Indoor dust microbiota composition and allergic diseases: a scoping review to construct a reusable DAG

Abstract

Background: Exposure to dust microbial components is associated with disease and is highly relevant for public health since humans spend most of their time indoors.

Objectives: This scoping review aims to describe the characteristics of studies assessing the indoor dust microbiome, use of causal statements, methods for confounding variable identification, to develop a reusable directed acyclic graph (DAG), and to explore the feasibility and challenges of pooled microbiome analyses.

Methods: Scoping review of original research articles in the WoldCat database, using terms related to “indoor environments”, “dust”, and “microbiome”, published between 2000 and 2024. Descriptive analysis of characteristics and methods of studies. Available data with comparable dust collection methods were analyzed together in a pooled microbiome analysis. A reusable DAG was constructed following the evidence synthesis (ESC-DAG) method.

Results: This review includes 144 studies, 88.9% reporting bacterial dust microbiomes; 57.6%, fungal; and 6.7%, other. Most studies were conducted in dwellings (68.1%) and high-income countries (74.9%). Environmental characteristics (80.6%) and allergic diseases (28.5%) were frequently reported. Pooled microbiome analyses revealed higher comparability between studies sharing dust sample-processing methods, regardless of world region of sampling. Causally suggestive statements were identified in 81.9% of studies, leading to the attempt to develop of a reusable ESC-DAG (exposure: indoor dust microbiome, outcome: allergies).

Conclusions: Future research should expand beyond bacteria and fungi to include other microbial components, non-residential buildings, and low-to-middle income countries. The impact of comparable methods and metadata for pooled analyses could be further explored. Using DAGs has the potential to strengthen causal inferences of the indoor dust microbiome and health outcomes.