Insomnia and the Importance of Sleep
Insomnia is often used synonymously with the word “sleeplessness”. However, insomnia is a clinical term used by medical professionals to identify individuals affected by “…the presence of a long sleep latency, frequent nocturnal awakenings, or prolonged periods of wakefulness during the sleep period or even frequent transient arousals”.
Insomnia affects people of all ages, although it is more common in older adults, females and those with medical/mental illness. It has been estimated that chronic insomnia affects anywhere between 10-30% of the population, and in certain cases up to 50-60% of the population. Thus, chronic insomnia is highly prevalent in the population, negatively impacting the quality of life of many whom we know in our lives. Sleep is immensely important for our overall health and wellbeing, and can result from a combination of biological and environmental factors. Some examples of biological factors include menopause, menses, physical health factors while environmental factors include working night shifts, chronic anxiety/stress, exposure to blue light, consumption of stimulants such as caffeine, and so forth. Although traditionally, sleep quality has been attributed to the activities in the brain, there is increasingly more research which reveals that the gut also plays an important role in modulating our sleep cycle and influencing our sleep quality.
Inadequate sleep has been shown to negatively affect our physical, emotional and mental health. In fact, there is insurmountable evidence which demonstrates the significance of sleep in learning and memory, energy metabolism and weight, emotional stability, mental concentration, as well as protecting against cardiovascular and immunological diseases.
Studies have found different mechanisms through which gut health is a protective factor against insomnia and its adverse effects.
The Gut helps modulate our stress response through the HPA Axis
Stress and anxiety are known to cause and exacerbate insomnia. Maintaining a healthy gut environment can help increase our resilience to stress. This is because certain microorganisms in the gut have been shown to modulate our body’s stress response. In particular, certain probiotic strains such as Bifidobacterium infantis, found commonly in the gut of newborns, have been shown to reduce our body’s fight-or-flight response via the Hypothalamis-pituitary-adrenal (HPA) axis. In fact, studies have found that maternal licking and grooming of neonates (newborn mammals) during early stages of life may influence the neonates stress response as adults. This has led evolutionary biologists to hypothesize that maternal caregiving behaviour (licking, grooming) of early postnatal neonates has an important influence on “biobehavioural development” of their offspring through epigenetic programming. In humans, stress and anxiety is linked to intestinal dysbacteriosis (microorganism imbalance in the gastrointestinal tract)
Thus, certain beneficial microorganisms in the gut have been shown to help promote our resilience to stress.
The gut helps to modulate our circadian rhythm
Recent Studies have found that the gut plays an important role in modulating our circadian rhythm, our body’s internal clock which regulates our sleep-wake cycle. Interestingly, studies have found that our gut microorganism composition (as measured by the ratio of Bacteroidetes, Firmicutes) changes throughout the day, not only influenced by food intake, dietary pattern but also by gender, and according to our circadian rhythm. The genes of microorganisms in our gut interact with our circadian genes, which are responsible for regulating our circadian rhythm (sleep cycle). The circadian rhythm of the microbiota has been shown to drive the metabolic activity of our circadian rhythm genes in various animal studies. In humans, gut inflammation (as seen in many patients with Irritable Bowel Syndrome, Crohn’s disease and Celiac disease) has been strongly associated with insomnia, dysregulation in the circadian rhythm, affective disorders and metabolic diseases.
The Gut promotes resilience to stress through tryptophan metabolism
In the gut, the metabolism of tryptophan, a precursor of the feel-good neurotransmitter serotonin, has been found to influence behaviour. Trytophan is metabolized into 5-hydroxytryptophan and serotonin, which are involved with numerous metabolic functions, including regulating mood at the level of the central nervous system (with brain and spinal cord) as well as reducing inflammation. Our gut microbiota has been found to influence the tryptophan pathway an influence the production of neuroactive metabolites (molecules which affect nerve function). Thus, modifying gut microbiota composition his currently being explored as a therapeutic approach to treat disorders in the “serotonin-related brain-gut”, with significant implications in the treatment of insomnia.