroendocrine mechanisms promotes sleep in the night. In this mini-review, we made an attempt to summarize findings of earlier studies dealing with the distribution pattern of chronotypes, sleep quality, and behavioral sleep patterns in human populations. The review is based on 203 relevant papers that we picked up from the databases, such as PubMed, Scopus, and Google Scholar. The review reveals the paucity of information on sleep behavior in humans in densely populated countries, like China and India. In addition, a clear message emerged from the review of the literature, i.e. the studies on the distribution of chronotypes and their problems associated with sleep quality, the behavioral sleep pattern, and diseases are critically limited and are far from complete. We recommend that this is the area that needs to be investigated extensively and intensively.