ISLAMABAD: Do you sleep between seven to nine hours per night? According to the experts, this is the amount needed, on average, to keep our minds alert and our bodies healthy — but many people aren’t getting enough.

In the United States, for example, half the population sleeps less than seven hours during the week, according to the 2013 International Bedroom Poll. To make amends, many of us resort to catching up when circumstances allow, whether it’s sleeping in on weekends or napping during the day.

But this catch-up can have its own impact on your body, and when the catch-up becomes too much, it could even be a sign of an underlying health problem.

The much-loved weekend snooze stems from the need to catch up on sleep lost during the week.

“That’s an attempt to pay back sleep deprivation,” says Charles Czeisler, chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston.

But Czeisler is not an advocate of sleeping late over the weekend. He calls it “sleep bingeing” and says it’s a break from consistency that leads to further disruption of our sleep cycles.

Sleep takes place in cycles of rapid eye movement (REM) sleep and slow-wave sleep (non-REM sleep) that alternate in approximately 90-minute cycles.

The extra hours of sleep, but more important the later time of awakening, on weekends leads to confusion and displacement in the body when people return to their weekday routine — something Czeisler defines as “social jet lag.”

“If you’re getting up at 6 a.m. and then noon, that’s the equivalent of Boston to Paris” in time zones, he says.

Making a habit of this is not a healthy lifestyle to lead, according to Czeisler. “It’s a form of sleep bulimia with this chronic bingeing,” he says. Such cycles disrupt sleep integrity, meaning people miss vital moments in their sleep cycle, such as REM cycles.

Even worse, in Czeisler’s view, is the “crash and burn” cycle many live by, in which they skimp on sleep and drive themselves to the point of exhaustion and then crash.

This “has adverse health consequences. … It’s better to have consistency of sleep,” he said.

The daytime nap can do wonders to improve alertness, performance and overall mood — and for many, it offers a moment of relaxation.

Naps of only 20 to 30 minutes are recommended by the U.S. National Sleep Foundation, to avoid grogginess and disruption of night sleep.

“It would be better not to get sleep-deprived in the first place,” Czeisler said. “However, once you are there, it is important to get as much sleep as possible as quickly as possible. That is where naps can help a lot.”

But the desire to nap every day, despite having had a good night’s sleep, could be a sign of something more serious, particularly in countries where siestas are not the norm.

“Habitual daytime naps are more likely to be indicative of sleep deficiency, chronic … disruption or a disorder such as obstructive sleep apnea, depression or cancer,” Czeisler said.

Professor Francesco Cappuccio and his team at the University of Warwick in the UK, have explored what daily napping says about our health. The team studied the daytime napping habits of more than 16,000 men and women in the UK and found daily napping — of both less than and more than one hour — to be a warning sign of an underlying health risk, particularly respiratory problems.

“(Regular) napping is associated with increased risk of disease,” Cappuccio said. As a result, keeping an eye on daily napping habits could help spot upcoming health conditions.

Mediterranean-style “siestas” were not included in the study, as they were classed as a “pattern of life” associated with hot climates. “In Northern European countries, it’s usually a forced nap. You’ve been pushed to have a nap,” Cappuccio said.

The reasons behind this increased risk still need to be explored.

“(This) does not prove that napping is dangerous,” Czeisler noted. He instead says that if someone spends eight or nine hours per night in bed but is exhausted every afternoon, they should be evaluated for a sleep or medical disorder.

When a person is sleeping less than six hours per night, the missing hours accumulate over time. The reasons for such deprivation are wide-ranging, including jet lag, caring for children, working late and early rising — but once paid back, the need to sleep excessively should be gone. Cue the vacation sleep-fest.

“You can’t pay it all back at once,” Czeisler said of the need to slowly pay back sleep loss accumulated over time.