cious extra minutes of sleep, she was still so exhausted by late afternoon that she could barely keep her eyes open. One day last fall, as her son played in the den of their Long Island, N.Y., home, Yasso's eyelids got heavier and heavier. Just before she nodded off completely, she felt her son's hands on her face. He was shouting, "Mama, Mama! Wake up!" That was the turning point. "I knew it was something more than just being tired because of everything a mother does as CEO of the family," says Yasso, 36. She called her doctor, who referred her to the NYU Sleep Disorders Center. After a night in the sleep lab, with electrodes monitoring her brain waves, breathing and movements, Yasso finally understood what was behind her overwhelming fatigue. NYU pulmonologist Ana Krieger told Yasso that during the eight hours she thought she was asleep, she had actually awakened 245 times. "That number shocked me," Yasso says. "But it also explained a lot."

Krieger gave her a diagnosis: she was suffering from recurrent episodes of hypopnea, which means her air flow decreases while she sleeps. Yasso's brain automatically rouses her whenever her impaired breathing reaches a critical point. That accounted for many of the awakenings. Krieger said the monitors also showed that Yasso has what's known as periodic limb-movement disorder. At night, her legs twitch involuntarily, which disturbs her sleep even more. Yasso was relieved. "It had a name and I was hopeful that it could be treated," she says. Several weeks later Yasso was back at NYU to be fitted with a machine called CPAP (for continuous positive airway pressure) that would keep her breathing steadily throughout the night. If CPAP resolves Yasso's hypopnea, as Krieger expects, the next step will be tackling the movement disorder. Already, Yasso says, she feels better just knowing that help is on the way.

Yasso is the grateful beneficiary of a radical rethinking of women's sleep problems. Until the early 1990s, the typical patient in a sleep lab might have been a middle-aged overweight man whose snoring was driving his wife crazy. But now those guys (and there are still plenty of them) are joined by more and more women of all ages who are also trying to figure out why they're among an estimated 70 million Americans who suffer from sleep problems. In recent years, there has been a growing recognition—by doctors and patients—that what might seem like simple new-mom fatigue or menopausal angst could actually be a physical or psychological problem that can be relieved with changes in sleep routines, medication or devices like CPAP. In fact, says Dr. Barbara Phillips, professor of medicine at the University of Kentucky and chair of the board of the National Sleep Foundation, "Women are more likely than men to have insomnia and sleep complaints at every age" except childhood.

You can blame some of those yawns on the complexity of modern women's lives. They're workers, wives, mothers and caregivers to elderly parents—all of which add up to stress and anxiety that don't stop when the lights go out. Long-term sleeplessness takes a toll. "With lack of sleep, you're more likely to have a lower mood, less energy, more irritability," says sleep expert Eve Van Cauter, a professor of medicine at the University of Chicago. Women who are sleep-deprived are also at risk for a range of problems: depression, heart disease, even obesity. Researchers have found that lack of sleep disrupts the production of hormones that regulate feelings of hunger and satiety. Many recent studies show that women (and men) who get less sleep are fatter.

The craving for sleep has fueled a huge demand for sleeping pills—with more than $2 billion in annual sales, according to IMS Health, a pharmaceutical information and consulting company. Expect more options in the next few years. Drug companies are working hard to target areas of the brain that induce sleep. But taking a sleeping pill can actually make it harder to find out what's really going on. "People are starting to think about these things as though they are painkillers you take for a headache," says Dr. Meir Kryger, author of "A Woman's Guide to Sleep Disorders." "I personally don't think it's a good development." Kryger says a patient should get a diagnosis before starting any treatment, and sleep medications should never be the first or only line of defense. Although the current generation of drugs—products such as Ambien, Lunesta and Rozerem—don't have the addictive potential of the older sleep medications, patients need to follow their doctors' instructions carefully. These drugs work best to help people get over short-term sleep problems, such as after the death of a family member or some other stressful event.

Sleeping pills don't resolve the underlying issue—whether it's stress, a physical disorder or hormonal changes. Women are most vulnerable to insomnia when they first begin menstruating, during pregnancy and around the time of menopause, says Dr. David Neubauer, a psychiatrist and associate director of the Johns Hopkins Sleep Disorders Center. Young girls just starting to menstruate have hormonal fluctuations and may have iron deficiency, which can affect sleep. Later on, hormone-related sleep problems become more common. According to a poll by the National Sleep Foundation, about 70 percent of menstruating women of all ages say that their sleep is disrupted during their periods by symptoms like tender breasts, bloating, cramps and headaches. Most of these are only temporary and can be treated with over-the-counter painkillers or by cutting down on caffeine. During pregnancy, women often have trouble staying asleep because of nausea, backaches, frequent trips to the bathroom and heartburn. Again, these are temporary, and discomfort varies by trimester. Simple remedies—supportive pillows, taking naps, avoiding spicy food—can make those nine months a little less difficult.

