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Listening at home⏱️ Estimated reading time: 13 min
On this page: Overview
Key Takeaways
How does light affect sleep? Light at night tells your body clock it is still daytime. In the evening it delays melatonin, the hormone that prepares you for sleep, and during the night it can suppress it, so you fall asleep later and the night’s darkness signal weakens. Noise works differently, mostly by waking you briefly.
Most people only notice bedroom light when something changes. One Sheffield homeowner described a new LED street lamp about eight metres from his bedroom window, bright enough that blackout blinds and curtains didn’t stop it. Others tape the top and sides of their curtains and still see light creeping in at the edges.
At Bollsen we make earplugs and sleep products trusted by 1,000,000+ people, and we hear about bedroom light almost as often as bedroom noise. Every source has a simple answer, and a sleep mask is the last step, not the first.
How does light affect sleep?
Light affects sleep mainly through the circadian rhythm, your roughly 24-hour body clock, because light reaching the eyes in the evening or at night reads as daytime and delays and suppresses melatonin, the hormone the pineal gland releases in darkness to get the body ready for sleep.
The clock sits in the suprachiasmatic nucleus of the brain. Morning light sets it forward, late-evening light pushes it back.
The clearest numbers come from a 2011 study in the Journal of Clinical Endocrinology and Metabolism of 116 adults aged 18 to 30. Compared with dim light under 3 lux, ordinary room light under 200 lux in the eight hours before bed delayed the start of melatonin release in 99% of participants. It also shortened the time melatonin was present by about 90 minutes.
The same researchers kept the room light on during the usual hours of sleep, and melatonin was suppressed by more than 50% in most trials. Light before bed mostly moves sleep later. Light during the night works against the darkness signal while you are trying to stay asleep.
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Life+★ 4.7 · 3,700 reviewsLife+★ 4.7 · 3,700 reviewsMusic SoundPRO★ 4.8 · 514 reviewsWatersafe+★ 4.8 · 684 reviewsLife+★ 4.7 · 3,700 reviewsWhich bedroom lights disturb sleep the most?
In a typical UK bedroom the light sources that matter most are, roughly in order, a street lamp through a curtain gap, a partner’s reading lamp, phone and TV screens, standby LEDs and the early sunrise of May to July, ranked by how bright they are at pillow height and how much of the night they last.
Street lamps come first because they stay on all night, and many councils now use LED lanterns with a whiter light than the old orange sodium lamps. The light rarely comes through the curtain fabric. It comes round the edges.
A partner reading in bed puts a lamp about a metre from your face, right in the evening window when room light delays melatonin. Screens sit close to the face, give off blue-rich light and often stay on until lights-out.
Standby LEDs are the dimmest source on the list, but they glow all night. Then there is dawn. Under British Summer Time the sun rises before 5am across much of the UK in June, around 4:40am in London and a little earlier in Edinburgh, and the seasonal side of waking up at 5am in summer has its own guide.
Curtains that seem fine in December let that light straight in. One sleeper admitted draping a dark T-shirt over their head for the last hour of summer nights.
| Light source | Why it matters for sleep | Simplest change |
|---|---|---|
| Street lamp through a curtain gap | On all night; LED lanterns give a whiter light; leaks round the curtain edges | Overlap and seal the curtain edges, ask the council about a shield, wear a mask |
| Partner’s reading lamp | Bright and close during the evening window when light delays melatonin | A warm, dimmable bulb aimed away from your side, or a mask while they read |
| Phone, tablet and TV screens | Close to the eyes, blue-rich, used right up to lights-out | Screens off an hour before bed, phone face down |
| Standby LEDs | Dim, but on all night; blue or white ones near the pillow count most | Black tape or dimming stickers, or turn the device to the wall |
| Early sunrise (May to July) | Sun up before 5am in June under BST, often before your alarm | Blackout lining or blind, then a mask for what still gets through |
Does a small LED really matter?
A single dim standby LED across the room is unlikely to matter much, but a bright blue or white one at pillow height, or several together, is worth covering, because Harvard Health reports that dim light of about 8 lux can already affect the body clock and melatonin.
Eight lux is very little. Harvard describes it as a level most table lamps exceed and about twice the output of a night light. We have not found a study that measures standby LEDs directly, so take this as practical advice rather than a research finding.
Distance and colour count most. An LED a metre from your face puts far more light at your eyes than one on the far wall, and blue or white indicators come first. Black tape, dimming stickers or turning the charger to the wall will do.
Is blue light worse for sleep than warm light?
Blue light at night is more disruptive than warmer light. In research summarised by Harvard Health, 6.5 hours of blue light suppressed melatonin for about twice as long as green light of similar brightness and shifted circadian rhythms by 3 hours, against 1.5 hours for green.
Harvard also notes that dim red light is less likely to shift the body clock or suppress melatonin. So a dim red or amber night light suits a bedroom better than a bright white one.
