Despite managing two jobs, Donna Bosley admits, "Sometimes I get lazy. On weekends, I don't even want to get out of the chair to answer the telephone." Alex Holt cares for three teenage daughters and teaches special education students. She keeps her house clean and her classroom organized. Still, she confesses, "The other day I lost a book and a student's report card."

What's going on? Two busy women. Too common of a problem: Not enough sleep. More than 40 percent of Americans report they are so sleepy during the day that it interferes with daily activities at least a few days a month or more, according to a poll released by the National Sleep Foundation.

Not only can lack of sleep cause us to feel lazy or lose things, it can lead to serious consequences, such as falling asleep while driving. And fatigue takes a special toll on women, who typically manage full-time jobs, children's busy schedules, and more than their share of household chores.

So, how much sleep do you really need? Probably more than you think. Experts agree most adults require eight hours every night. Not seven, not six, but a full eight hours. How much sleep are most of us getting? According to the NSF, probably not enough. Most adults claim to sleep an average of 6.9 hours a night during the week. If you're between 18 and 29, chances are you sleep even less — this group averages less than six hours.

Losing an hour or two may not seem like much, but the results affect our performance. The recent NSF poll revealed that 51 percent of adults report that sleepiness on the job interferes with the amount of work they get done. Forty percent admit that the quality of their work suffers when they're sleepy, and at least two-thirds say that sleepiness interferes with their concentration and makes handling stress more difficult.

So what can you do? "Take sleep seriously," advises David Dinges, Ph.D., chief of the division of sleep and chronobiology at the University of Pennsylvania. "The effects of losing sleep are cumulative. If you only get six hours a night, by the fifth day your waking performance may be as if you didn't sleep at all."