We often post information about exercise and nutrition as keys to health and longevity. One other important factor, that isn't discussed enough is sleep.

We have so many demands on our time-jobs, family, errands-not to mention finding some time to relax. To fit everything in, we often sacrifice sleep. But sleep affects both mental and physical health, and it's extremely vital to your wellbeing.

Of course, sleep helps you feel rested each day, but while you're sleeping, your brain and body don't just shut down. Internal organs and processes are still hard at work throughout the night, as sleep continues to service all aspects of our body like energy balance and intellectual function while we're in slumber.

When you're tired, you can't function at your best. Sleep helps you think more clearly, have quicker reflexes and focus better, and better-rested people therefore operate on a more efficient level than those who don't get sufficient sleep. Tired people tend to be less productive at work, and they're at a much higher risk for traffic accidents. Lack of sleep also influences your mood, which can affect how you interact with others. A sleep deficit over time can even put you at greater risk for developing depression.

But sleep isn't just essential for the brain. In actuality, it affects nearly every tissue in our bodies, including growth and stress hormones, our immune system, appetite, breathing, blood pressure and cardiovascular health.

Research shows that lack of sleep increases the risk for obesity, heart disease and infections. Throughout the night, your heart rate, breathing rate and blood pressure rise and fall, a process that may be important for cardiovascular health. Your body releases hormones during sleep that help repair cells and control the body's use of energy. These hormone changes can affect your body weight.

Recent studies also reveal that sleep can affect the efficiency of vaccinations, with one showing that well-rested people who received the flu vaccine developed stronger protection against the illness.

A good night's sleep consists of 4 to 5 sleep cycles. Each cycle includes periods of deep sleep and rapid eye movement (REM) sleep, when we dream. Although personal needs vary, on average, adults need 7 to 8 hours of sleep per night. Babies typically sleep about 16 hours a day, young children need at least 10 hours of sleep, while teenagers should get at least 9 hours. To attain the maximum restorative benefits of sleep, getting a full night of quality sleep is important.

Sleep can be disrupted by a number of factors. Stimulants such as caffeine or certain medications can keep you up, and distractions such as electronics-especially the light from TVs, cell phones, tablets and e-readers-can also prevent you from falling asleep.

As people get older, they may not get enough sleep because of illness, medications or sleep disorders. By some estimates, about 70 million Americans of all ages suffer from chronic sleep problems. The two most common sleep disorders are insomnia and sleep apnea.

People with insomnia have trouble falling or staying asleep. Anxiety about falling asleep often makes the condition worse. Most of us have occasional insomnia, but chronic insomnia-lasting at least 3 nights per week for more than a month-can trigger serious daytime problems such as exhaustion, irritability and difficulty concentrating.

Common therapies include relaxation and deep-breathing techniques. Medicine may also be prescribed, but you should consult a doctor before trying even over-the-counter sleep pills, as they may leave you feeling unrefreshed in the morning.

People with sleep apnea have a loud, uneven snore (although not everyone who snores has apnea). Breathing repeatedly stops or becomes shallow. If you have apnea, you're not getting enough oxygen, and your brain disturbs your sleep to open your windpipe.

Apnea is dangerous, as there is little air exchange for 10 seconds or more at a time. The oxygen goes down and the body's fight or flight response is activated. Blood pressure spikes, your heart rate fluctuates and the brain wakes you up partially to start your breathing again. This creates stress. Apnea can leave you feeling tired and moody, and you may have trouble thinking clearly.

If you have mild sleep apnea, you might try sleeping on your side, exercising or losing weight to reduce symptoms. A CPAP machine, which pumps air into your throat to keep your airway open, can also help. Another treatment is a bite plate that moves the lower jaw forward. In some cases, however, people with sleep apnea need surgery.

Several studies are being performed to gain deeper insights into sleep apnea and other aspects of sleep. One five-year study of 10,000 pregnant women is designed to gauge the effects of apnea on the mother's and baby's health, which will shed more light on apnea and the importance of treatment.

Good sleep is critical to your health. To make each day a safe, productive one, take steps to make sure you regularly get a good night's sleep. Keep this in mind every night before going to sleep. If your life and your sleep is interrupted by a muscle strain, ligament sprain, joint problem or movement disorder, always remember to see a physical therapist first and fast if you happen to experience any aches or pains in your joints or muscles during the day.