If you only fix one thing about your bedroom, make it darkness. Of all the popular “sleepmaxxing” levers — trackers, supplements, gadgets — blocking light is the one with the most convincing science behind it.
What the research suggests
A 2022 Northwestern University study found that sleeping in even dim light — the kind that leaks from a streetlamp or a standby LED — was associated with a higher nighttime heart rate and poorer glucose regulation the next morning, compared with sleeping in a darker room. The takeaway isn’t alarming; it’s simple: your body reads light as information, and at night, less is better.
This matters because light is one of the few sleep variables you can control completely and cheaply. You can’t always quiet your mind on command. You can make your room dark.
What “dark” actually means
Most people dramatically overestimate how dark their bedroom is. Phone on the nightstand, a sliver under the door, the glow of a charger — it adds up. True darkness is closer to zero lux: hold your hand in front of your face and you shouldn’t really see it.
Two changes get you most of the way there:
- Seal the windows. A portable blackout kit stops the light creeping around blinds and curtains — especially useful for renters, travellers and shift workers.
- Wear a proper mask. A flat $4 satin mask leaks light at the nose and slides off by 2am. A contoured, weighted silk mask seals at the nose and stays put — the difference between “dim” and “gone.”
Why we anchor on darkness
At Dusk & Down we deliberately avoid health claims we can’t stand behind. Darkness is the exception we’re happy to talk about, because the evidence is real and the fix is genuinely within reach. It’s the foundation of a good wind-down — everything else (scent, weight, a screen-free hour) builds on top of it.
Start dark. The rest of the ritual follows. Explore the full ritual →
This article is for general education and isn’t medical advice. If you have a sleep disorder, please speak with a clinician.