October 16, 2010
PART I – DEFINITION AND CAUSES OF CHRONIC INSOMNIA
This is part one of a four part series on understanding and treating chronic insomnia.
Insomnia Quiz- Part I
1. True or False: The amount and quality of our sleep can affect hormones related to craving food and satiety.
2. True or False: Animals can die from extended sleep deprivation.
Answers to quiz and explanations provided at the end of this article.
Definition of Insomnia
The general definition of insomnia can be quite simple – the inability to initiate or maintain restorative sleep. When we use this definition, insomnia is the most common sleep problem in the industrialized world and roughly 30%-40% of persons complain of insomnia at some point in their lives. Although concise, this definition tells us little about the significance, cause, or prognosis of the insomnia. Over the past few decades, researchers have attempted to clarify the definition in several ways. The Fourth Edition of Diagnostic and Statistical Manual (DSM-IV) of the American Psychiatric Association specifies that the insomnia occurs for at least one month and causes impairment in function, and is not due to other medical, psychiatric, or sleep disorders. When the DSM-IV criteria are added, the prevalence estimates drop to about only 6%. Even more specific criteria are defined in the Second Edition of International Classification of Sleep Disorders (ICSD-2). According to the ICSD-2, insomnia is one of eight categories of sleep disorders. Within the ICSD-2 category of insomnia, there are several specific types including acute insomnia, paradoxical insomnia (sleep state misperception), behavioral insomnia, and psycho-physiological insomnia, to name a few. Recognition of these subtypes is useful because each has unique causes and specific treatments that may be effective.
Although there are no universally accepted criteria for defining the presence of insomnia, I generally use the following two specific thresholds to identify persons who may benefit from treatment for insomnia:
1. Difficulty falling or staying asleep at least 3 times per week, for at least 1 month:
- Delay of 30 minutes or more to fall asleep, or
- Awake for 30 minutes or more during sleep period; and
2. Daytime consequences of disrupted sleep:
- Fatigue, sluggishness, or
- Somatic complaints, or
- Stress about poor sleep, or
- Mood disturbances, or
- Poor concentration, or
- Impaired performance
Factors that Cause and Maintain Insomnia
If you ask an endocrinologist about what causes insomnia, she’ll probably tell you about the involvement of the hypothalamic-pituitary-adrenal axis, levels of adrenocorticotropic homorone and cortisol, the biochemical factors associated with aging and gender, diseases, etc. Ask a sociologist about what causes insomnia and he may inform you about the impact of industrialization including light pollution, noise pollution, stress associated with increased demands and expectations, etc. In reality, all of the different factors are relevant because sleep is a fragile bio-rhythm affected by many things in our lives. Thus, there are probably an infinite number of causes of insomnia, and we are all likely to experience insomnia at some point in our lives.
According to the cognitive behavioral model of insomnia, regardless of the specific factors that may have initially caused the insomnia, there are often common factors that are likely to maintain insomnia. These factors are described below.
Environmental Factors: There are many environmental factors that can influence your sleep. Some of the more obvious ones are noise, light, comfort of your bed, and compatibility with bed partners’ sleep routines. Other factors that are less apparent but equally important include temperature, consumption of food, activity, and perceived presence of danger. Especially important for behavioral insomnia are social pressures to stay awake so that we can interact (e.g., texting or chatting online), attend events (e.g., parties) or meet demands of work.
Homeostatic Pressure: Homeostatic pressure is the desire for sleep that develops by being awake over time. It is similar to the concept of hunger that develops by not eating over time. If you eat a larger meal with more calories, you will not be hungry for a longer period of time after the meal. Likewise, if you sleep for a longer period, you will not be sleepy for a longer period of time when you awake. Homeostatic pressure is affected primarily by how much you sleep – when you sleep less, it builds and when you sleep more, it decreases. Among persons with healthy sleep, homeostatic pressure increases and decreases predictably and rhythmically on a daily basis.
Circadian Rhythm: The circadian rhythm is a biological rhythm that interacts with cues in the environment (zeitgebers) to regulate our daily sleep and wakefulness. It helps us wake up and fall asleep around the same time each day, but also allows us to adjust to normal variations or big changes such as relocating to a different time zone. The benefits of the rhythm can be strengthened by maintaining a consistent sleep wake schedule and exposure to bright light. Aligning the circadian rhythm with the rhythm associated with homeostatic pressure can also help to achieve and maintain healthy sleep patterns.
Conditioned Arousal: Conditioned arousal refers to learned associations between cues in the environment and levels of arousal. When you experience insomnia, cues in the bedroom environment can become associated with feeling alert, or even frustrated. As a result, it’s likely to begin feeling more physiologically aroused as you prepare for sleep or when you wake up during your normal sleep time. Fortunately, you can learn relaxation strategies to decrease your levels of arousal and develop new behavioral strategies to decrease the associations with cues in your environment.
Attitudes About Sleep: As insomnia continues, you may understandably develop more negative attitudes about sleep. It is common to believe that you are losing control, you are unable to improve your sleep, or to feel like giving up on making changes. If left unchecked, these negative attitudes can increase your level of arousal and discourage you from seeking and continuing with effective treatments. Therefore, learning to recognize and challenge unhealthy attitudes can be critical for your success with overcoming insomnia.
Answers to Quiz
1. True. Getting less quality sleep increases a hormone level that induces craving for high calories foods (ghrelin) and decreases a hormone level that signal we are full from eating (leptin). Therefore, healthy sleep can be critical for maintaining healthy body weight.
2. True. Animals that are deprived of sleep for extended periods die. Sleep is an essential need for survival, similar to other needs such as water, food, and shelter.