Chronotype and Its Relation to Healthy Aging

Chronotype is individuals’ endogenous circadian phase which is obvious through preference for scheduling timings of sleep–wake, physical or mental activities at behavior level, as well as differences in circadian phase in biological variables (e.g., body temperature or serum melatonin concentration). Three different chronotypes prevail in human population viz. morning, evening and intermediate types with respective proclivities. Along with the impact of environment and societal factors, chronotype behavioral trait also has genetic underpinnings. Besides, age and gender also can modulate this trait. Humans are diurnally active by nature. To enhance the longevity and reduce the risk of mortality in dawn and night time during primitive time when human and animals shared a common space, different chronotypes evolved with evolution. However, modern lifestyle with availability of 24 h of artificial light (emitting blue light) has encroached into the night period causing thereby, delayed sleep–wake timings, reduced sleep quality and efficiency. This has serious consequences in terms of limiting the synchronization of biological clock with morning sunlight leading to circadian desynchronization. Thus, emergence of evening chronotypes with advancement in technologies has also shown that these “night owl” people are at increased risk of circadian misalignment that is apparent through poor health consequences, e.g., increased odds of sleep, metabolic and cardiovascular disorder, respiratory problems, psychiatric ailments, unhealthy habits and social maladjustment. Thus, this chapter discusses about the chronotype, its distribution, assessment, determinants and moderators, and recommended strategies to maintain healthy chronotype and adopt healthy lifestyle to ensure healthy aging.