Danish Study Links Evening Screen Time to Delayed Sleep Onset

A 2025 University of Copenhagen study of 1,200 residents found that participants who reduced phone and tablet use after 9 p.m. fell asleep 14 minutes faster on average than those who kept screens on until bedtime.

The finding arrives as more Copenhageners report fragmented rest amid longer workdays and hybrid schedules that keep laptops open late in living rooms across Østerbro and Nørrebro. City health surveys from last year showed one in three adults in the metro area logs at least three hours of screen time between dinner and midnight, a pattern linked to delayed melatonin release and next-day fatigue.

Local programs are already testing fixes. The City of Copenhagen’s Sund By initiative runs free evening workshops at the Nørrebrohallen sports complex on how to dim device brightness and set app timers, while the Frederiksberg Library hosts monthly talks on light exposure that draw residents from nearby streets like Gammel Kongevej. Both efforts started in spring 2025 and have enrolled more than 800 participants so far.

Numbers behind the advice

Researchers measured wrist-worn light sensors and sleep trackers for two weeks. They recorded a 22 percent rise in sleep latency among those exposed to more than 30 lux of blue light after 10 p.m. The same cohort spent an average of DKK 1,800 last year on melatonin supplements and blackout curtains, according to pharmacy sales data released by the Danish Medicines Agency in March. Participants who followed simple rules-phone chargers outside the bedroom and warm lighting after sunset-cut their supplement spending by roughly 40 percent within six weeks.

City health officials plan to expand the workshops to Amager this autumn and will track whether average sleep duration rises above the current 6.8 hours reported in the 2025 survey. Residents can sign up through the Sund By app or at district libraries; the next session at Nørrebrohallen begins 19 August.