WHAT IS ALREADY KNOWN ON THIS TOPIC

Household damp is a major public health challenge with 1.6 million children in England estimated to be living in affected properties.

Damp exposure in early childhood is associated with increased respiratory symptoms and subsequent diagnosis of asthma.

WHAT THIS STUDY ADDS

Visible damp in a child’s bedroom but not elsewhere in the household is associated with primary care attendance for cough and wheeze as well as inhaled steroid and reliever inhaler prescription.

The location of damp within the household may be an important determinant of the impact of mould on children’s respiratory health.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

Health professionals should enquire about both the presence and location of household damp in children presenting with recurrent respiratory symptoms.

The presence of visible damp in a child’s bedroom could be used to help identify those families most urgently in need of targeted household damp treatment by the local government.

Introduction

The burden of preschool wheeze and cough is a prominent public health issue that appears to be increasing in prevalence and is associated with significant morbidity, healthcare utilisation and cost.1 The aetiology of preschool wheeze and cough, and childhood asthma is a complex interplay between host genetics and environmental factors that may be modifiable.2

There is compelling evidence from a series of meta-analyses and systematic reviews that early life exposure to household damp is associated with respiratory symptoms and subsequent diagnosis of asthma.3 4 There has been a renewed focus on the harmful impact of damp in the UK after the tragic death of Awaab Ishak in 2020 following mould inhalation from extensive damp in the family’s home. Awaab’s law was introduced as part of the Social Housing (Regulation) Act 2023 and requires social housing landlords in England to investigate and treat damp issues.

Household damp is a substantial public health problem with an estimated 1.6 million children in England living in affected properties.5 Tackling this potentially preventable cause of significant respiratory morbidity in children is vitally important and identifying which household rooms affected by damp are most associated with respiratory outcomes could allow remediation work to be efficiently targeted. The aim of our study was to assess the impact of the location of household visible damp on respiratory symptoms, infections, healthcare utilisation and medication prescription for wheezing during the first 2 years of life.

Methods

Pregnant women were recruited to the GO-CHILD prospective birth cohort study between August 2009 and November 2013 from throughout England and Scotland to investigate the role of environmental and gene variation on respiratory outcomes in young children. Postal questionnaires were completed at 12 and 24 months to determine household damp exposure and respiratory symptoms and outcomes (see online supplemental file 1 for questionnaires). Carers provided informed consent.

Exposure and outcomes

Carers were asked whether there was visible damp within the house and whether damp was present in the bathroom, kitchen, living room or the child’s bedroom. The frequency of respiratory symptoms (wheeze and cough), healthcare utilisation (primary care attendance, emergency department attendance and secondary care referral) and medication prescriptions (reliever inhaler, inhaled and oral corticosteroid) for wheeze were recorded. The frequency of respiratory infections (bronchiolitis, pneumonia, otitis media and cold or influenza) were also recorded.

Statistical analysis

Data on children whose carers had completed at least one follow-up questionnaire were included in the analysis. The data was reshaped into a long format to enable analysis of repeated measures. A cluster variance estimator adjustment was made to the SEs to take account of repeated measures. Log binomial regression was used for binary outcomes. Ordinal logistic regression was used for ordered grouped counts. A regression analysis was performed for each of the 12 clinical outcomes. On the basis of existing knowledge and following discussion with the GO-CHILD study team, models were adjusted for: the mother’s level of education; daycare attendance; breast feeding beyond 6 months; siblings at home; environmental tobacco smoke exposure; child’s bedroom flooring (as a surrogate of house dust mite); animal exposure; road traffic density (traffic pollution) around child’s home (little/moderate/dense); and solid fuel pollution within the home (see online supplemental file 2 for confounder analyses). A two-sided p value of <0.05 was deemed statistically significant for all analyses. Stata (StataCorp 2019 Stata Statistical Software: Release 16 College Station, Texas: StataCorp) was used for all statistical analyses. Our study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology principles6 for reporting cohort studies.

Results

Data were collected from August 2010 to January 2016. 1344 children were included in the analyses with at least 1 carer follow-up questionnaire completed (figure 1). Visible damp was present in over a quarter of homes (25.3%) and was most common in the living room (15.1%), bathroom (12.2%) and children’s bedroom (8.3%). Visible damp was present in the bedroom only in 10.9% of the 340 homes affected by damp. Demographic information, damp exposure, environmental factors and follow-up are summarised in table 1.

