"Vacations are not a luxury, they're a necessity," John de Graaf, executive director of Take Back Your Time, a non-profit organization that studies issues related to work.
"Men who take them are 32 percent less likely to suffer from heart disease than those who don't," he said. "For women, it's 50 percent. And women who don't take vacations are more than twice as likely to suffer from depression. Pass them by at your peril."
Another study, conducted last July, by LastMinuteTravel.com, indicates 45 percent of 153 million working Americans did not use vacation days in 2009, with 78 percent anticipating they will leave as many as 10 vacation days unused in 2010.
Fifty-one percent say coordinating with family and friends is too difficult, 40 percent say they don't have enough money for a "real vacation" and 47 percent say their work-life is too busy to enjoy time away.
All developed countries have laws requiring paid vacation days except the United States. Japan and Canada require 10 days of paid vacation, while Finland and France have laws requiring 30 days of paid vacation, the Organization for Economic and Co-operation and Development says.
No survey details were provided.