This is not medical advice. It does not diagnose, treat, or replace a clinician.
Sources
Each item is a paper, a guideline, an official table, or a public health page. The finding line is what we are willing to say from it.
Last reviewed: 18 October 2026.
2026-10-18
Strong · Free
Advancing circadian rhythms before eastward flight: a strategy to prevent or reduce jet lag
Lab study: shifting sleep 1 hour earlier each day for 3 days, plus morning bright light, moved the body clock earlier by a median 1.4 hours. A 2-hour daily shift was not clearly better, and people had trouble falling asleep by day 3.
Open the sourceStrong · Free
Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep
Lab study: a 1-hour-earlier schedule for 3 days, with morning light and afternoon melatonin, moved the clock about 1.7–2.4 hours. The first light after waking mattered most. Melatonin is a medicine in Hong Kong; this plan does not use it.
Open the sourceModerate · Free
Entrainment of the human circadian clock to the natural light-dark cycle
Small camping study (about 8 people): a week of natural light moved the clock about 2 hours earlier. Sleep times moved less, about 1.2 hours.
Open the sourceModerate · Free
Circadian entrainment to the natural light-dark cycle across seasons and the weekend
A weekend of camping moved melatonin onset about 1.4 hours earlier. A usual modern weekend moved the clock about 1 hour later.
Open the sourceStrong · Free
A phase response curve to single bright light pulses in human subjects
Lab study: light in the hours after the body-temperature low moves the clock earlier. Light before that point moves it later. A jump that is too large can put 05:00 light in the delay zone.
Open the sourceModerate · Free
Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults
Expert consensus: daytime light at the eye of at least about 250 melanopic lux, evening light at or below about 10 melanopic lux in the 3 hours before bed, and no more than about 1 lux while sleeping.
Open the sourceModerate · Free
Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans
Room light before bed suppressed melatonin and shortened it, compared with dim light. This is a lab finding about room light, not a test of ordinary phone use.
Open the sourceModerate · Free
Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness
Lab study: reading on a light-emitting e-reader for 4 hours in the evening delayed the clock and reduced next-morning alertness, compared with a paper book.
Open the sourceModerate · Paywalled
Light therapy for seasonal and nonseasonal depression: efficacy, protocol, safety, and side effects
Review of light therapy: bright light can provoke hypomania, and eye disease or light-sensitising medicines need a clinician before a light box. This plan does not prescribe a light box.
Open the sourceStrong · Free
Times of sunrise and sunset in Hong Kong, 2026
Official 2026 tables: Hong Kong sunrise runs from about 05:38 in June to about 07:03 in January. At 05:00 there is no daylight. Morning light has to start with a lamp, then outdoors after sunrise.
Open the sourceStrong · Paywalled
National Sleep Foundation’s sleep time duration recommendations: methodology and results summary
National Sleep Foundation ranges: adults 18–64 are advised 7–9 hours, adults 65 and over 7–8 hours, and teens 14–17 are advised 8–10 hours. The journal article is paywalled; the link is the NSF summary.
Open the sourceStrong · Free
Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society
Consensus: adults should sleep 7 or more hours a night on a regular basis.
Open the sourceStrong · Free
Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine
Consensus: teens 13–18 are advised to sleep 8–10 hours. This plan is not for people under 18.
Open the sourceStrong · Free
The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation
Lab study: 6 hours of sleep a night for 14 days caused thinking deficits similar to 1–2 nights without sleep, and people did not notice how impaired they were.
Open the sourceModerate · Free
Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep
Lab study: catch-up sleep on weekends did not undo the metabolic harm of short weeknights.
Open the sourceStrong · Free
Report of Population Health Survey 2014/15
Official survey of people aged 15 and over (about 12,000, 2014/15): average sleep was 7.0 hours a day, 36.1% slept under 7 hours, and 48% reported some sleep disturbance in the past 30 days. Self-report.
Open the sourceStrong · Free
The effect of caffeine on subsequent sleep: a systematic review and meta-analysis
Meta-analysis of 24 studies: caffeine cut total sleep by about 45 minutes. To avoid that loss, a regular coffee (107 mg) needed about 8.8 hours before bed. A cup of black tea showed no cutoff.
Open the sourceStrong · Paywalled
Alcohol and sleep I: effects on normal sleep
Review of sleep-lab studies: alcohol can make it easier to fall asleep, then fragments the second half of the night and reduces REM at moderate and high doses.
Open the sourceStrong · Free
Advancing circadian rhythms before eastward flight: a strategy to prevent or reduce jet lag
Lab study: shifting sleep 1 hour earlier each day for 3 days, plus morning bright light, moved the body clock earlier by a median 1.4 hours. A 2-hour daily shift was not clearly better, and people had trouble falling asleep by day 3.
Open the sourceStrong · Free
Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep
Lab study: a 1-hour-earlier schedule for 3 days, with morning light and afternoon melatonin, moved the clock about 1.7–2.4 hours. The first light after waking mattered most. Melatonin is a medicine in Hong Kong; this plan does not use it.
