Avoid glowing screens one hour before bed; if you must, read paper books or e-ink devices instead

Cost: No cost involved. Giving up phone use one hour before bed requires willpower, especially when fighting long-standing habits.
In plain terms: Reading from glowing screens before bed delays sleep onset by roughly 10 minutes compared to reading paper books. It also lowers melatonin production by 55%. The next day, the body’s internal clock shifts more than 1.5 hours later, making mornings harder and requiring extra time to feel fully awake.
Benefit: In controlled lab experiments, the same participants were tested under both conditions (cross-over design). Those reading from glowing e-readers fell asleep about 10 minutes later than those reading paper books (25.7 minutes versus 15.8 minutes). Their nighttime melatonin levels dropped by 55%, and their circadian rhythm shifted by over 1.5 hours — melatonin secretion started at 22:31 instead of 21:01. This resulted in greater morning sleepiness and a longer recovery time to full alertness.
Evidence grade: B
Sources:Chang, Aeschbach, Duffy & Czeisler (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. https://doi.org/10.1073/pnas.1418490112
Notes: The study involved a small number of participants and was conducted under tightly controlled lab conditions. Real-world effects may be smaller given typical phone brightness and usage patterns. The study did not evaluate how much nighttime screen modes actually help.