How Age and Environment Shape Our Health

written by caroline cencer phd Feb 06, 2025

A deep dive into the respiratory microbiome

The upper respiratory tract (URT) includes the nose, throat, and upper airways and plays a crucial role in our respiratory health by defending against bacteria, viruses, allergens, and pollutants. As adults, we breathe in approximately 2,000 gallons of air daily, exposing us to the external environment. Luckily, the microbiome, or the collection of microorganisms, found within the URT composed of fungi, bacteria, and viruses, acts as a protective barrier — balancing immune responses, and preventing harmful pathogens from entering the lungs.

To date, most microbiome research has focused on its structure and role in the gut. However, the URT microbiome is just as important to study. Clinical studies have linked it to acute and chronic respiratory diseases, such as infections, asthma, and chronic obstructive pulmonary disease (COPD). Despite these vital connections, most URT microbiome research has focused on infants and children, leaving gaps in our understanding of how these microbial communities change as we age or how they are impacted by environmental factors such as lifestyle and community.

The Study:

In a groundbreaking study published in Cell, Odendaal and colleagues ambitiously sought to answer important questions about URT microbiome changes across the human lifespan. They aimed to map how microbiota composition changes with age and under the influence of different environmental factors. The authors’ overarching goal was to uncover how microbial changes may be linked to respiratory health.

The Methods:

The researchers collected 5,589 samples from 3,160 individuals in the Netherlands aged 0-87, analyzing samples from both the nasopharynx, which is the area of your upper throat behind your nose, and the mouth through RNA sequencing (Figure 1). This method allowed them to identify and quantify the bacterial species present in each sample. They divided participants into different age categories and collected detailed lifestyle, health, and environmental data through questionnaires. This study took a cross-sectional approach, focusing on a wide range of demographics which provided a snapshot of how microbiota are shaped by age, lifestyle, and health conditions.

Figure 1: Depiction of sample collection and processing from study participants. Adapted from Odendaal et al. Creative Commons Attribution-NonCommercial-No Derivatives License (CC BY NC ND)

The Results:

Age: The results of the study confirmed that age is a key factor influencing the types of organisms present in the URT microbiota. For instance, the researchers found that microbial diversity and density were lower in children (ages 0-14), but a few bacterial species such as Moraxella and Haemophilus, known to play roles in respiratory infections, were highly prevalent. This may in part explain why school-aged children tend to experience more URT illnesses.

Looking across older study participants, microbial diversity increased, with significant changes occurring up until early adulthood (ages 15-24), when the composition of the URT microbiota appears to stabilize. In older adults (age groups 40-64 and 65+), the nasopharynx microbiota was full of bacterial groups such as Corynebacterium and Dolgosigranulum pigrum, which are associated with respiratory health and protection against pathogens.

Figure 2: Diagram of the upper airway, pointing to relevant regions of the pharynx that were highlighted in this study. Made with BioRender.

Environment: Interestingly, the study revealed that environmental and lifestyle factors had region-specific effects. In the nasopharynx, environmental factors like season and social contact played a significant role. For example, people who lived or worked with children had microbiomes that more closely resembled those of children. In contrast, the oral microbiota was more heavily influenced by lifestyle choices, such as smoking and alcohol use. Smokers had less diversity and higher levels of harmful bacteria, while alcohol consumption was linked to higher microbial diversity in the oropharynx.

The study also found a strong association between respiratory symptoms (like runny nose and cough) and specific microbial changes. Bacteria like Streptococcus pneumoniae were more prevalent in individuals with recent respiratory symptoms or a history of pneumonia, suggesting that the URT microbiota might reflect or even contribute to the likelihood of infection.

Conclusions and Future Directions:

This large-scale study provided an in-depth look at how the URT microbiome evolves from infancy through adulthood and how host and environmental factors interact with these microbial communities. One of the key takeaways is that age plays a central role in shaping our URT microbiota. However, environmental and lifestyle factors also have significant influence, especially in specific regions. This new ‘map’ of the URT microbiome opens the door for personalized treatments, where factors like a person’s age, living conditions, and daily habits might guide measures for preventing infections and chronic diseases.

Looking ahead, the researchers suggest that future studies should ideally focus on following individuals longterm to track how the URT microbiome changes over time and how this may impact the individual’s health outcomes. Additionally, more research on how environmental exposures like pollution or diet may affect the URT microbiome could provide insights into new strategies for promoting respiratory health across the globe.

Written by Caroline Cencer PhD

Edited by: Sohani Ramnani

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