Doctors on both sides of the border now say a short nap can curb irritability, sharpen memory and, most importantly, make people more productive.
"The power nap is more sexy, more snappy," said Dr. Jose S. Laredo, who was born in the Mexican state of San Luis Potosi and now heads the Sleep Medicine Center at University of California San Diego. "The purpose is different. It's not just to have leisure time, it's to recover yourself so you can keep on working. That's why it's looked at in our society, which is go-go-go, as better."
The stereotype of the lazy Mexican catching a few Z's in a hammock is rapidly fading. Today's napper is a business executive tilted back in a leather chair taking a 30-minute break to fight off that afternoon grogginess known as the "midday dip" before resuming a hectic schedule.
History is full of nap-takers. John F. Kennedy, Albert Einstein, Winston Churchill, Napoleon Bonaparte, and Leonardo de Vinci all grabbed a few winks during the day. Even President George W. Bush has been known to take a fast nap, according to the Washington, D.C.-based National Sleep Foundation.
Sleepiness naturally sets in every day between 3 p.m. and 5 p.m. Unless the person suffers from chronic insomnia, doctors say a nap is just the prescription.
Consider a study done by Dr. Mark Rosekind with commercial airline pilots making nine-hour flights to Japan. After taking a 26-minute nap in the cockpit as two other pilots flew the plane, each of the pilots experienced a 34 percent boost in performance. They also reported a 54 percent boost in alertness.
"When you think about it culturally, the folks who take siestas got it right," said Rosekind, president and chief scientist at Alertness Solutions in Cupertino, Calif., and former director of the Fatigue Countermeasures Program at the NASA Ames Research Center. "They were listening to their bodies and said, 'Let's go take a nap and come back and get the job done.' In the United States, we have it totally backward. Three to five? We just keep pushing."
"People are more rested, they're more alert, they're more productive, so that means they're working safer," said Dr. Dennis Holland, who directs the company's alertness management program. "That benefits us and the employees."
Companies have discovered that "a rested brain is a more creative brain," he said.
Some firms have "relaxation rooms" with day beds or tents equipped with sleeping bags, eyeshades and an alarm clock to keep workers from oversleeping. Others have even participated in National Napping Day, an annual event held the day after daylight saving time begins.
But just as the power nap is catching on in the U.S., Mexicans seem to be abandoning siestas. Their days are so crowded with urban pressures - bosses with urgent deadlines, traffic, kids who need to be driven home from school - that they can't afford the quick pick-me-up that was once a national ritual.
"Mexicans are losing the tradition of the family lunch followed by a short siesta," said Dr. Alberto Servin, who heads Baja California's only sleep clinic. "In cities like Tijuana, where it takes an hour to get from one end of the city to the other, going home during the day is impractical."
Servin squeezes a power nap into his schedule during the break between his daytime practice at a government hospital and his evening practice at his Tijuana clinic.
When Servin wakes up, "I feel like new," he said.
Siestas aren't uniquely Mexican. Scientists estimate that two-thirds of the world's population takes an afternoon nap.
"Any culture where there are very hot afternoons, people will divide their day into a main sleep period of six hours and nap of a couple of hours," said Dr. Gregory Belenky, director of the Sleep and Performance Research Center at Washington State University. The traditional Mexican lunch break from 3 p.m. to 6 p.m. is "right on the mark," Belenky said. "That's a time that's conducive to sleep, when the gauge to sleep is open."
Belenky, whose motto is, "You snooze, you win," said the negative stereotypes about Mexican siestas simply don't fit with new research on napping conducted by sleep specialists.
Some data suggests that "dividing your sleep is actually better than one consolidated sleep," he said. "It's like filling your gas tank. Does it matter if you fill five gallons here and five gallons there, or fill all 10 gallons at once? The effect, in terms of the numbers of miles you can travel, is the same." The problem is that most Americans work too far from home and are trying to cram too many activities into the day to find time for a nap.
"We have a cultural bias against naps," said Rosekind, "you know - if you nap, you're stupid, dumb, lazy."
That negative image forces some weary American workers to seek out unorthodox places to fight off drowsiness. According to one study, the place that Americans most commonly nap during the day is in a bathroom stall, with a roll of toilet paper as a pillow.
It was only a decade ago that doctors began linking lack of sleep to serious health problems.
When Dr. Reyes Haro opened his sleep clinic in Mexico City in 1998, his own colleagues were skeptical.
After all, who would think snoring was a sign of anything but deep, healthy sleep? Who would believe that insomnia, or waking up several times a night, could actually make you sick?
"People went to witch doctors. They drank herbal teas. They took their neighbor's advice. We were their last resort," said Haro, who heads the National Autonomous University of Mexico's Clinic for Sleep Disorders and has treated more than 40,000 patients. Mexico isn't the only place where people have been slow to accept the scientific findings on sleep disorders.
It was only last year that the American Board of Medical Specialties recognized sleep medicine as a specialty. And an estimated 85 percent of Americans who have sleep disorders still are not being treated.
Laredo suspects the sleeping habits of Mexicans deteriorate when they go to the United States. He is conducting a study comparing the patterns of 2,000 Caucasians and 2,000 Mexican-Americans in the United States.
"When people come here, they adopt the bad habits of the U.S., not the good ones. They don't start jogging and eating vegetables. They go for the meat and they go for the television. There's more insomnia here, most likely, more obesity. It is a more stressful life."
When Laredo visits his family's cattle ranch in San Luis Potosi, he joins his father in taking an afternoon siesta.
"He works hard and after lunch, everybody takes a little nap," Laredo said with a laugh. "You're out there in the field under a tree. It actually feels good."
Juan Lopez, a 54-year-old communications executive being treated at Haro's clinic, said he sleeps five to 10 minutes every day after finishing lunch at about 5 p.m.
When he leans back in an easy chair in his Mexico City office, it takes him back to his childhood in the northern border state of Sonora. As the desert heat rises, most businesses there still close for the siesta.
"It is part of the regional culture," he said.
Dr. Sonia Meza, director of the federal government's sleep disorder clinic in Mexico City, said Mexicans are losing a healthy tradition.
"The problem is we are sleeping two hours less than we did 100 years ago," said Meza, "because we watch the television until very late, because in these huge cities we have to get up very early to go from one place to another, because in the workplace you are not perceived as competitive if you say, 'Excuse me, I'm going to sleep.' "
