Mouldy area size and asthma symptom score and control in adults: the CONSTANCES cohort

Studies on indoor mould contamination and asthma in adults are scarce, although there is evidence of deleterious effects on childhood asthma. Associations between different mould contamination indicators and asthma were investigated in adults from the largest French prospective population-based cohort.

Participants completed standardized questionnaires: on visible mould and mouldy area size (0 m², spots, <0.2 m², [0.2 m²-1 m²], ]1 m²-3 m²] or >3 m²) in bathroom, kitchen, or main living quarters (living room, bedroom) in 2019, and on respiratory health (2019-2022). Associations between indoor mould with current asthma, asthma symptom score (sum of five respiratory symptoms in the last 12 months), and uncontrolled asthma (Asthma Control Test<20) were evaluated by zero-inflated negative binomial and logistic models adjusted for age, sex, smoking, education, dwelling type and French deprivation index. Sensitivity analyses: in subgroups, stratified by dwelling type or sex, and further adjustments for region, occupant-surface ratio, body mass index, occupant (owner/tenant) and rural/urban areas were performed.

Analyses included 28 596 adults (mean age: 55 years old, 55 % women, 70 % living in houses, 24 % reported at least one asthma symptom, 7.4 % current asthma of whom 15.1 % had uncontrolled asthma). Visible mould and mouldy area size>3 m² were reported by 21.2 % and 0.3 % of participants, respectively. Visible mould in dwelling was significantly associated with current asthma, asthma symptom score and uncontrolled asthma (OR and mean score ratio (MSR) around 1.40), stronger effect in the main living quarters. Mouldy area size was significantly associated with higher risk of current asthma (all ORs≥1.29, p-trend<0.001) and increased asthma symptom score (all MSRs≥1.32, p-trend<0.001). No heterogeneity was found by dwelling type or sex. Results were consistent across sensitivity analyses.

Mouldy area size was associated with current asthma and asthma symptom score, even for small sizes, adding new insight of the associations between mould contamination and asthma in adults.