Asthma and the microbiota, how are they linked?
Asthma is a common chronic respiratory disease that affects both adults and children. Over 260 million people suffer from the disease worldwide1 and it is the most common chronic disease in children.1 Uncontrolled asthma, the most debilitating form of the disease, has serious consequences for patients’ day-to-day lives. The discovery that the gut, lung and nasal microbiota are involved in the development of asthma opens up new therapeutic avenues. Explanations below.
About this article
What is asthma?
Asthma is a chronic disease of the respiratory system that manifests itself as coughing, wheezing, shortness of breath, tightness in the chest, or a combination of these symptoms.1 Symptoms are caused by a narrowing of the airways in the lungs due to inflammation of the bronchi.1 Asthma attacks occur more frequently at night or during physical activity and the severity and frequency of attacks vary from patient to patient.1
Predispositions and triggers for asthma
Asthma is a complex multifactorial disease. It can develop due to a genetic predisposition (allergic background) and/or exposure to environmental factors such as allergens (pollens, mites), tobacco smoke or air pollution. Strong emotions, cold air or physical exercise can also trigger attacks. Lastly, individual-specific factors, such as an infection, or even obesity, can also come into play.2
Link with the microbiota?
Numerous studies note the role played by the various microbiota in the disease:
Reduced gut microbiota diversity, i.e. an imbalance in gut microbiota composition (known as (sidenote: Dysbiosis Generally defined as an alteration in the composition and function of the microbiota caused by a combination of environmental and individual-specific factors. Levy M, Kolodziejczyk AA, Thaiss CA, et al. Dysbiosis and the immune system. Nat Rev Immunol. 2017;17(4):219-232. ) ), in the first years of life is associated with an increased risk of developing asthma later in childhood.3 Some researchers believe that analyzing an infant’s gut microbiota could predict the risk of developing the disease.4 One factor behind such imbalances that has received much attention is the impact of antibiotics taken in the first weeks or months of life, i.e. when the gut microbiota and immunity are developing.5 Some studies have shown a link between antibiotic use and an increased risk of asthma later in childhood.6 Moreover, one research team has recently suggested that a gut dysbiosis in infants exposed to antibiotics may be responsible for childhood asthma.7 However, this mechanism has yet to be confirmed.
The lung microbiota is also thought to play a role, and although our understanding in this area is still very limited, it is a rapidly expanding field of research.8 The discovery of a unique lung flora with signatures specific to patients suggests a role in asthma.9,10 Furthermore, it appears that respiratory function in moderate to severe asthma is associated with the degree of lung inflammation and the composition of the microbiota.11,12 While research to confirm these results is ongoing, characterizing the bacterial populations living in the lower respiratory tract may help improve patient management or even better predict attacks.10
Data relating to the nasal microbiota are also very limited. However, an imbalance in the composition of the nasal microbiota has also been associated with the disease,13 and even with the severity of attacks,14 although no causal relationship has been established. Lastly, as with the gut microbiota, a very recent study on 700 children suggests that an alteration of the nasal microbiota due to antibiotic treatment before the age of 1 could explain the onset of childhood asthma at 7 years of age.15 However, this remains to be confirmed.
Living with asthma: treatments and solutions?
Although asthma cannot be cured, there are treatments that allow asthma patients to lead normal and active lives. Symptomatic treatments mainly limit the intensity of acute attacks by opening the bronchi, while disease-modifying treatments reduce inflammation of the airways, thus improving respiratory function and reducing attack severity.1
Studies on the relationship between the microbiota and asthma suggest that modifying the microbiota could help prevent the disease, leading researchers to focus their efforts on the use of probiotics and prebiotics.16,17 Their use as a treatment for the disease is also being studied.18
Are there any protective factors?
Exposure to (sidenote: Microorganisms Living organisms that are too small to be seen with the naked eye. They include bacteria, viruses, fungi, archaea and protozoa, and are commonly referred to as “microbes”. What is microbiology? Microbiology Society. ) during early childhood seems to help prevent asthma. Contrary to popular belief, living in a sanitized environment does not necessarily protect against respiratory diseases. Some studies show that house dust is not necessarily a risk factor for the development of the disease,19 while others have shown a decreased risk of asthma in children born and raised in the countryside20 or with pets.21
This article is based on scientifically approved sources. However, if you or your child display symptoms, please consult your family doctor or pediatrician.
1 World Health Organization. 2021. Asthma. World Health Organization, Geneva, Switzerland. https://www.who.int/news-room/fact-sheets/detail/asthma
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