Physiology of Sleep
An understanding of normal sleep is essential in recognizing and effectively treating insomnia. Although individual sleep needs vary, between six and nine hours of total sleep are necessary to feel rested and refreshed and to have optimal daytime functioning. Polysomnography is not needed to evaluate typical insomnia in the clinical setting but provides valuable information on normal physiologic sleep.
Sleep is divided into five stages. Stage 1 is the initial stage, also known as “relaxed wakefulness.” Stage 2 is also relatively light yet makes up about 50% of total sleep time. Deep, restorative sleep takes place in stages 3 and 4. Rapid eye movement (REM) sleep occurs in cycles throughout the night. Some hypnotic agents affect the time spent in different stages of sleep.
Sleep is divided into five stages. REM (rapid eye movement) sleep and NREM (non-rapid eye movement) sleep, which is further divided into 4 stages. The usual time it takes to fall asleep is between 15 and 30 minutes. Stage 1 of NREM, also known as “relaxed wakefulness,” initiates sleep. Approximately 50% of total sleep time is spent in Stage 2, a relatively light sleep also known as alpha rapid-wave sleep. Hypnotic drugs typically increase time spent in Stage 2 sleep. Fifteen to twenty percent of total sleep time is spent in Stages 3 and 4, or delta sleep. Delta sleep is the deep, restorative sleep time during which immune function is fortified and growth hormone is secreted. Time spent in delta sleep diminishes as patients age; at 75 years old, the stage is often nonexistent. NREM sleep is essential for rest, rejuvenation and the maintenance of overall health. The significance of REM sleep is not as well known. The body increases time spent in REM if deprivation occurs due to drugs, disease or fragmented sleep. Cycles of REM sleep occur throughout the night, approximately every 90 minutes. Time spent in REM increases toward the last three to four hours of sleep.
Patient Assessment
Individuals with insomnia are often seen by many different healthcare providers and are treated for a variety of concurrent health conditions. Thorough patient assessment includes taking inventory of all medications and medical problems to determine possible causes of insomnia. Ma huang (ephedrine), phenylpropanolamine (Dexatrim), caffeine, and nicotine gum are just a few examples of stimulating drugs known to interfere with sleep. Other possible drug causes of insomnia are listed in TABLE 1.
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Table 1 |
| Alcohol Appetite suppressants Bupropion Caffeine Calcium channel blockers Corticosteroids Decongestants Dopamine agonists Fluoxetine Sertraline MAOIs Nicotine Theophylline Thyroid medications |
A discussion to determine the nature and duration of insomnia as well as any associated symptoms is the first step in managing the condition. Questions such as, “How long does it take you to fall asleep? How long are you able to maintain sleep? How do you feel the next day?” are all necessary in developing an individualized treatment plan. Awakening with sore limbs and overall less restful sleep can signify restless legs syndrome (RLS) or periodic limb movements during sleep (PLMS). Frequent awakenings accompanied by gasps for air may indicate sleep-disordered breathing or sleep apnea. These more serious primary sleep disorders require assessment and treatment by a sleep specialist. Empiric treatment of insomnia with hypnotics is dangerous for sleep apnea patients. Objective assessment of sleep by a family member or bed partner is optimal because individuals with chronic insomnia underestimate the amount of sleep they get and overestimate the time it takes them to fall asleep. Assessing functional ability associated with insomnia before and after treatment is essential in measuring the success of each therapeutic intervention.