Abstract
Sleep complaints are prevalent among older adults. Sleep quality and quantity changes with advancing age. There are changes in sleep patterns that are normal with ageing but many changes are the sign of disordered sleep. Sleep can be divided into rapid eye movement (REM) sleep and non-rapid eye movement sleep (NREM). Each has unique characteristics that are differentiated by their waveforms on the electroencephalogram (EEG) and by other physiological signals; several physiological age-related changes are thought to produce alterations in circadian rhythms. While there are numerous psychological and social factors contributing to quality and quantity of sleep, specific sleep disorders more prevalent in old age are insomnia, sleep apnea, and rapid eye movement disorder. Non-pharmacological treatment is effective in management of sleep disorders. Cognitive behaviour therapy is most effective to tackle insomnia. Cognitive behavior therapy along with meditation is beneficial for other sleep disorders and a new technique is also emerging: mindfulness.
TopIntroduction
Sleep is a process in which important physiological changes (i.e. shift in brain activity, slowing of basic bodily functions) are accompanied by major shifts in consciousness (Barron, 2001). The pattern of sleep progression is called sleep architecture. Markov and Goldman (2006) reported two types of sleep architecture, rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. NREM sleep is characterized by a reduction in physiological activity. As sleep gets deeper, the brain waves measured by electroencephalogram (EEG) gets slower and have greater amplitude, breathing and heart rate slow down, and blood pressure drops. The NREM phase consists of four stages. When an individual is awake and alert, EEG contains many beta waves, relatively high frequency (14-30 cycles per second or Hz) low voltage activity. During the transitions between wakefulness and sleep, beta waves are replaced by low-voltage(amplitude) rhythmic alpha activity(8-13Hz). As the individual fall asleep and enter into stage 1 sleep, these alpha waves are replaced by low voltage mixed frequency (4-8Hz) theta waves. In stage 1, muscle activity is diminished from that of wakefulness, asynchronous eye movements are present for the first few minutes and the individual may be easily aroused as this is the most “shallow” of all aspects of sleep (Erwin et al, 1984). After spending about 10 minutes in stage 1, individual enters into stage 2 sleep, which is marked by sleep spindles and K complexes. Sleep spindles are short bursts of 12 to14 Hz wave forms for the duration of 1.5 seconds occurring 2 to 5 times per minute. They reduce brain sensitivity to sensory input which helps to enter deeper stages of sleep. K complexes are sudden, sharp waveforms that occur once in a minute and it may help in remaining asleep. The arousal threshold is increased in stage 2 sleep, muscle tone declines and no eye movements are seen. After that sleep enter into slow wave stage 3 followed by stage 4 which is marked by EEG pattern consisting of synchronized high amplitude (>75μV) and slow (0.5-2 Hz) delta waves.EEG activity during stage 4 is characterized by a greater amount ((>50%) of delta waves compared to stage 3 (20-50%). Slow wave sleep (SWS) is considered the deepest stage of sleep as it has a much higher arousal threshold, eye movements are not observed and muscle tone continues to decline.
Table 1.
Stages of sleep pattern in the EEG wave forms
| Wakefulness | Low voltage, mixed frequency activity Alpha (8-13cps) activity with eye closed. |
| Stage 1 | Low voltage, mixed frequency activity Theta (3-7) Activity vertex sharp waves |
| Stage 2 | Voltage mix frequency background with sleep spindles (10-14 cps bursts) and K Complexes (negative sharp waves followed by positive slow waves) |
| Stage 3 | High-amplitude (≥75µV) slow waves (≤ 2 cps) occupying 20 to 50 percent of epoch |
| Stage 4 | High amplitude slow wave occupy > 50% of epoch |
| REM sleep | Low- voltage mixed frequency activity, saw tooth waves, theta activity and slow alpha activity |
Key Terms in this Chapter
Circadian Rhythms: Refers to the daily rhythms in physiology and behavior that oscillate once approximately every 24 hours. The rhythms are generated by neural structure in hypothalamus; those functions work like a biological clock. The sleep wake cycle is one of these rhythms.
Sleep-Wake Cycle: Refers to the biological pattern of alternating sleep and wakefulness. The sleep-wake system is thought to be regulated by the interplay of two major processes, one that promotes sleep and one that maintains wakefulness. This cycle is roughly 8 hours of nocturnal sleep and 16 hours of daytime activity in humans in a single day.
EEG Brain Waves (Electroencephalogram): A record of electrical activity within the brain. EEG plays an important role in the scientific study of sleep.
Cognitive Behaviour Therapy: A form of cognitive therapy that focuses on changing illogical pattern of thoughts. It is useful in many mental and physical health problems.
Sleep Apnea: A sleep disorder characterized by repetitive collapse of the pharyngeal airway (interrupted breathing) during sleep due to which the patient wakes up many times.
Sleep Architecture: Represents the predictable cyclical pattern of sleep, alternating between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. It occurs throughout the night consisting of four NREM phases and one REM phase.
Insomnia: Has been historically defined by patterns of inappropriate wakefulness that occur during the sleep period. It is a disorder involving the inability to fall asleep or maintain sleep.