Ponder this after having enjoyed – if you enjoyed – a few extra hours of leisure this Labor Day: Workers may be a nation’s lifeblood, but when too many work too much, the nation’s blood pressure will rise.

Combing through a survey of Californians, researchers at the University of California, Irvine, have established a long-suspected link between work and health in America – that people who put in long hours on the job are more likely to suffer from hypertension than those who work less. Add that finding to recent studies demonstrating that employees working overtime are far more likely to get sick or injured, that their rates of sudden cardiac arrest are higher and that women who put in longer work weeks smoke more, snack more and exercise less.

All told, the findings are enough to suggest that good hard labor may be a prescription for poor health. Now that the average U.S. work week has climbed to the top of the industrialized world, that devotion to work could cost Americans big time.

“Americans work really long, and we know this trend hasn’t been getting better, it’s been getting worse,” says Linda Rosenstock, dean of the school of public health at the University of California-Los Angeles. She directed the Labor Department’s National Institute for Occupational Safety and Health from 1994 to 2000. “It portends a bigger health burden down the line,” she says, and that will swell the nation’s $2 trillion expenditure on health care.

The latest bad news for workaholics comes from a study, published in the October issue of the American Heart Assn.’s journal Hypertension, which looked at the survey responses of 24,205 working California adults in 2001. Compared with employees in the state who worked fewer than 40 hours a week, workers who clocked more than 51 hours on the job were 29 percent more likely to have diagnosed high blood pressure. Even just a few hours of overtime – between 41 and 50 hours of labor a week – increased the risk of high blood pressure by 14 percent.

“Each step up increased the risk of having hypertension,” says Dr. Dean Baker, a study author and director of UC Irvine’s Center for Occupational and Environmental Health. “It wasn’t like you have to work a very high number of hours for this effect to occur.”

Among working Californians, overwork is hardly rare, he adds. About 18 percent of those surveyed said they worked more than 50 hours a week.

To doctors and public health officials intent on finding and treating the millions of Americans with undiagnosed high blood pressure, the study provides an important new clue. A patient’s long work hours are as powerful a predictor of high blood pressure as being male or being poor – both of which are significant and well-established risk factors.

The new study also found that clerical and unskilled workers had far higher rates of diagnosed hypertension – 23 percent and 50 percent, respectively – than did professionals, even when employees worked the same number of hours. That result, which is in line with established research, suggests that work that gives employees more control over their working conditions and greater mental challenges may have a protective effect against hypertension, authors of the study say.