According to the US National Sleep Foundation more than 50% of adults miss out on a good night's sleep. Sleep complaints whether short-lived or chronic are especially common in women and in older people.

An occasional bout of sleeplessness is usually nothing to worry about. Jet lag, concern about a work problem or a relationship, traumatic events such as the death of or separation from a loved one, or discomfort from an injury or illness can cause short-term sleep difficulties.

Chronic sleeplessness is more complex and may require medical help. When a sleep problem lasts for a month or more, we begin to pay for it - in daytime drowsiness, trouble concentrating, irritability, increased risk of falls and accidents, and lower productivity. Long-term sleep loss can also cause several physical and psychological conditions, including high blood pressure, heart disease, stroke, depression, and even sudden death.

How much sleep do we need? Some of us seem to do well with five or six hours a night, while others may need 10 hours to feel their best. Research suggests that eight hours is about right for most people.

Women's sleep troubles

Family and work stresses are the main reasons for tossing and turning at night. But certain factors that affect sleep are unique to women.

About one-third of women have difficulty sleeping at night during their menstrual periods; about one in six says that she sleeps poorly in the week before she menstruates. Discomfort and changing hormone levels may also disrupt sleep during pregnancy. Some women report that hot flashes disturb their sleep before and at menopause.

Postmenopausal women sometimes develop sleep apnea, a serious sleep disorder in which breathing periodically stops or becomes shallow during the night.

As we grow older, we tend to get sleepy earlier in the evening and wake up earlier in the morning, apparently because of a change in the 24-hour (circadian) body clock — a phenomenon known as advanced sleep phase. This is why many older people adopt an early-to-bed, early-to-rise pattern.

The amount of sleep we need does not decrease with age, but the ability to sleep does. Healthy older people sleep fewer hours and wake up more often during the night (see "Stages of sleep," below). Older people also get more light sleep and less deep, restorative sleep. By age 45, so-called deep sleep almost entirely disappears in most people.

Insomnia

Insomnia, the inability to fall asleep or stay asleep enough to feel rested, is the most common sleep disorder. More women have it than men, and it's more common in old age than in youth. You may need help with insomnia if it impairs your physical, social, occupational, or psychological function.

Short-term insomnia caused by jet lag, a change in work shift, or a stressful life event can lead to chronic sleep problems. An individual may come to expect trouble going to sleep and to associate the bedroom with not sleeping. Consequently, the approach of bedtime provokes anxiety and brooding over sleep loss, which further aggravates insomnia.

Before seeking professional help, check your sleep environment and change habits that might be thwarting a good night's sleep. Here are some ideas.

• Make your bedroom a haven for sleep. Reserve your bedroom for two purposes only: sleep and sex. Don't watch television, read, or do crossword puzzles in bed. Be sure the room is dark, quiet, and at a comfortable temperature (cool is better than warm). A "white noise" maker to mask extraneous sounds may help.
  
• Limit alcohol and caffeine. Alcohol may make you sleepy, but the effect wears off after a few hours, and then, you're likely to waken more easily. Avoid drinking caffeinated beverages from noon or mid-afternoon onward.
  
• Establish a regular bedtime. Go to bed at the same time each night, and get up at the same time every morning. Avoid napping.
  
• Wind down. Establish relaxing bedtime rituals, such as a warm bath (if hot flashes are not a problem for you) or a few minutes of reading in a comfortable chair or on the couch. Don't use this time to have potentially stressful conversations. Although regular exercise can aid sleep, avoid vigorous physical activity within three hours of bedtime.
  
• If you can't sleep, leave the bedroom. If you're still awake after 20 minutes, get up, and don't go back to bed until you feel sleepy.

These strategies won't work if your insomnia is caused by depression, pain, sleep apnea, or anything else that makes you too uncomfortable to sleep. Speak with your clinician about treating any such underlying conditions. Insomnia is also a side effect of many common medications, such as certain antidepressants and antihypertensive agents, bronchodilators, diuretics, and corticosteroids. Your physician may be able to prescribe a different medication or dosing schedule to treat your condition without interrupting your sleep.

If lifestyle approaches don't help relieve insomnia, you may want to talk to your clinician about sleep medications.

Stages of sleep

Sleep occurs in cycles, which are divided into four stages. Stage 1, the transition to light sleep, takes about 5 minutes; body temperature drops and muscles relax. Stage 2, the real beginning of sleep, lasts 35–40 minutes. At this time, heart rate and breathing slow down. Stages 3 and 4 are "deep sleep," when the sleeper is very hard to wake. Breathing becomes regular; blood pressure falls; pulse rate slows; and brain wave activity is very slow. Adequate deep sleep is needed to wake up refreshed.

A normal sleep cycle lasts about 90 minutes. On average, it takes at least four cycles to get a good night's rest. Each begins with progressively deepening sleep and ends in REM (rapid eye movement) sleep, when we dream most vividly. The deepest non-REM sleep tends to occur in the early part of the night. As we get older, we spend less time in deep sleep.

Snoring, sleep apnea, and sleep loss

About 8% of people who snore have a disorder known as sleep apnea. In the young and middle-aged, sleep apnea is much more common in men than in women, but after age 60, the sex ratio becomes nearly equal. About one in four women over age 65 has the disorder.

During sleep apnea, breathing stops repeatedly for a few seconds or longer every few minutes during the night. Age-related changes in the breathing passages are one cause. The soft palate gets longer, fat pads in the throat fill out, and muscle tone decreases, making the airway less rigid. As a result, airflow may become partially blocked. This is obstructive sleep apnea, the most common type. Central sleep apnea, which is much more rare, occurs when the brain fails to send the proper messages to the respiratory muscles. As carbon dioxide levels in the blood rise, the sleeper snores or gasps (often loudly) to get more air.

Treating sleep apnea. Clinicians usually advise patients to lose weight (if they're overweight), avoid alcohol and sedatives, and try different sleeping positions. It may help to avoid sleeping on your back. (Sewing a marble or golf ball into the back of your pajamas will keep you from rolling onto your back.) One very effective treatment for sleep apnea is continuous positive airway pressure (CPAP), which keeps the breathing passages open. Another option is a mouth guard that keeps the airway open by thrusting the jaw forward.

Restless legs

People with restless legs syndrome experience tingly, creepy feelings in their legs when they lie down to rest or sleep. The sensations can last for more than an hour and seem to be relieved only by movement. Although mainly a concern in the elderly - about 20% of people over age 80 have the syndrome - it also occurs in as many as 15% of women in late pregnancy. In a related problem, periodic limb movement disorder, the leg muscles contract involuntarily hundreds of times throughout the night.

Treating restless legs. Some people get temporary relief from warm baths, muscle relaxation exercises, cold or heat packs, or massage. Avoiding caffeine and alcohol and getting exercise may also help. More difficult cases may require drug treatment with levodopa (Dopar, Larodopa, others), combination carbidopa and levodopa (Sinemet), or other drugs that increase dopaminergic transmission, such as pramipelole (Mirapex) and pergolide (Permax). Although these drugs are also used for Parkinson's disease, restless legs syndrome is neither a form nor a precursor of Parkinson's disease. Talk to your doctor before taking any medications if you're pregnant.

Whether your problem is sleep apnea, restless legs, or garden-variety insomnia, you can take measures to improve your sleep, either on your own or with a clinician's help. Realise that some changes in sleep are normal over the years. But continued sleep deprivation can detract from a healthy, active life.