On average, three of every ten Americans did not feel well-rested last night according to the CDC.

In general, men sleep better than women, and older, more affluent folks sleep better than younger and less affluent people. According to the National Institutes of Health, 50 to 70 million Americans are affected by chronic sleep disorders and intermittent sleep problems that can significantly diminish health, alertness and safety. Untreated sleep disorders have been linked to high blood pressure, heart disease, stroke, depression, diabetes, and other chronic diseases.

Sleep is divided into two basic types: (1) Rapid Eye Movement (REM), and (2) Non-REM sleep (NREM) which has three different stages.

REM sleep occurs roughly every 90 minutes with increased duration over the course of the night. During REM sleep dreams occur, breathing is more irregular, rapid, and eyes move more rapidly with eyelids closed. There is also a lack of skin reactivity and exceedingly low muscle tone.

NREM sleep has an initial transition stage from wakefulness to sleep; the brain and body relax, there can be jerking/twitching and this stage lasts only a few minutes.

The next stage of NREM sleep is further relaxation and a slowing of breathing and heart rate. This stage comprises about 50% of the NREM sleep.

The final stage of NREM sleep is the deepest sleep, from which it is difficult to awaken; there is no eye movement, very slow breathing, and lower heart rate. This final “deep” sleep is called Slow Wave Sleep, and it decreases with age.

If we don’t get enough sleep, we accumulate a “sleep debt” that can be difficult to “pay back.” It has been linked to health problems such as obesity and high blood pressure, negative mood and behavior, decreased productivity and safety issues at home, on the job or on the road. Sleep debt leads to fatigue, inattentiveness, and poor performance.

Without enough REM sleep, our body never achieves the restful state needed to function properly. Signs of unhealthy sleep include daytime sleepiness, depression, falling asleep at work, unpleasant moods, and fatigue.

As we age, we need less sleep. Newborns and infants sleep over 18 hours per day. This amount of sleep slowly decreases over childhood to the teenagers who need about 10 hours. Adults need anywhere between 7 and 9 hours.

There are four common sleep disorders: Sleep apnea, narcolepsy, insomnia, and restless leg syndrome.

Sleep apnea occurs in one of five adults in our country, most of whom are not diagnosed. Sleep apnea is a partial or complete collapse of the upper airway, in which a person stops breathing repeatedly during their sleep, sometimes hundreds of times during the night, often for a minute or longer.

Symptoms of sleep apnea are snoring, choking or gasping during sleep, excessive daytime sleepiness/fatigue, high blood pressure, weight gain or inability to lose weight, depression, sexual dysfunction, morning headaches, memory or learning problems and not being able to concentrate, feeling irritable, depressed, mood swings or personality changes, urination at night and a dry throat upon waking.

Risks for sleep apnea include obesity, male gender, older, positive family history, smoking, metabolic disorders, alcohol abuse, and sedative use. Untreated sleep apnea increases your risk of Type 2 diabetes, high blood pressure, heart disease, stroke, and further weight gain.

Lifestyle changes, mouthpieces, and breathing devices help—particularly continuous positive airway pressure machines. There are no medications that have proved to be efficacious, but consulting with a sleep specialist can help.

Narcolepsy—sleeping sickness—is a neurological disorder in which the brain can’t regulate sleep. People so afflicted unexpectedly fall asleep in the middle of the day for a few seconds or minutes, or even hours. Treatment is highly individualized but can be effective.

Insomnia includes having trouble falling or staying asleep. It is one of the most common medical complaints. Symptoms include daytime fatigue or sleepiness, irritability, depression, anxiety, poor attention span, increased errors and accidents, tension headaches, gastrointestinal symptoms, and ongoing worries about sleep.

Women, the elderly, stressed-out folks, workers who change shifts, and those with mental health problems, are most likely to suffer from insomnia. Transient insomnia is common and not a problem; persistent symptoms, however, should be addressed.

Restless leg syndrome (RLS) is characterized by the irresistible urge to move one’s legs. Involuntary, repetitive or periodic jerking of the limbs, a crawling sensation, or restlessness are all symptoms.

To sleep well you should stay on a consistent schedule even on weekends. Have a regular, relaxing bedtime routine, make your environment conducive to sleep, get comfortable, use your bedroom only for sleep and sex, stop eating two or three hours before bedtime, exercise regularly, and avoid alcohol and caffeine late in the day. And if you smoke, QUIT!

So much more is known and can be done to help achieve good sleep, yet insomnia remains under-recognized and under-treated. So have a good night’s sleep—if not, seek help.