On screens, the advice differs mostly in how cautious it is. NHS Every Mind Matters sleep advice suggests no phones, tablets or computers for an hour before bed, saying the blue light from screens can make it harder to fall asleep. Harvard goes further and suggests avoiding bright screens for two to three hours before bed.
Can light reach you through closed eyes?
Yes. Closed eyelids dim light but do not stop it, and the Sleep Foundation’s guide to light and sleep says plainly that closing your eyes isn’t enough, because eyelids can’t block sufficient light and circadian effects can occur at low indoor light levels even with the eyes shut.
Close your eyes and face a sunny window, and the reddish glow you see is light passing through the lids. Direct sunlight reaches up to 10,000 lux against about 500 lux for bright office lighting, the Sleep Foundation notes. A street lamp is far dimmer, but the principle holds.
How much a mask lets through is a separate question about fit, covered in why some sleep masks still let light in. For the bedroom, shut eyes are no substitute for a dark room.
How do noise and light affect your ability to stay asleep?
Light and noise disturb sleep in different ways. Light acts mainly on the body clock, delaying and suppressing melatonin so sleep starts later and the darkness signal weakens through the night, while noise mostly breaks sleep up by waking you briefly. A settled night needs a room that is both dark and quiet.
The sound half lives in our sleeping guides. Our article on how noise affects sleep sets out the levels at which night-time sound starts to matter, and the overlap between the two through the body clock is explained in noise and your circadian rhythm, alongside the research on sound at night.
On the practical side, passive earplugs are the simplest step for quiet, and our guide to earplugs for sleeping covers fit, comfort and side sleeping. If you want darkness and quiet in one set, our Deep Sleep Duo pairs the Deep Sleep Mask with Life+ earplugs, rated SNR 24 dB.
What is the easiest way to make a bedroom darker?
The easiest way to make a bedroom darker is to start with the cheapest changes and work upwards, covering standby LEDs, turning the phone face down and sealing the curtains before you buy anything, then adding warmer bulbs for the evening and a sleep mask for whatever light the room still lets in.
Cover the small lights first
Tape or dimming stickers on chargers, routers and the TV take a minute. The NHS also suggests keeping clocks out of view and turning your phone face down.
Warm the bulbs for the evening
Use a warm-white, dimmable bedside bulb and keep the ceiling light off for the last hour. For night-time bathroom trips, a dim red or amber night light beats the big light.
Close and seal the curtains
Light comes round curtains more than through them. Overlap them in the middle, hang them close to the wall, and add a blackout lining or a fitted blind if the top edge glows. We weigh the two approaches in sleep mask vs blackout curtains.
Ask about the street lamp
If a street lamp shines straight into a bedroom window, contact your local council. Councils can sometimes fit a shield to the lantern, which is what the Sheffield homeowner asked for, and asking costs nothing.
Add a mask for the light you can’t remove
Some light stays whatever you do. Dawn in June is one, a partner’s lamp another, and a hotel room is anyone’s guess. NHS advice lists wearing an eye mask if light is still a problem, and a mask goes wherever you sleep.
For that last layer of darkness our own choice is the Deep Sleep Mask, a mulberry silk sleep mask designed for total darkness, with an adjustable Velcro strap that won’t pull your hair; it folds flat for travel and washes at 30 °C. What the research says about masks in general is covered in do sleep masks work.
When should you speak to a GP about sleep?
If the bedroom is dark and quiet and poor sleep still carries on for weeks, or starts to affect your days, speak to a GP. The NHS guidance on insomnia explains what counts as insomnia and what a GP can help with.
A darker bedroom supports the body’s natural melatonin release in darkness. It is a good sleep habit, not a medical answer.
Light reaches your body clock long before it bothers your eyes, and even a small blue-white glow near the pillow can count. Start with what’s free tonight. Tape over the LEDs, put the phone face down and seal the curtain edges, then keep a mask for the light you can’t switch off.
His connection to hearing protection stems from personal experience with sound sensitivity during live events and work in noisy environments, an issue that made him more aware of the long-term risks of unmanaged noise exposure. Today, as both a communicator and a user of BOLLSEN products, he is passionate about raising awareness around the importance of proactive hearing care.
At BOLLSEN, he develops data-driven marketing campaigns, writes SEO-focused articles, and manages communication channels that connect customers with practical knowledge about hearing protection. His work ensures that BOLLSEN’s message—prioritizing health, performance, and sustainability reaches a global audience in an engaging and trustworthy way.
Passionate about writing since childhood, Timotej combines creativity with a strong analytical approach, continuously testing new ideas in digital marketing, performance advertising, and social media. He believes in learning through innovation and collaboration, balancing leadership with openness to new perspectives.
Beyond his professional role, Timotej is committed to a healthy lifestyle and finds inspiration in fitness, sports, and quality time with friends. His personal passion for well-being aligns with BOLLSEN’s core values, making his work not only a career but also a cause he deeply believes in.