Open the sourceModerate · Free
Resetting the late timing of ‘night owls’ has a positive impact on mental health and performance
Small study (22 people, 12 in the program): night owls moved wake time about 1.9 hours earlier in 3 weeks without losing sleep. Mood scores improved in that healthy group. This is not evidence about people already in treatment.
Open the sourceModerate · Free
Circadian entrainment to the natural light-dark cycle across seasons and the weekend
A weekend of camping moved melatonin onset about 1.4 hours earlier. A usual modern weekend moved the clock about 1 hour later.
Open the sourceStrong · Free
Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg
Lab study: 0.5 mg melatonin worked best 2–4 hours before melatonin onset, not at bedtime, and moved the clock about 1.5 hours over 3 days. This plan gives no dose. In Hong Kong, ask a doctor or pharmacist.
Open the sourceStrong · Free
Clinical practice guideline for the treatment of intrinsic circadian rhythm sleep-wake disorders
American Academy of Sleep Medicine guideline on circadian rhythm sleep-wake disorders. Timed melatonin has a weak recommendation for delayed sleep-wake phase disorder. Shift work needs clinical care, not this plan.
Open the sourceModerate · Free
Human circadian phase-response curves for exercise
One lab study, about 100 people: 1 hour of moderate exercise at 07:00 or 13:00–16:00 moved the clock earlier (about 0.9 hours at 07:00). Exercise at 19:00–22:00 moved it later.
Open the sourceModerate · Paywalled
Effects of evening exercise on sleep in healthy participants: a systematic review and meta-analysis
Meta-analysis: evening exercise generally did not harm sleep, except vigorous exercise ending less than 1 hour before bed.
Open the sourceModerate · Paywalled
Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis
Meta-analysis of small studies: a warm shower or bath (40–42.5°C, at least 10 minutes) 1–2 hours before bed helped people fall asleep faster and rate sleep better.
Open the sourceModerate · Free
Effects of thermal environment on sleep and circadian rhythm
Lab work and review: humid heat increases waking and cuts deep and REM sleep, especially early in the night. Popular thermostat ranges are not backed by good trials, so this plan does not quote one.
Open the sourceWeak · Free
Meal timing regulates the human circadian system
Lab study: moving meals 5 hours later shifted glucose rhythms, not the melatonin clock. Meal timing alone has not been shown to move the master clock.
Open the sourceStrong · Free
Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline
Guideline: multi-part CBT-I is strongly recommended for chronic insomnia. Stimulus control has a conditional recommendation. Sleep-hygiene education on its own is suggested against. Tips here are not a treatment.
Open the sourceModerate · Free
Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep
Lab study: catch-up sleep on weekends did not undo the metabolic harm of short weeknights.
Open the sourceModerate · Paywalled
Social jetlag: misalignment of biological and social time
The gap between workday and free-day sleep timing is called social jet lag. The paper names the pattern; it does not test this plan’s 60-minute weekend allowance. That allowance is our heuristic.
Open the sourceModerate · Free
Bedtime procrastination: introducing a new area of procrastination
Cross-sectional study: going to bed later than intended, with nothing forcing it, went with less sleep and more daytime fatigue. “Revenge bedtime” is a popular phrase, not the research term.
Open the sourceStrong · Free
A marker for the end of adolescence
Large observational sample (about 25,000): chronotype is latest around age 20 and gets earlier after that. No study here compared how fast different ages can move earlier.
Open the sourceModerate · Paywalled
Association of intrinsic circadian period with morningness–eveningness, usual wake time, and circadian phase
Later types tend to have a longer internal day, so the clock drifts later and slips back most easily on free days.
Open the sourceModerate · Paywalled
A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms
The Morningness-Eveningness Questionnaire has 19 items. The five questions in this plan are only inspired by that idea. They are not the questionnaire and not a diagnosis.
Open the sourceModerate · Free
Resetting the late timing of ‘night owls’ has a positive impact on mental health and performance
Small study (22 people, 12 in the program): night owls moved wake time about 1.9 hours earlier in 3 weeks without losing sleep. Mood scores improved in that healthy group. This is not evidence about people already in treatment.
Open the sourceModerate · Free
Human circadian phase-response curves for exercise
One lab study, about 100 people: 1 hour of moderate exercise at 07:00 or 13:00–16:00 moved the clock earlier (about 0.9 hours at 07:00). Exercise at 19:00–22:00 moved it later.
Open the sourceStrong · Free
The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation
Lab study: 6 hours of sleep a night for 14 days caused thinking deficits similar to 1–2 nights without sleep, and people did not notice how impaired they were.
Open the sourceWeak · Free
Is snoozing losing? Why intermittent morning alarms are used and how they affect sleep, cognition, cortisol, and mood
In habitual snoozers, 30 minutes of snoozing cost about 6 minutes of sleep and did not impair thinking on waking. Evidence is mixed: see Ogawa 2022.
Open the sourceWeak · Free
Effects of using a snooze alarm on sleep inertia after morning awakening
Small study in Japan: snoozing prolonged drowsiness after waking. Together with Sundelin 2023, the evidence on snoozing is mixed.
