“Hush little baby, don’t say a word
And never mind that noise you heard
It’s just the beasts under your bed
In your closet, in your head…”
— Metallica, Enter Sandman
And to Metallica’s homage to The Sandman, we can add the wee beasties in our belly. Insomnia, sleep deprivation, and poor sleep quality are major risk factors for the development of many chronic diseases. These include conditions like obesity, metabolic syndrome, type II diabetes, autoimmune disease, cardiovascular disease, as well as mental health concerns such as depression.
Given the deep interconnections between the gut and brain through the gut-brain axis, a link between disorders of sleep and chronic disabilities and diseases should not be surprising. However, remarkably, in terms of emphasizing proper sleep as a powerful and cost-effective part of any healthcare solution, a simple fix such as this is often ignored. This is especially significant given that the evidence of insomnia in the general population is estimated at up to around 20%, or one in five people, with half of the cases being chronic in nature.
This week’s study adds evidence of the bidirectional nature of the gut-brain axis and the negative impact of insomnia on gut health.
- The study sought to examine the interaction between the human gut microbiota and insomnia.
- The study employed Mendelian randomization (MR) analysis incorporating the use of genome-wide association studies (GWAS) datasets on insomnia (N=386,533), and gut microbiota data from both the MiBioGen alliance (N=18,340) and the Dutch Microbiome Project (N=8,208).
- Gut microbiota abnormalities are associated with an increased risk of chronic disability and diseases such as allergies, obesity, metabolic syndrome, type II diabetes, cardiovascular disease, and a host of autoimmune diseases.
- Gut microbiota abnormalities are associated with an increased risk of neuropsychiatric pathologies such as cognitive impairment, depression, Parkinson’s disease, and Alzheimer’s disease.
- The researchers found 14 gut bacterial taxa that may increase the risk of insomnia and 8 gut bacterial taxa that reduce the risk of insomnia.
- The researchers also found that insomnia may cause an increase in the populations of 12 gut bacterial taxa and a decrease in the populations of 7 gut bacterial taxa.
- Specifically, the bacterial genus Odoribacter, was implicated as a potential causative force in the risk of developing insomnia.
The Caveat:
Changes to the human gut microbiome associated with sleep disturbances, including insomnia, are well documented. Patients suffering from insomnia exhibit changes in the quality and character of their gut microbiota, which includes not only bacteria but also viruses and fungi.[1] Such changes are also associated with evidence of increased systemic inflammation, as evidenced by increased levels of interleukin-6 (IL-6) in patients with primary insomnia.
Whilst the gut microbiome is dynamic, changing rapidly in response to stress and diet and more slowly over time with aging, a healthy gut microbiota generally includes the bacterial phyla of Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria, with Firmicutes and Bacteroidetes appearing to be co-dominant. Sleep deprivation, as well as sleep duration restriction and fragmentation, are associated with changes in the character and quality of the human gut microbiome.
This study provides increasing evidence regarding the deep interdependencies between mental health, physical health, and the health of our gut microbiome. Additionally, it emphasizes the bidirectional, conversational nature of the ever-present information exchange occurring via the gut-brain axis. This axis involves many roots of communication, including endocrine, neuronal, and immune signaling pathways. Such pathways, both directly and indirectly, contribute to the regulation of neurological function, learning, memory, and emotion.
Although all too frequently overlooked by healthcare professionals and virtually ignored within the media, proper sleep affords a powerful and incredibly cost-effective mechanism to improve overall health. Studies such as this one provide evidence on the power of the bidirectional information exchange, the “conversation,” that is our gut-brain axis. Our gut microbiome, the driver of the gut’s portion of the conversation – one’s gut feelings, as it were – is highly dependent upon what we choose to eat. This singular fact gives us great control as to the direction and outcome of this particular tête-à-tête. With that control for health and healing within our hands, like Metallica, “We’re off to never-never land….”
[1] (Matenchuk , 2020)
Additional references:
Baglioni C, Battagliese G, Feige B, et al. Insomnia as a predictor of depression: a meta-analytic
evaluation of longitudinal epidemiological studies. J Affect Disord 2011;135:10–9.
Morin CM, Buysse DJ. Management of insomnia. N Engl J Med. 2024;391:247–58.
