FRIDAY, Aug. 1 (HealthDay News) -- When American men spend long hours at work, their wives often pick up the slack at home by quitting their own jobs, but a new study shows the reverse is rarely true.

Men aren't any more likely to stop working when their wives begin to spend 60 hours a week or more on the job, said lead researcher Youngjoo Cha, a doctoral candidate in sociology at Cornell University.

"Women are more likely to sacrifice their careers, because men's careers are considered to be more important, and the culture of taking care of children says that mothers should bear the primary responsibility for housework and health care," Cha said.

She believes more women may choose to quit their jobs, harkening back to a time when fewer women worked outside the home, and men were more likely to be breadwinners.

In the new study, Cha looked at a 1995-2000 U.S. census survey of married couples. She was expected to report her findings Friday at the American Sociological Association annual meeting, in Boston.

She found that if a man worked more than 60 hours a week, his wife was 44 percent more likely to quit her own job. But when women worked more than 60 hours a week, their husbands weren't any more likely to quit their jobs.

Women with children were especially likely to quit their jobs if their husbands were putting in many hours at work. These professional women were 90 percent more likely to quit working if their husbands worked more than 60 hours or more a week compared to women without children.

"Even among very egalitarian couples, children are considered to be the woman's primary responsibility," Cha said.

Among professionals, 30 percent of husbands worked more than 50 hours per week, compared to just 12 percent of wives.

According to previous research, about 12 percent of American employees report working more than 50 hours per week, up from 9 percent in 1983.

Even after she adjusted the statistics to account for factors like education levels and income, the gender differences remained, Cha said.

Overall, the study findings suggest that "men's careers are comparatively more important than women's careers," Cha said.

Christine Percheski, a sociologist at Harvard University, said the study findings are plausible, although her own research suggests that the workload of husbands is having less of an effect on wives than in the past.

"This highlights how difficult it can be for couples in which both spouses have demanding careers," she said. "It's especially hard for women."

Is American society moving back toward the days when men were breadwinners and women stayed at home? Percheski doesn't think so.

"I don't think there's evidence that we're reverting to more traditional patterns," she said. "Women are working more than ever and bringing in more family income than ever."

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Learn more about families and work from the Families and Work Institute.