What does the research say about chronotype?

Chronotype is the term used to describe an individual's natural preference for the timing of sleep and activity across the 24-hour day. It is often referred to as morningness–eveningness, and is classified as a behavioural manifestation of underlying circadian rhythms. The evidence block does not provide a sequence, formula, or molecular weight for chronotype, as it is not a single molecular entity but a complex trait. The work centres on the circadian system, which regulates biological functions and varies between individuals, creating chronotypes [4].

Research into chronotype spans several areas, including its interaction with exercise, sleep disorders, and metabolic health. Studies often compare morning-type and evening-type individuals, or examine how aligning interventions with chronotype may affect outcomes. The following sections summarise findings from registered clinical trials and reviews.

Research Studies

Chronotype and exercise timing in prediabetes

A clinical trial is investigating whether exercising at the right time of day, based on a person's natural body clock, leads to greater health benefits in people living with prediabetes. The study aims to determine whether a single session of exercise in the morning or in the evening affects how the body handles sugar differently in adults with prediabetes who have an extreme natural body clock. The trial compares three conditions—no-exercise, morning exercise, and evening exercise—within the same participant, with each condition tested on a different day and at least 14 days between test days [1].

Chronotype and cognitive behavioural therapy for insomnia in adolescents with ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by persistent inattention, hyperactivity, and impulsivity. In adolescents and young people, ADHD is commonly accompanied by insomnia and circadian delay. These co-occurring sleep and circadian disturbances may negatively affect daytime functioning and overall clinical outcomes. Although cognitive behavioural therapy for insomnia (CBT-I) is considered the first-line treatment for insomnia, and bright light therapy may help address circadian issues, their efficacy in adolescents with ADHD and comorbid insomnia and eveningness remains unexplored. A study aims to evaluate whether CBT-I, with or without bright light therapy, is effective in this population [2].

Chronotype and exercise timing in athletes and physically active adults

A structured narrative review synthesised evidence on morning versus afternoon/evening training in athletes and physically active adults, integrating performance outcomes with internal load, autonomic recovery, sleep interaction, and downstream physiological stress. Acute evidence generally supports superior late-afternoon or early-evening performance, particularly for neuromuscular tasks, whereas chronic training studies do not indicate a universal optimal training time [3].

Chronotype and nocturia in women with urinary incontinence

Urinary incontinence (UI) is the involuntary leakage of urine that negatively affects individuals socially, physically, and psychologically, leading to a decreased quality of life. Nocturia, which is often seen alongside UI, has similar adverse effects. Nocturia refers to the number of urinations during the main sleep period, and it should be accompanied by the intention to fall back asleep after waking up. Nocturia can arise from factors such as sleep disorders and circadian rhythm disturbances. The circadian rhythm regulates the body's biological functions, and this rhythm varies from person to person, creating chronotypes. There is a strong relationship between sleep and chronotype in this context [4].

Chronotype and metabolic signatures of sleep health in stroke risk

A prospective cohort study included 200,729 UK Biobank participants and investigated whether a nuclear magnetic resonance-derived metabolic signature mediates the association between healthy sleep and lower stroke risk. The study reported that healthy sleep is associated with lower stroke risk, but the underlying metabolic mechanisms remain poorly understood. This finding is reported in a reference-only source and is not specific to chronotype [5].

Comparison of study designs

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Sources

• [1] Exercise, Chronotype, and Prediabetes
• [2] Efficacy of Cognitive Behavioural Therapy for Insomnia and Bright Light Therapy in Adolescents With ADHD, Insomnia, and Evening Chronotype
• [3] Exercise Timing in Sport: Molecular and Physiological Mechanisms Linking Performance, Recovery, and Biological Cost.
• [4] Examination of the Effect of Nocturia on Pelvic Floor Symptoms, Sleep Parameters and Quality of Life in Women With Urinary Incontinence
• [5] Metabolic signatures of sleep health and stroke risk: A prospective cohort study with mediation analysis.