Less than half of American small business owners will take a vacation this summer, down from 67 percent in 2006, according to a recent American Express survey.

Why so few?

Many cited their busy work schedules (37 percent) while others claimed that they simply couldn't afford it (29 percent). Sixteen percent said that they just don't vacation at all.

But recent research suggests that vacation is more important than you may think—both for the health of the entrepreneur, as well as the health of the business.

The Framingham Heart Study, for example, monitored women's health over the course of 20 years. The research revealed that women who took only one vacation every six years were nearly eight times more likely to develop coronary heart disease. Another study reported by The New York Times in 2008 found that men who did not take a vacation at least once a year had a "21 percent higher risk of death from all causes and were 32 percent more likely to die of a heart attack".

It's always tough to prove causality in studies like these. (Are people who don't take vacations also more likely to eat poorly?) But some entrepreneurs are not taking any chances.

"My wife would kill me if I didn't take some family time this summer to spend with her and our three-year-old and three-month-old," says Matthew Corrin, the 29-year-old founder of Freshii, a fresh food franchise headquarted in Chicago.

Corrin will spend 10 days at his summer cottage and then a week on the beach in Los Angeles, despite his busy schedule that includes opening 20 new locations by September 1.

Katie Shea, co-founder of CitySlips, a New York start-up that sells foldable ballet flats that fit in a purse, says although she hasn't had a break in two years, she plans to take a trip this summer. Both Shea and her partner, Susie Levitt, are also supportive of what they call "mini-vacations," even if for only a day, because of the critical distance from day-to-day work needed to reconsider strategy and innovate.

"It's hard to be creative sitting in an office all day," Shea says. "Once you get out, that's when the ideas start flowing."

Scientifically speaking, she's right. Ever wonder why "a-ha" moments come while resting on the beach or lounging in the bath?

Jonah Lehrer, a writer for Wired, explains. "You have to understand what's happening in the brain when you have an a-ha moment," he says. Lehrer describes how researchers at Drexel College set out to study what happens in a person's brain when he or she experiences some sort of personal discovery. The scientists found that when individuals completed a word puzzle, right before a moment of insight, a cluster of cells located in the superior temporal gyrus—in the right hemisphere of the brain—show significant activity. And accompanying this are also alpha waves, which are closely linked with mental relaxation.

"So why are alpha waves closely predictive of these moments of insight?" says Lehrer. "What these scientists argue is that when you're really focused on the outside world [or on your business] that's where your consciousness is. But when we're a little bored and a lot relaxed, we turn the spotlight of attention inward, and that makes us much more likely to hear this obscure circuit of cells," which makes it possible to get the insight in the first place.

So, while many people assume that finding the answer to a specific problem requires a lot of focus, or just a lot of caffeine, that's simply not the case. 

"That's probably the worst thing you could do," says Lehrer.  "Instead, what we should do is take a hot shower or play ping pong." Or, possibly—take a short vacation. 

And, if you still need a reason to justify your week playing tennis at the shore, consider the following: When you take a vacation, your employees will be happy.

"If you ever worked for someone else, you know how it is when the boss is away. There's a feeling of freedom, of lightness, of relief," says Melissa Chang, the president of Pure Incubation, a digital publishing company in Topsfield, Mass.

"As the boss, you may not want your employees to feel this freedom. But it's important not only for you to get a break, but for your employees to get a break from you. When you get back from vacation, you'll find that they are refreshed, as well."