At menopause, many wom-en say hot flashes and night sweats ruin their sleep—although recent research suggests the brain mechanism behind these arousals may be more complicated. In any case, women often find relief by using fans or air conditioners at night, wearing lightweight pajamas and keeping some cold water on the night table. Hormone therapy may also work for some women, although there are risks.

But fluctuating estrogen isn't the only culprit. As scientists learn more about the nature of sleep itself, they're beginning to identify and treat specific sleep disorders in women. One of the most common is apnea, in which people stop breathing briefly during sleep. "There was this belief out there that apnea was a man's problem, and it isn't," says Kryger, a professor of medicine at the University of Manitoba. Loud snoring often accompanied by gasping sounds is a major symptom of apnea. Many women who snore are too embarrassed to tell their doctors about it, Kryger says, because snoring is seen as a masculine trait. But that reluctance hurts their health because they don't get the help they need.

Apnea becomes more common in women after menopause, when many gain some fat in their neck. That can be enough to obstruct breathing. Younger women with apnea are often overweight or have an abnormal facial structure, says Kryger. Pregnant women can also develop snoring and other characteristics of apnea as the baby pushes up on the mother's diaphragm; they should be monitored to make sure they aren't developing high blood pressure. Treatment for apnea may be as simple as using CPAP, but in other cases, patients get better by losing weight or simply sleeping on their sides instead of their backs. That side position tends to keep the airway open.

Another sleep disorder gaining new attention is restless-legs syndrome, which afflicts more women than men. Patients feel an unpleasant creepy or crawly sensation in their legs. "Some describe it as if worms were crawling inside their veins or ants were running up and down," says Kathryn Lee, professor of nursing at the University of California, San Francisco. That sensation is accompanied by an irresistible urge to keep the legs moving or walk around, says Lee. Restless legs are associated with low levels of serum ferritin, the storage form of iron. Those low iron levels—which may be caused by heavy menstruation or pregnancy—could explain why restless-legs syndrome is more prevalent in women. Excessive blood donation or a vegetarian diet can also sometimes lead to iron deficiency, Kryger says.

Scientists don't completely understand how low iron triggers restless legs, but current theories center on neurons in the brain that require lots of iron, including those that make dopamine, a brain chemical. Too little iron disrupts the dopamine system, says Dr. Christopher Earley, an associate professor of neurology at Johns Hopkins School of Medicine who studies restless-legs syndrome. Restoring iron usually resolves the problem, but that can take many months, depending on the severity of the iron loss. Last year doctors got a new weapon when the FDA approved the first medication specifically for restless legs, Requip. It works by stimulating dopamine receptors in the brain, an effect also used to treat Parkinson's disease. Women with restless legs often also have periodic limb-movement disorder, Yasso's diagnosis. "Whether it's a variant of restless-legs syndrome isn't clear," says Earley.

If a medical exam rules out a physical disorder, women often get more rest when they improve what doctors call "sleep hygiene." Basically, that covers everything involved in the process of getting to bed. "A huge amount of insomnia is induced by behaviors that can be quickly fixed," says Dr. Jean Matheson, medical director of the Sleep Disorders Center at Beth Israel Deaconess Medical Center in Boston.

When Matheson and other sleep doctors first see a patient, they take a sleep history. "People think night just happens," says Matheson. "But the way you sleep is often reflective of your health and activities during the day: how you wake up, what the room is like, what you do when you get up, when you have coffee, your routine when you come home." Sleep experts say you should use the bedroom only for sleep and sex—not as an auxiliary office or entertainment center with the TV blaring into the night. Take a hot shower before bed and keep your room cool (the temperature change induces sleepiness). Try to relax just before bedtime. Don't do anything that might raise anxiety—like paying bills or watching a horror movie. Go to bed and wake up at the same time every day, even on weekends. If you vary those times more than 90 minutes, you can mess up your sleep-wake cycle. Try to lower the lights as you get ready for bed and get some bright sun in the morning to let your brain know when it's night and day. Don't use alcohol to help you sleep. And, perhaps most important in the age of Starbucks, cut down on caffeine—especially in the afternoon and evening.

Finally getting the rest you need is worth extra effort. Alison Forsythe, 30, had trouble sleeping for a long time, but last year things got so bad that she was waking up almost every hour. "The more I couldn't sleep, the more frustrated I got—which made it even harder to fall asleep," says Forsythe, the director of marketing for United Way of Tri-Counties in Massachusetts. Her doctor referred her to the Beth Israel Deaconess sleep center, where she and her doctor zeroed in on congestion caused by her allergies. A new allergy medication as well as a hypoallergenic mattress pad and pillow did the trick. Now she says she's "sleeping like a baby." That's the ending we all dream about.

With Anne Underwood and Karen Springen