In Muslim-majority Oman, most people wake before dawn for morning prayers. People often go back to sleep afterward or take afternoon naps, says sleep medicine researcher Mohammed Al-Abri of Sultan Qaboos University in Muscat, Oman.
Such segmented sleep is not limited to Muslim countries. Teenagers, new parents, perimenopausal and menopausal women and elderly individuals everywhere can struggle to sleep the recommended seven to nine hours in a single block. Early school and work start times leave night owls without adequate sleep. Shift workers juggle daytime demands with nighttime working hours, cramming in sleep when they can. And people living in some of the world’s hottest regions avoid the midday heat with siestas.
Despite how commonplace various kinds of naps are, scientists have largely focused on monophasic, or single, blocks of shut-eye, researchers report in an Aug. 25 review in Brain Medicine. Yet how people sleep matters as much as how much. That means sleep experts need to pay more attention to patterns in which people combine a core nighttime sleep with one or more naps throughout a 24-hour day.
That requires first thinking about naps beyond the binary of something that people either do or don’t do, another team notes in August in Sleep Health. After all, naps vary in duration, timing, frequency and societal significance. And treating all naps as the same, as is common, has led to wildly divergent findings, with some researchers concluding that naps harm health and others finding the opposite.
Lost in the noise is how to advise the fatigued masses. In theory, splitting up sleep could help people clock in enough snooze-time hours, says occupational health worker Line Victoria Moen, who was not involved with either study. But how that sort of strategic, broken sleep impacts long-term health and well-being remains an open question. “The evidence is too fragmented,” says Moen, of the National Institute of Occupational Health in Oslo, Norway.
A history of ‘two sleeps’
Across the ages, sleep has shown surprising variability, records show. One striking example is medieval Europeans’ two-sleep pattern, described in historian A. Roger Ekirch’s 2006 book At Day’s Close: Night in Times Past. People typically went to bed when the sun went down and then woke in the middle of the night to meditate, complete light chores or have sex, suggests Ekirch, of Virginia Tech in Blacksburg. Then they’d fall asleep again until sunrise.
A sleep intermission no longer jibes with a modern world bathed in electric lights and screens that keep people awake until well past sundown. But could such a biphasic sleep pattern be rejiggered to serve modern populations?
As it stands, people across the industrialized world are chronically sleep-deprived. Not sleeping enough has been linked with numerous mental and physical health woes, including struggles with memory and alertness, weakened performance, heart problems and obesity.
Experts generally advise people to practice better sleep hygiene, such as dimming lights and getting off screens several hours before bedtime. Yet such one-size-fits-all advice overlooks modern realities.
Consider those who work outside a 9 a.m. to 5 p.m. day. Shift workers, who comprise roughly a fifth of industrialized countries’ populations, could try to meet their sleep needs with a single daytime block. But being out of sync with the sun means their sleep will probably be lighter, more fragmented and less restorative than had they slept through the night, sleep researchers João Sena Ribeiros, of the Autonomous University of Barcelona in Spain, and Càtia Reis of the University of Lisbon in Portugal, wrote in October 2025 in Sleep Medicine.
Might such individuals be better off sleeping in blocks before and after their shifts? Science provides no clear answers.
No consensus on long naps
Human biology lends some support for a daytime nap.
Two processes govern when and how we sleep. Sleep pressure builds up the longer we stay awake. And circadian rhythms, governed by natural and artificial light, cue the body to release hormones — melatonin in dim light and cortisol upon waking. Roughly after lunch, shorter “ultradian” rhythms, triggered by sleep pressure buildup and changes to body temperature and blood sugar levels, can trigger a crash.
Honoring that malaise with a power nap of less than half an hour has been linked with increased alertness and cognitive performance. But beware. Shorter naps scattered throughout the day seem to harm mental and physical health, researchers reported in June 2021 in Sleep Health.
But what about a two-sleep pattern better suited to the sleep-deprived modern era, in which people go to bed late and wake up early for school and work? Could such individuals benefit from a big block of nighttime sleep coupled with a long afternoon nap? On this point, the science is murky.
Afternoon naps longer than an hour are linked to a higher likelihood of obesity and elevated blood sugar levels, a risk factor for developing 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 says.
But research on an altogether different population — elite soccer players in Australia — suggests that a long afternoon slumber could help counteract sleep deprivation from early morning practices and late evening games. Researchers brought 12 male soccer players into the lab and connected them to electrodes to measure how long it took them to fall asleep and to monitor sleep stages and sleep quality during either one- or two-hour midafternoon naps.
Though well-rested, the athletes conked out in less than 10 minutes, the team reported in September in Clocks & Sleep. Strategically varying nap length could help with different aspects of performance, the team suspects. That’s because nap length altered the athletes’ sleep patterns.
Sleep cycles are roughly 90 minutes long and involve two stages: light REM sleep, often marked by dreaming, and non-REM sleep, which includes deep sleep. Research suggests REM sleep is linked with improved learning and memory, and deep sleep is linked with recovery from exercise. Athletes who napped for one hour spent a larger fraction of time in deep sleep compared with athletes who slept two hours, who had longer REM sleep. That hints at the possibility that shorter naps could facilitate recovery, while longer naps facilitate new skills, the team notes.
That and other research is starting to show that under the right conditions, long naps may be beneficial, says Anastasi Kosmadopoulos, a sleep researcher at CQUniversity Australia in Adelaide. “Sleeping in two blocks versus one is not detrimental to overall daily alertness or waking performance.”
Sleep advice should be personal
Another question is whether findings in elite athletes apply to the rest of us. Moving forward, sleep advice needs to be personalized to the individual, Sena Ribeiros and Reis say.
Such personalization should include a genetic analysis, researchers reported in January 2025 in Obesity. Propensity for napping is highly heritable, the team reported in earlier work. In this study of more than 1,200 Spanish participants, the team quantified a person’s genetic predisposition for napping using more than a million genetic variants. Individuals who went against their genetic predisposition, by napping when they ought not to or vice versa, showed increased risk of obesity, while those who followed their genetic predisposition did not.
In their August review in Sleep Health, members of that same team outlined eight core features of naps that researchers ought to measure. Besides genetic predisposition and nap frequency, duration and timing, researchers should also consider an individual’s motivation for napping, cultural and home environments, seasonality and sleep status.
Experts don’t need to prove that two sleeps are better than one, Sena Ribeiros says. They just need to address how individuals who cannot get their sleep in a single, nighttime block can get as close as possible to meeting their sleep needs. “We should look at [sleep] in a more personalized way instead of … just saying, ‘OK, try to get those seven hours’ to everyone,” he says.
