In short
In a high pressure job the single most measurable thing going wrong is usually sleep, and it is rarely asked about.
- Seven hours minimum for adults aged 18 to 60. About a third of adults get less.
- Sleeping much longer at weekends is the clearest sign of chronic weekday sleep debt.
- Caffeine should stop about 8.8 hours before bed. It cuts total sleep by around 45 minutes on average.
In a randomised trial, extending sleep by 1.2 hours a night cut energy intake by 270 kcal a day and weight by 0.87 kg in two weeks, without anyone dieting.
Condition Overview
Why start with sleep?
Because it is quantifiable, it is nearly always the biggest deficit, and people almost never present with it. They present with fatigue, irritability, poor concentration and low motivation instead.
Those are the recognised symptoms of insufficient sleep, along with reduced vigilance, distractibility and restlessness. They are also, unhelpfully, exactly what burnout looks like.
How much sleep, honestly?
| 18 to 60 | Seven hours or more per night on a regular basis |
| 18 to 64 | Seven to nine hours per night |
| 65 and over | Seven to eight hours |
If you naturally need more, even seven to nine hours can be relatively insufficient for you. A genuine short sleeper gets under six hours and has no daytime symptoms at all, which is rare.
What is social jet lag?
The gap between your weekday and weekend sleep. A large increase at weekends is a strong indicator of chronic sleep deprivation caused by weekday obligations.
It is measurable from a two week sleep diary, which also gives sleep latency, ideally 15 to 20 minutes, and sleep efficiency, normally 85 per cent or more.
What is actually costing you sleep?
- Caffeine. On average it lengthens time to fall asleep by 9 minutes, adds 12 minutes of night waking and reduces total sleep by around 45 minutes. Coffee should stop about 8.8 hours before bed
- Alcohol. It shortens the time to fall asleep, then increases waking and light sleep in the second half of the night and lowers sleep quality
- Screens. Blue light suppresses melatonin, and phone use also simply delays bedtime
- Evening exercise. Training between 7 and 10 pm can delay sleep onset. Morning and early afternoon exercise advances it
Are sleep trackers useful?
Somewhat. They give reasonable total sleep time and add to the clinical picture, but their accuracy varies and they perform best in people who do not have a sleep problem.
People also over report their own sleep. In 615 adults, self reported duration correlated only modestly with objective measurement.
When to See a Doctor
- You sleep considerably longer at weekends than on weekdays
- Fatigue, irritability and poor concentration have become the normal state
- You rely on caffeine to function and alcohol to switch off
- Blood pressure or weight has drifted up over a couple of years
- You sit for most of the day and travel disrupts any routine you build
- Falling asleep while driving or at the wheel at traffic lights, which is an immediate safety issue
- Snoring with witnessed pauses in breathing, or waking unrefreshed after eight hours, which suggests sleep apnoea
- Persistent low mood, loss of interest, or thoughts of self harm, which need assessment now
How Dr. Felix Assesses This
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1
Actual sleep, not estimated sleep
Bedtime and rise time on weekdays and weekends, time in bed versus time asleep, night waking, naps, and whether sleep is refreshing. A two week sleep diary gives far more than a single question does.
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2
Separating short sleep from a sleep disorder
Unrefreshing sleep of adequate length points elsewhere: obstructive sleep apnoea, restless legs, insomnia, or a circadian problem. These need their own treatment and do not respond to going to bed earlier.
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3
The measurable inputs
Caffeine timing, alcohol intake, screen use before bed, exercise timing, and the sleep environment. Each has a specific evidence based adjustment rather than a general instruction.
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4
The physical consequences
Blood pressure, weight, lipids and glucose, because these are where sustained pressure shows up first and where improvement is measurable.
Treatment Options
CEO Health Assessment
Who does the doctor work for? You. That is worth stating because it is not always the case in a…
View Treatment
Executive Health Assessment
Why is blood pressure the most commonly mishandled measurement? Because a single clinic reading in a rushed appointment is exactly…
View Treatment
Annual Executive Medical Review
Why is the second review more informative than the first? Because a single value is a point and two values…
View Treatment
Why Early Treatment Can Matter
Does fixing sleep actually change anything measurable?
Yes, and faster than most people expect. In a randomised trial of 80 adults with overweight who habitually slept under 6.5 hours, a single sleep hygiene counselling session aimed at extending time in bed to 8.5 hours increased sleep by 1.2 hours a night.
Over two weeks that group reduced energy intake by 270 kcal a day and lost 0.87 kg compared with controls. Nobody dieted.
