Health Update

Most people thought of sleep as a passive, dormant part of our lives. But it is during sleep that our brains are very active. Moreover, sleep affects our daily activities and our physical and mental health.

Getting to sleep is a 90-minute cycle. We usually pass through five phases: stages 1, 2, 3, 4, and REM [rapid eye movement] sleep.

These stages progress in a cycle from stage 1 to REM sleep, then the cycle starts over again with stage 1. Waking usually transitions into non-rapid eye movement (NREM) sleep. REM follows NREM sleep and occurs 4 to 5 times during a normal 8 to 9 hour sleep period.

The first REM period of the night may be less than 10 minutes in duration, while the last may exceed 60 minutes, explained Dr. Gil Gan of Metropolitan Medical Center, the resource speaker in the 188th medical forum, Sleep Disorders sponsored by the Association of AB Medical Scholars.

During stage 1, which is light sleep, we drift in and out of sleep and can be awakened easily. People awakened during this stage often remember fragmented visual images. Many also experience sudden muscle contractions often preceded by a sensation of starting to fall.

It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. People awakened during deep sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up. Some children experience bedwetting, night terrors, or sleepwalking during deep sleep, Gan said.

There are two groups of people with different sleeping habits: The evening type (owls) sleep late and wake up late, they are tired in the morning but perform best in the afternoon, and the morning type (larks) wake-up early, rested and refreshed, and work efficiently in the morning.

The amount of sleep each person needs depends on many factors, including age. Infants generally require about 16 hours a day, while teenagers need about 9 hours on average.

For most adults, 7 to 8 hours a night appear to be the best amount of sleep, although some people may need as few as 5 hours only. While there is an increased chance of death from coronary arterial disease, cancer or stroke for adults who sleep less than four hours per day or more than 9 hours per day, Gan explained.

Sleep deprivation affects the immune system in detrimental ways. Sleep appears necessary for our nervous systems to work properly.

Too little sleep leaves us drowsy and unable to concentrate the next day. It also leads to impaired memory and physical performance and reduced ability to carry out math calculations. Without sleep, neurons may become so depleted in energy or so polluted with by-products of normal cellular activities that they begin to malfunction.

Since sleep and wakefulness are influenced by different neurotransmitter signals in the brain, foods and medicines that change the balance of these signals affect whether we feel alert or drowsy and how well we sleep.

Caffeinated drinks such as coffee and drugs such as diet pills and decongestants stimulate some parts of the brain and can cause insomnia, or an inability to sleep. Many antidepressants suppress REM sleep, Gan said.

Source: Manila Bulletin