Insomnia: Classification and Pathophysiology

00:00 So let's talk a little bit more about insomnia.

00:05 First, let's start with a definition. Insomnia is the subjective perception of difficulty with sleep initiation, duration, consolidation, or quality despite adequate opportunities for sleep resulting in daytime functional impairment. So there are a number of things going on there. One, it's the patient's perception. They don't feel like they're sleeping enough or getting asleep or staying asleep. The second and critically important is the impairment in daily function. We all have better nights of sleep and worse nights of sleep, but we're able to function regardless of how we then slept and the consistent impairment in daily function is an important aspect of a diagnosis of insomnia. When we think about insomnia, we can classify it as acute beginning and occurring over less than 3 months or chronic, persisting over more than 3 months. Acute insomnia is transient and short-term.

01:03 It's often due to a number of triggers, perhaps environmental or a recent illness and usually associated with a change in anxiety or life events or social events or those sorts of things or a physical stressor. And it can evolve from acute insomnia into the chronic form of this condition. Chronic insomnia includes both primary and comorbid insomnia and we can also often see muscular weakness, hallucinations, or double vision which may be present in these patients as a result of this chronic and longstanding reduction in sleep. When we think about insomnia, we can classify insomnia by how sleep is impaired. So we think about sleep onset insomnia. This is a difficulty with falling asleep at the beginning of the night.

01:51 There is also sleep maintenance insomnia, which as it's described is difficulty with staying asleep. Patients are often able to get to sleep but the problem is maintaining consistent sleep throughout the night. Early morning awakening is insomnia as a result of early awakening, waking up too early and difficulty with getting back to sleep. And then finally, paradoxical insomnia, which is a sleep state misperception.

02:17 This is disassociation between the patient's self-reported quality of sleep and the findings from objective polysomnography which are normal. In terms of epidemiology, insomnia is not uncommon. At least 30% of patients report symptoms of insomnia at some point in their life. It's more common in women and older adults and there is an increase prevalence in those who are unemployed, divorced, widowed, or experiencing physical or emotional stressors. In terms of risk factors, inadequate sleep hygiene is one of the most important. Irregular bedtime schedules can contribute to insomnia. Using bed for work, eating, watching television can also contribute to insomnia. When the brain thinks it's going to do other things in bed, it's not prepared to sleep when you're there. Naps especially those after 3 pm can contribute to insomnia. And stimulating activities, exercising right before bedtime are all risk factors for the development and continuation of insomnia. There are a number of environmental factors that can contribute to insomnia, noise, lights, and extreme temperatures. Light is one of the critical wakefulness producing stimuli and so bright lights around bedtime or in bed can contribute to insomnia. Underlying sleep disorders like restless leg syndrome can also contribute to insomnia and when treated we can see insomnia improve. And then behavioral insomnia. Jet lag or shift worker's disorder can result in insomnia as a result of abnormalities in that typical circadian rhythm. When the brain isn't expecting to sleep and needs to sleep, this can contribute to insomnia.

04:03 And then finally, some medical conditions are associated with insomnia; diabetes, GERD, hyperthyroidism, asthma, Alzheimer's disease, menopause, and chronic pain. So when we think about managing insomnia and treating patients, we walk through things like sleep hygiene, environmental factors, underlying sleep disorders, behavioral changes, and medical conditions, and managing these can be important in our treatment and management of patients presenting with insomnia.

04:35 In addition, mental health disorders can contribute to insomnia; things like depression, anxiety, and posttraumatic stress disorder. Substance use and medication-induced insomnia is also an important consideration. Stimulants can cause insomnia and benzodiazepines or particularly withdrawal can also contribute to changes in sleep. So let's talk briefly about the pathophysiology. What's going on to contribute to insomnia? Well, there are a number of brain structures involved and wakefulness and sleep and abnormalities in the wakefulness centers or the sleep centers can contribute to insomnia. There are a number of neurotransmitters that play a major role in insomnia. Decreased inhibitory signals, reduced gaba in the brainstem reduce the brain's ability to get to sleep. Activation of the suprachiasmatic nucleus and inhibition of melatonin that's produced by the pineal gland can also contribute to alterations in wakefulness and contribute to insomnia. And then finally, increased levels of stress hormones like cortisol can alter the brain's ability to go to sleep or be awake and contribute to insomnia.