Your sleep starts when you wake up
Most people treat sleep like a nighttime problem. They tweak pillows, buy supplements, and scroll through endless tips at 11 pm.
But a lot of sleep quality is decided earlier in the day, by signals that set your body clock and dial up or down your evening sleep pressure.
Four of the most reliable levers are light after waking, caffeine timing, meal timing, and evening light. You might already track them. The harder part is knowing the right dose for you.
Here is the science, plus a simple way to personalise it without turning your life into a lab.
1. Morning light is a timing signal, not a wellness trend
Your brain uses light as its strongest cue for when daytime begins. Morning daylight helps align your circadian rhythm, which influences alertness in the day and the timing of sleepiness at night. Morning sun exposure has been linked with better circadian alignment and sleep health in research.
The key detail is that indoor light is usually too dim to provide the same signal. Daylight outdoors is dramatically brighter, even on a cloudy UK morning.
How to find your morning light dose
Start with a small, repeatable baseline and adjust using your sleep outcomes.
Begin with 10 to 20 minutes outside within an hour of waking
If mornings are very dark, extend it, or add a second outdoor break later in the morning
Track two things for a week
time to fall asleep
how often you wake in the night
If you are still not sleepy until late, you often need more morning light and a more consistent wake time. If you are sleepy too early, you may be over shifting your rhythm earlier and should shorten the light window or delay it slightly.
2. Caffeine can disturb sleep even when you feel fine
Caffeine blocks adenosine, one of the main drivers of sleep pressure. That is why it helps you feel alert. It is also why it can quietly reduce sleep depth and total sleep time.
A classic controlled study found that 400 mg caffeine taken even 6 hours before bedtime significantly disrupted sleep. More recent work suggests the effect depends on both dose and timing, with larger amounts having longer reach into the night.
This is why some people can drink coffee after dinner and still fall asleep, yet they wake up unrefreshed. Falling asleep is not the same as getting good sleep.
How to find your caffeine cut off time
Instead of guessing, run a simple two week test.
Week one
keep your usual caffeine amount
stop caffeine 8 hours before bed
Week two
keep the same amount
stop caffeine 6 hours before bed
Compare
how long you sleep
how many awakenings
how you feel mid morning
If week one is noticeably better, your personal cut off is likely closer to 8 hours. If they are similar, 6 hours may be enough. If sleep is still fragile, reduce the dose as well as shifting the timing.
3. Meal timing affects sleep through temperature, digestion, and the body clock
Eating is another timing cue for the body. Late meals can push digestion and metabolism later into the evening, and may increase sleep disruption in some people.
Studies linking meal timing and sleep quality suggest that later eating patterns are associated with poorer sleep outcomes.Experimental and observational research also points to late food intake being associated with impaired sleep quality and changes in sleep structure.
This does not mean everyone must eat early. It means the closer your last meal is to bedtime, the more likely it is to interfere, especially if the meal is large, spicy, or high fat.
How to find your latest stable dinner time
Use a simple rule, then personalise.
Aim to finish your last main meal 3 hours before bed for one week
If you sleep better, keep it
If you already do this and sleep is still variable, test 4 hours for five nights
If you get early morning waking or hunger, try a smaller earlier dinner and a light snack earlier in the evening
Your goal is not perfection. It is stability.
4. Evening light tells your brain it is still daytime
Light in the evening can suppress melatonin and shift the body clock later. This is especially true for bright, blue enriched light, including many screens and LED lighting.
Lab studies have shown that screen and LED light in the evening affects circadian physiology and alertness, consistent with melatonin suppression and phase delay.
This is one reason you can feel wired at night after being on your phone, even if you are physically tired.
How to find your light sensitivity level
Run a three night comparison.
Nights 1 to 3
dim your home lighting 2 hours before bed
keep screens lower brightness and further away
avoid bright overhead lights
Nights 4 to 6
keep everything else the same
return to your usual lighting habits
If your sleep onset, awakenings, or morning grogginess worsens in nights 4 to 6, you are likely more light sensitive and will benefit from a stricter evening light routine.
Putting it together without obsessing
You do not need to control everything. You need the highest leverage inputs to be consistent enough that your body can predict what is coming.
Try this for 10 days
Wake time within a one hour window
Outdoor light most mornings
Caffeine with a clear cut off
Dinner finishing at least 3 hours before bed
Evenings that get dimmer, not brighter
Then look for the pattern. The right dose is the one that produces the most stable sleep, not the one that sounds most impressive.
When to get help
If you have persistent insomnia, loud snoring, choking or gasping at night, or significant daytime sleepiness, it is worth speaking to a doctor. The Wellness offers same day GP appointments, prescriptions, and health programmes where you get 24/7 access to a health concierge, priority bookings, A lead GP overlooking your care and access to the latest health research and treatments.