Sleep Foundation:

Chronotypes are the natural preferences of the body for wakefulness and sleep, influenced by genetics and circadian rhythms. They affect sleep, performance, and activity throughout the day. Adapting to one's natural chronotype improves sleep quality, energy, and mood. Chronotypes, such as being an early bird or a night owl, also influence appetite, exercise, and body temperature, reflecting alertness and sleepiness at different times (Sleep Foundation).

Chronotype variation is linked to genetics, age, and other factors, possibly including geographical location due to daylight changes. Understanding one's chronotype can enhance sleep quality and life quality (Sleep Foundation).

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Scientific Reports:

Modern lifestyles, characterized by extended indoor stays with modest light exposure and late-evening light exposure, influence chronotypes. Elevated daytime light reduces chronotype differences and protects against extreme eveningness, associated with better health and performance. However, typical evening light exposure at home leads to later chronotypes, increasing sleep and circadian problems. Late chronotypes report lower sleep quality, higher chronic fatigue, emotional problems, metabolic disorders, and higher substance use risks (Scientific Reports).

Evening types (later chronotypes) not sleeping in sync with their natural tendency have been linked to higher morbidity and mortality. A study in the UK Biobank cohort found that greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of comorbidities, including psychological, diabetes, neurological, gastrointestinal, and respiratory disorders. Additionally, there was a small increased risk of all-cause mortality and cardiovascular disease mortality in those with greater eveningness (PubMed).

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While I was unable to find specific health recommendation guidelines on sleeping in synchrony with natural chronotypes, the information from these sources highlights the importance of aligning sleep with one's natural chronotype to maintain health and reduce the risk of morbidity and mortality.

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Bibliography​

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• PubMed. " Genetic Basis of Chronotype in Humans: Insights From Three Landmark GWAS" [Online]. Available: https://pubmed.ncbi.nlm.nih.gov/28364486/

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• PubMed. "Associations between chronotype, morbidity and mortality in the UK Biobank cohort." [Online]. Available: https://pubmed.ncbi.nlm.nih.gov/29642757/