Why sleep needs change with age
Newborns spend most of the day asleep because sleep drives brain development and growth. Through childhood and the teen years the need gradually decreases, but teens still need 8–10 hours, and their body clocks naturally shift later, which is why early school starts hit them so hard.
For adults, 7–9 hours is the evidence-backed range. Older adults often sleep a bit less (7–8 hours) and experience shorter sleep cycles, around 82 minutes instead of 90, plus lighter, more fragmented sleep. That's normal, but consistently poor sleep is not a normal part of aging and is worth discussing with a doctor.
Quality beats quantity
Hitting the recommended hours matters less if your sleep is fragmented or mistimed. Wake at the end of a sleep cycle using our sleep calculator, keep a consistent schedule, and track whether you're falling behind with the sleep debt tracker.