Sleep deprivation is chronic in our culture. In the United States, a National Sleep Foundation survey revealed that two out of three people get less than the recommended eight hours of sleep per night; of that group, one out of three gets less than six hours of sleep. Sleep deprivation is one of the chief aggravators of stress. Lack of sleep increases levels of cortisol, a stress hormone. Sleep deprivation affects the immune system (depleting certain cells needed to destroy viruses and cancerous cells), promotes the growth of fat instead of muscle, and may speed up the aging process.

Cortisol is released by the adrenal gland in response to stress. It essentially is an alertness hormone that makes you take action. This is what causes you to be alert in important meetings, helping you close the sale or deal. The hormone will subside as the stressful event passes. Normally, cortisol declines before sleep as a way of preparing the body for the resting state. Conversely, cortisol increases in the morning to make you more alert.

A common reason people cut down on sleep is to make time for a workout before the day begins. It’s not unusual for many to rise at 5:00 A.M. in order to get exercise. This, according to sleep experts, only compromises health and increases stress.

Sleep involves two phases: rapid eye movement (REM) and non–rapid eye movement. REM sleep, researchers believe, is when we dream, an important component of mental health. Non-REM sleep is our deepest sleep. During this phase, the body resets various hormones and replenishes energy stores.

Roughly 50 percent of people diagnosed with depression get too much REM sleep and not enough deep sleep, the replenishing sleep. According to a study done at the University of Westminster in London, stress levels are actually lower in people who wake up later than 7:21 A.M.

One way to find more sleep is to schedule nap times. Napping after work for a couple of hours (or during the day if you work from home) can dramatically improve sleep deprivation. Avoiding alcohol and caffeine before bedtime also can help.