Everydayhealth.com says for many people, a late-afternoon snooze can be beneficial,

Steven M. Scharf, MD, a professor of medicine at the University of Maryland Medical School in Baltimore, explains that the body operates on a 24-hour clock regulating sleepiness and wakefulness. the hardest times to say awake are between 3 and 5 a.m. The second dip for most healthy adults comes in the late afternoon, from approximately 3 p.m. to 6 p.m. Between those hours, a short nap is perfectly healthy, Scharf said.

How Long Can I Nap?

Scharf recommends naps last no more than 30 to 45 minutes. Any longer, and the nap can have a negative effect, interfering with sleep that night. And anyone who needs to nap outside those afternoon hours, like at 11 a.m., probably has other health issues, he added.

Even just 10 minutes of shut-eye in the mid-afternoon can be beneficial, according to a 2006 study in the journal Sleep. The study authors found that a 10-minute nap increased alertness and performance immediately after the nap and lasting up to three hours.

A 10-minute nap may work even better for some people than a 30-minute one, the researchers found, because after a 30-minute nap, there can be a period of grogginess or disorientation — known as sleep inertia — that can last a half-hour or so.

Scharf said there's a tremendous biological variability in people's need for sleep. One person may not need a nap at all, while another might do great after 15 minutes, and someone else may find it hard to get through the evening without a 45-minute nap.

What if you can't nap?

Not everyone who needs a nap can get one, and lifestyle plays a big role in that, Scharf said. In some cultures, napping is a regular (and healthy) part of everyone's day. There's the afternoon siesta in Mexico, and people in Mediterranean countries traditionally close shops and offices in the afternoon hours for a large meal and nap, reopening at 4 or 5 p.m.

But in the United States, people are becoming more and more sleep deprived, possibly because of the demands of increasingly busy days, according to the National Sleep Foundation.

Scharf said he has prescribed 15-minute naps periodically during the workday in extreme cases, such as for some patients with narcolepsy or other sleep disorders, and has found employers by and large to be accommodating.

For people who would benefit from a nap but can't get one, Scharf said that staying active can counteract sleepiness. Caffeine can help as well, he says, but not after 2 p.m., because it can stay in the body for 12 hours — which can lead to trouble sleeping at night, followed by more daytime sleepiness, and on and on.

Another option is for people to strive for an extra half-hour or so of sleep at night. Or, if you get home early enough there's nothing wrong with dropping off," he said.