In a pilot study of students, extending sleep by an average of 43 minutes reduced systolic blood pressure and improved glucose control after meals.
What is at stake if it does not change?
The list of outcomes associated with insufficient sleep is long and includes accidents and workplace errors, cardiovascular disease, diabetes, obesity, cognitive impairment, immune dysfunction and mental health problems.
The workplace errors and the driving risk are the ones with the shortest fuse.
What actually works
- A fixed bedtime and wake time, including weekends
- Dim light two to three hours before bed, and no screens for at least the last 30 minutes
- No caffeine within about nine hours of bedtime
- Daily exercise, timed to morning or early afternoon rather than late evening
- A cool, dark, quiet bedroom
- Morning bright light, which stabilises the rhythm and reduces daytime sleepiness
- Naps of about 20 minutes if needed. Over 30 minutes produces grogginess on waking
When is more than advice needed?
When sleep remains inadequate despite all of the above, or when the problem is insomnia rather than insufficient opportunity. Cognitive behavioural therapy for insomnia is the specific treatment, and it works.
Why Early Treatment Can Matter
Does fixing sleep actually change anything measurable?
Yes, and faster than most people expect. In a randomised trial of 80 adults with overweight who habitually slept under 6.5 hours, a single sleep hygiene counselling session aimed at extending time in bed to 8.5 hours increased sleep by 1.2 hours a night.
Over two weeks that group reduced energy intake by 270 kcal a day and lost 0.87 kg compared with controls. Nobody dieted.
In a pilot study of students, extending sleep by an average of 43 minutes reduced systolic blood pressure and improved glucose control after meals.
What is at stake if it does not change?
The list of outcomes associated with insufficient sleep is long and includes accidents and workplace errors, cardiovascular disease, diabetes, obesity, cognitive impairment, immune dysfunction and mental health problems.
The workplace errors and the driving risk are the ones with the shortest fuse.
What actually works
- A fixed bedtime and wake time, including weekends
- Dim light two to three hours before bed, and no screens for at least the last 30 minutes
- No caffeine within about nine hours of bedtime
- Daily exercise, timed to morning or early afternoon rather than late evening
- A cool, dark, quiet bedroom
- Morning bright light, which stabilises the rhythm and reduces daytime sleepiness
- Naps of about 20 minutes if needed. Over 30 minutes produces grogginess on waking
When is more than advice needed?
When sleep remains inadequate despite all of the above, or when the problem is insomnia rather than insufficient opportunity. Cognitive behavioural therapy for insomnia is the specific treatment, and it works.
Measurable within two weeks
Extending sleep by 1.2 hours a night reduced energy intake by 270 kcal daily and weight by 0.87 kg in a randomised trial, with no diet involved.
What insufficient sleep is linked to
Accidents and workplace errors, cardiovascular disease, diabetes, obesity, cognitive impairment and mental health problems.
Countable changes
Hours of sleep, caffeine cut off time, units of alcohol, minutes of activity and blood pressure. All of them have numbers.
Cost & Consultation Investment
The consultation is quoted individually and any tests are quoted before they are ordered. A sleep diary costs nothing and gives more than most tests would. Where the picture points to obstructive sleep apnoea or another sleep disorder, a sleep study or specialist referral is discussed and quoted before it is arranged rather than assumed.
Frequently Asked Questions
It is, but it is rare. A genuine short sleeper gets under six hours with no daytime symptoms at all. Fatigue, irritability or reliance on caffeine means you are not one.
It helps in the short term, but a large weekend to weekday gap is itself the clearest sign of chronic weekday sleep debt. The fix is the weekday schedule, not the weekend.
About 8.8 hours before bedtime, based on a meta analysis. On average caffeine adds nine minutes to falling asleep, twelve minutes of night waking, and removes about 45 minutes of total sleep.
It shortens the time to fall asleep and then makes the second half of the night worse, with more waking, more light sleep and lower sleep quality.
Reasonably for total sleep time, less so for the rest, and they work best in people without a sleep problem. They are useful alongside a clinical assessment rather than instead of one.
About 20 minutes helps daytime fatigue and even cognition. Over 30 minutes tends to produce grogginess on waking. Avoid late afternoon naps if you have trouble sleeping at night.
That points away from short sleep and toward a sleep disorder such as obstructive sleep apnoea or restless legs, or a medical cause. Those need their own investigation and do not improve with going to bed earlier.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
- Cardiovascular diseases
- Cardiovascular disease: risk assessment and reduction
- Hypertension in adults: diagnosis and management
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.