Table 1

Demographic information, damp exposure, environmental factors and follow-up

Damp in the child’s bedroom was associated with an increased risk of dry cough (adjusted relative risk (RR) 1.56, 95% CI 1.07 to 2.27; p=0.021) and increased odds of primary care attendance for cough and wheeze (adjusted OR 1.37, 95% CI 1.07 to 1.76; p=0.009) (table 2). It was also associated with an increased risk of reliever inhaler (adjusted RR 2.01, 95% CI 1.21 to 2.79; p=0.018) and a greater than twofold increased risk of inhaled corticosteroid (adjusted RR 2.22, 95% CI 1.04 to 4.74; p=0.038) prescription (table 2). There was no association between the presence of damp in the bathroom, kitchen or living room with any respiratory or infection-related outcomes (online supplemental file 3).

Table 2

Presence of damp in a child’s bedroom and the occurrence of respiratory symptoms, healthcare utilisation, medication prescriptions and respiratory infections

Discussion

Visible damp in the child’s bedroom was associated with an increased risk of cough and wheeze requiring primary care review as well as the requirement for a reliever and steroid controller inhaler prescription. The location of damp within the household may be an important determinant of the impact of mould on children’s respiratory health. The association with the child’s bedroom is logical as this is the location where the child is likely to spend the greatest period of time and thus have the greatest potential duration of mould exposure.

Visible damp anywhere within the house in the GO-CHILD birth cohort has been reported previously.7 It was associated with an increased risk of dry cough, and increased odds of wheeze as well as primary care attendance for cough and wheeze. There was also an increased risk of reliever inhaler and inhaled corticosteroid prescription (online supplemental file 2).

Damp surfaces provide conditions favourable for the indoor growth of mould. Penicillium spp, Cladosporium spp, Aspergillus spp and Alternaria spp are common mould allergens found in houses with visible damp.8 It is hypothesised that these microscopic allergens can induce inflammation by releasing mycotoxins and by antigen-specific (IgE) mast cell activation.8 A series of meta-analyses and systematic reviews provide robust evidence that early life exposure to visible damp is associated with early asthma symptoms and later diagnosis of asthma.3 4 Early life damp exposure may have a long-term impact on respiratory health with an adverse impact on lung function growth in young people between aged 12 and 16 years identified9 as well as an increased risk of asthma at age 16.10

The scale of the public health challenge of damp in UK housing is substantial with the regulator of Social Housing publishing a report in February 2023 estimating that up to 160 000 social homes in England (3–4%) were impacted by ‘notable’ damp and mould and an estimated 1.6 million children in England are living in affected properties.5

The government’s ambition to address household damp is clear with the introduction of Awaab’s law compelling landlords to address damp and mould in social homes. Citizen’s advice (www.citizensadvice.org.uk) and the charity Shelter (www.shelter.org.uk) provide comprehensive advice on dealing with damp and mould issues in private rented homes. Raising awareness among parents and health professionals of the health issues effecting children who live in damp environments is important. Our findings will be valuable in assisting health professionals in advocating for their vulnerable patients as well as helping local government prioritise action for families whose children’s bedrooms are affected by visible mould.

There are notable limitations that should be considered when assessing our study findings. Recall bias is an important consideration given the retrospective questionnaires used to determine symptoms, diagnoses and treatments. Misclassification bias is another potential limitation given diagnoses were carer-reported and not always confirmed by a physician. Carer focus group feedback was obtained to ensure questionnaire definitions were unambiguous and to limit misclassification error with only 1.4% of carers reporting difficulty in understanding the study questionnaires. Guidance to clarify the definition of damp was not included within the questionnaires representing another potential cause of misclassification bias. Future studies could address this by using trained inspectors to visit homes to classify and assess the extent of damp. Alternatively, detection and quantification of mould in indoor air and settled dust is possible using Mould Specific Quantitative PCR.11 This technology has been used to develop the Environmental Relative Moldiness Index (ERMI) scale which via dust sampling protocols can quantify the burden of mould within the home.12 Children with high ERMI exposure in the first year of life have been shown to have a significantly increased risk of developing asthma at 7 years of age.13

Correction for multiple comparisons was not undertaken to avoid inflating type II error so reducing the risk of missing potentially important true associations.14 15

Conclusion

Our study highlights the importance of identifying both the presence and location of household damp exposure in the history of a child presenting with recurrent respiratory symptoms. The presence of damp within a child’s bedroom should be considered as an eligibility criterion to prioritise households requiring urgent damp assessment and remedial intervention.

Data availability statement

Data are available upon reasonable request.

Ethics statementsPatient consent for publication

Not applicable.

Ethics approval

The study was approved by the Tayside Committee on Medical Research & Ethics (FB/08/S1401/130). Participants gave informed consent to participate in the study before taking part.