Open the sourceModerate · Free
Sleep inertia: current insights
Review: grogginess on waking is worst in the first 15–30 minutes, and worse with sleep loss, waking at the clock’s low point, or waking from deep sleep.
Open the sourceModerate · Free
How people wake up is associated with previous night’s sleep together with physical activity and food intake
Observational study (833 people): morning alertness rose with more or better sleep, more activity the day before, and breakfast. It did not depend on the genetics they measured.
Open the sourceStrong · Free
Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg
Lab study: 0.5 mg melatonin worked best 2–4 hours before melatonin onset, not at bedtime, and moved the clock about 1.5 hours over 3 days. This plan gives no dose. In Hong Kong, ask a doctor or pharmacist.
Open the sourceStrong · Free
Clinical practice guideline for the treatment of intrinsic circadian rhythm sleep-wake disorders
American Academy of Sleep Medicine guideline on circadian rhythm sleep-wake disorders. Timed melatonin has a weak recommendation for delayed sleep-wake phase disorder. Shift work needs clinical care, not this plan.
Open the sourceStrong · Free
Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline
Guideline: multi-part CBT-I is strongly recommended for chronic insomnia. Stimulus control has a conditional recommendation. Sleep-hygiene education on its own is suggested against. Tips here are not a treatment.
Open the sourceStrong · Free
Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine
Consensus: teens 13–18 are advised to sleep 8–10 hours. This plan is not for people under 18.
Open the sourceStrong · Paywalled
School start times for adolescents
Policy statement: adolescents are biologically later, and the Academy advises against school schedules that ignore that. This plan is not for minors.
Open the sourceModerate · Paywalled
STOP questionnaire: a tool to screen patients for obstructive sleep apnea
The STOP questions are a validated screen for when to refer someone for possible obstructive sleep apnoea. They are not a diagnosis.
Open the sourceModerate · Paywalled
Sleep reduction as a final common pathway in the genesis of mania
Sleep loss can be a pathway into mania. This plan does not proceed if someone has bipolar disorder or a past episode of mania.
Open the sourceModerate · Paywalled
Light therapy for seasonal and nonseasonal depression: efficacy, protocol, safety, and side effects
Review of light therapy: bright light can provoke hypomania, and eye disease or light-sensitising medicines need a clinician before a light box. This plan does not prescribe a light box.
Open the sourceWeak · Free
Insomnia
NHS public page on insomnia and when to see a GP. It is a health-service overview, not a trial. Reviewed for this feature on 18 Oct 2026.
Open the sourceWeak · Free
Sleep apnoea
NHS public page on sleep apnoea. It is a health-service overview, not a diagnosis. Reviewed for this feature on 18 Oct 2026.
Open the sourceWeak · Free
Consumer FAQ
Hong Kong Drug Office consumer FAQ. The exact legal class of melatonin was not confirmed in the 18 Oct 2026 research pass, so this plan gives no dose and says to ask a doctor or pharmacist.
Open the sourceModerate · Free
Effects of thermal environment on sleep and circadian rhythm
Lab work and review: humid heat increases waking and cuts deep and REM sleep, especially early in the night. Popular thermostat ranges are not backed by good trials, so this plan does not quote one.
Open the sourceStrong · Free
Report of Population Health Survey 2014/15
Official survey of people aged 15 and over (about 12,000, 2014/15): average sleep was 7.0 hours a day, 36.1% slept under 7 hours, and 48% reported some sleep disturbance in the past 30 days. Self-report.
Open the sourceStrong · Free
Who reports insufficient and disturbed sleep? Results from a representative population-based health survey in Hong Kong
Open-access analysis of the same 2014/15 Department of Health survey. It does not add a newer representative bedtime study.
Open the sourceWeak · Free
Survey on sleep time of Hong Kong people
2003 phone poll of working adults aged 25–55: the most common workday bedtime was 23:00–24:00 (38.7%), another 21% were after midnight, average sleep was 6.0 hours, and 62% wanted extra weekend sleep. This is old.
Open the sourceStrong · Free
2024 Report on Annual Earnings and Hours Survey
Official 2024 figures: median weekly hours were 43.4 overall and 44.3 for full-time workers. Food and beverage median was 54 hours; security, 59. Long shifts may not fit a 21:30 bedtime.
Open the sourceStrong · Free
Times of sunrise and sunset in Hong Kong, 2026
Official 2026 tables: Hong Kong sunrise runs from about 05:38 in June to about 07:03 in January. At 05:00 there is no daylight. Morning light has to start with a lamp, then outdoors after sunrise.
Open the sourceStrong · Free
Climatological normals for Hong Kong, 1991–2020
1991–2020 normals: summer (June–August) mean temperature about 28.6°C and relative humidity about 81%. Annual relative humidity is about 78%.
Open the sourceWeak · Free
Consumer FAQ
Hong Kong Drug Office consumer FAQ. The exact legal class of melatonin was not confirmed in the 18 Oct 2026 research pass, so this plan gives no dose and says to ask a doctor or pharmacist.
Open the source