Who hasn’t felt cranky, unfocused, and loopy after a bad night’s sleep? Three-quarters of adults have “sleep difficulties” and more than half “often wake up not feeling refreshed,” according to a national poll. But the damage from sleep deprivation is even worse than you may think. More studies are finding that too little sleep can lead to a wide variety of potentially life-threatening conditions. Among them:

Obesity. Women who reported getting five hours of sleep per night were nearly twice as likely to be obese as women who regularly slept about seven hours; those who got four hours were three times more likely to be obese, according to a 2005 study of more than 2,500 women under age 49. Sleep restriction increases your appetite by lowering your levels of leptin, a hormone that suppresses hunger, and raising your levels of ghrelin, a hormone that stimulates it.

High blood pressure. People under age 60 who sleep five or fewer hours a night are twice as likely to develop hypertension as those who log seven to eight hours, according to a 2006 study of almost 5,000 men and women. Not sleeping enough strains the cardiovascular system and “resets” it to operate around the clock at an elevated pressure.

Diabetes. Studies have found an association between lack of sleep and a risk for diabetes as well as a 45 percent increased risk of heart attack and a 15 percent increased risk of death from all causes.

Women need to be especially concerned since they’re much likelier than men to have sleep problems. The reason, says a National Sleep Foundation survey: Many women are so busy caring for their families while holding down jobs that they don’t make rest a high priority,” says Meir Kryger, M.D., a past president of the American Academy of Sleep Medicine and author of A Woman’s Guide to Sleep Disorders. Even women who don’t suffer from sleep disturbances may steal their only “me” time from hours when they should be snoozing.

Are You a Problem Sleeper? Signs that you have a sleep deficit include taking more than 30 to 45 minutes to fall asleep; waking up many times a night; rousing after too few hours of sleep and being unable to return to sleep; waking up feeling tired and feeling sleepy throughout the day. Most people need seven to nine hours of sleep per night—but the real cue that you’re getting enough is waking up refreshed in the morning and feeling alert all day long. In addition, there’s no need to worry if you experience occasional sleep difficulties—say, a few times a month—that don’t interfere with your daily activities. Among adults with sleep difficulties, half those in the national poll reported that sleep problems resulted in “getting easily frustrated” or being unproductive. “It’s perfectly common to have problems sleeping every once in a while,” says David N. Neubauer, M.D., associate director of Baltimore’s Johns Hopkins Sleep Disorders Center.

When is a sleep problem classified as full-blown insomnia, the chronic inability to fall asleep or stay asleep? Starting to worry about it is one cue. Another is when the situation has lasted more than a month. Start by seeing your doctor, who will check for underlying health issues. If you’re otherwise healthy, he or she may suggest remedies. Or consider asking for a referral to a sleep specialist for an evaluation and techniques for your type of problem. “Treatment takes longer when insomnia lasts more than a year,” says Nancy Nadolski, M.S.N., a family nurse-practitioner in Boise, Idaho, who treats patients who have insomnia.