To Nap or Not to Nap? Sleep Science Is Still Waking Up to the Question

Around the world, many people do not sleep in one continuous block: in Muslim-majority Oman, most people wake before dawn for morning prayers and then go back to sleep or take an afternoon nap, says sleep medicine researcher Mohammed Al-Abri of Sultan Qaboos University in Muscat. Teenagers, new parents, shift workers, and people in hot regions who take midday siestas all break their sleep into more than one block too, yet scientists have mostly studied single, uninterrupted sleep, researchers note in an August 25 review in the journal Brain Medicine.

Naps themselves vary enormously in duration, timing, frequency and cultural meaning, another team notes in a separate August review in the journal Sleep Health — and treating all naps as the same has produced contradictory findings, with some studies concluding naps harm health and others finding the opposite. "The evidence is too fragmented," said occupational health researcher Line Victoria Moen of Norway's National Institute of Occupational Health, who was not involved in either study.

Segmented sleep has a long history: historian A. Roger Ekirch of Virginia Tech has documented a "two-sleep" pattern among medieval Europeans in his 2006 book, in which people went to bed at sundown, woke in the middle of the night for an hour or so of activity, then fell asleep again until sunrise. Modern shift workers, who make up roughly a fifth of industrialized countries' populations, face a related challenge: sleep researchers João Sena Ribeiros of the Autonomous University of Barcelona and Càtia Reis of the University of Lisbon wrote in October 2025 in the journal Sleep Medicine that sleep out of sync with the sun tends to be lighter, more fragmented and less restorative.

Human biology offers some support for daytime naps: sleep pressure builds the longer a person stays awake, while shorter "ultradian" rhythms after lunch, driven partly by shifts in body temperature and blood sugar, can trigger an afternoon slump. A nap under half an hour has been linked to increased alertness and better cognitive performance, but afternoon naps longer than an hour have been linked to a higher likelihood of obesity and elevated blood sugar, a risk factor for type 2 diabetes, Al-Abri and colleagues reported in October 2022 in Frontiers in Psychology. "I usually urge people, if they have a nap, to have it less than half an hour," Al-Abri said.