Screen Time and Sleep: What the Research Actually Shows

Adults who use a smartphone or tablet for more than two hours in the 90 minutes before bed take, on average, 45 minutes longer to fall asleep than those who don't. That figure, drawn from a 2024 meta-analysis published in Sleep Medicine Reviews, is the kind of number that gets filed away and forgotten — usually while scrolling Instagram at midnight. In Lisbon, a city that already runs late by Northern European standards, the problem has a particular texture.

The timing matters. Lisbon's dinner culture pushes meals toward 9 or 10 p.m. in many households, nightlife in Bairro Alto and Cais do Sodré runs until well past 2 a.m. on weekdays, and the summer light in July doesn't fully fade until nearly 9:30 p.m. Stack a bright screen on top of all that and the body's melatonin production — the hormone that signals the brain to prepare for sleep — gets knocked back by an hour or more, according to research from the Harvard Medical School Division of Sleep Medicine. Poor sleep is not a personal failing. It is, increasingly, an environmental design problem.

What the Science Actually Says

The blue light argument is real but incomplete. Screens emit short-wavelength blue light that suppresses melatonin, yes — but researchers at the University of Manchester published findings in 2023 clarifying that the brightness of the screen is at least as important as its colour temperature. A dim, warm-toned screen used for a relaxing activity causes less disruption than a bright one used for anything cognitively stimulating: news, social media, work email. The content, not just the light, is the problem. Stress arousal keeps the nervous system in a mild fight-or-flight state long after the phone is put down.

Sleep trackers — the Garmin Forerunner series and the Oura Ring Gen 4 have both surged in sales across Portugal in 2025, with the Oura retailing at around €349 in Lisboa stores — have generated millions of data points that broadly confirm the lab findings. Users who logged more than 90 minutes of screen time after 10 p.m. recorded average deep-sleep durations roughly 18 percent shorter than on nights they abstained. The caveat: self-reported data is messy. People who are already anxious about sleep may use their phones more, creating a feedback loop the trackers cannot untangle.

Where Lisbon Is Taking This Seriously

A handful of local organisations have started building sleep literacy into broader wellness programmes. The Centro de Medicina do Sono at Hospital CUF Descobertas, on the eastern waterfront in Parque das Nações, runs a 6-week cognitive behavioural therapy for insomnia programme — CBT-I — that includes a dedicated session on digital hygiene. The programme costs approximately €420 for the full course and has a waiting list running to late September 2026. Meanwhile, the yoga and mindfulness studio Espaço Yoga Lisboa, on Rua da Madalena in the Alfama neighbourhood, introduced a 75-minute "digital detox and sleep" workshop in March 2026 that books out within days of each new date being posted.

Both approaches share a premise: telling people to simply put the phone down does not work without replacing the habit with something else. The CUF programme uses structured wind-down protocols. The Espaço Yoga workshop pairs breathing techniques with a guided body scan. Neither pretends that willpower alone is the mechanism.

The practical picture is not hopeless. Research consistently shows that even a 30-minute reduction in pre-sleep screen time, if sustained for two weeks, produces measurable improvements in sleep onset — the time it takes to fall asleep — and in subjective next-day alertness. Switching a device to its lowest brightness setting and enabling a warm colour filter after 9 p.m. blunts some of the melatonin suppression, though it does not address cognitive arousal from the content itself. A physical book, a podcast, or simply sitting on a Mouraria rooftop watching the city settle down remain stubbornly effective alternatives, at zero cost and zero waiting list.

Anyone experiencing persistent difficulty sleeping should speak with a médico de família or a sleep specialist before drawing conclusions from tracker data alone.