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Title: Effects of household indoor air quality and environment on respiratory health of Maltese families
Authors: Bilocca, David (2020)
Keywords: Asthma -- Malta
Dermatophagoides pteronyssinus -- Malta
Allergy -- Malta
Asthma in children -- Malta
Hay fever in children -- Malta
Indoor air pollution -- Malta
Allergens -- Malta
Issue Date: 2020
Citation: Bilocca, D. (2020). Effects of household indoor air quality and environment on respiratory health of Maltese families (Doctoral dissertation).
Abstract: There is no doubt that the prevalence of asthma has been increasing worldwide with westernised countries faring worse than less developed ones. The ISAAC study in Malta, which was the largest local epidemiological study on asthma and allergies in childhood, has already established a high prevalence of asthma in Maltese children, with 27.2% reporting wheezing sometime in their life. It also revealed an extremely high prevalence of allergic rhinitis with Maltese adolescents (13–14-year olds) ranking as having the second highest prevalence worldwide. This study recruited children who participated in the Respira project, were adolescents (12-15- year olds), were studied in a case control design. Sixty-six cases were children who exhibited symptoms of uncontrolled asthma (namely wheezing in the past 12 months, exercise induced wheeze and nocturnal cough in the absence of a cold). The sixty-three controls were children who never had any symptoms suggestive of asthma, and who never had any manifestations of other allergic conditions. These children were equally distributed throughout the northern, central and southern areas of the island. These children together with their fathers and mothers underwent spirometry, exhaled nitric oxide testing, skin prick testing, acoustic rhinometry. Their houses were visited, and dust was collected for the presence of allergens and endotoxin. Adolescents who had uncontrolled asthma symptoms were found to have a higher lifetime exposure to tobacco smoke. 30.3% of cases were exposed to second-hand smoking (SHS) in their first year of life, while 40.9% had some current exposure to tobacco smoke. This contrasted to what was reported in the control group, where only 6.6% were exposed to SHS in the first-year old life, and 18.3% had current exposure in this group. Familial allergic conditions were extremely important factors in predicting whether a child was likely to be included in the uncontrolled asthmatic group. Having a sibling who had a history of asthma, was the strongest of these predictors, with an Odds Ratio of 6.1. This was followed by a father who had a history of asthma (OR 5.338) and/or a mother who had a history of nasal allergies (OR 3.038). Hence, one can observe the importance of a genetic predisposition, but also remember that these relatives would usually share the same dwelling and subsequently the same indoor environment which could lead to factors which could precipitate allergic conditions. Adolescents who had uncontrolled respiratory symptoms tended to live closer to roads with busy traffic (48.8% lived within 50m of such a road) when compared to children who had no symptoms (27.8%, p = 0.049). 36.5% of cases were reported be living in a house which had a noticeable smell of mould, while only 8.5% of the controls lived in a household with such a smell (p < 0.001). Also, there were more visible signs of mould in the bedrooms of case children (25%) when compared to control children (9.8%, p = 0.034). These conditions point to humid indoor environments, possibly promoting fungal growth and the presence of spores, which could have been triggering allergic conditions. Clinical testing in children confirmed that the most likely cause of uncontrolled symptoms in the case group was of an allergic aetiology, as in this group both FeNO (p <0.001) and serum total IgE (p = 0.027) was much higher when compared to the control group. Also, nasal patency by acoustic rhinometry revealed that in the left nostrils were smaller in the case group when compared to the control group (p = 0.011). The children who participated in this study were mostly atopic to house dust mite, followed by cat dander and olive tree pollen, with asthmatic adolescents being more likely to be atopic to house dust mite when compared to control children. Fathers who participated in this study were mostly atopic to house dust mite, followed by Parietaria pollen and grass mix pollen. Mothers were also mostly atopic to house dust mite, followed by Parietaria pollen but in contradistinction to fathers, the third most common aeroallergen they were atopic to was olive tree pollen. Case children were more likely to have a higher total serum IgE level in autumn when compared to spring (p = 0.015), while their fathers and mothers also had higher total mean serum IgE level in autumn when compared to spring (p = 0.006, p = 0.009). While there was no significant seasonal serum total IgE variability for doctor-diagnosed asthmatic fathers, doctor-diagnosed asthmatic mothers had a significantly higher mean serum total IgE level in winter when compared to autumn (p = 0.036). We also identified groups of individuals in both children and parents who were characterised by extremely high total IgE levels and higher airway inflammation, as evidenced by higher FeNO levels, and lower FEV1 and FEV1/FVC. Case children and parents who were classified in these groups were also more likely to have a higher serum specific HDM IgE level. Mean endotoxin levels were higher in houses in which mould growth had been reported, and in which mould growth was reported in the child’s bedroom (p = 0.024, p = 0.011). While there were no significant differences in the dust allergen levels collected from the houses of case and control children, mean HDM allergen levels in houses of case children who had a very high IgE level and high FeNO had higher HDM levels were detected in the house dust (p = 0.017). These findings were reproduced when the data from these adolescents were analysed together with the corresponding adolescents who participated in the same project, and who lived in Sicily, confirming higher mean house HDM allergen in the houses with the adolescent phenotype having a serum high total IgE (p = 0.007), and a strong correlation between these children’s specific HDM IgE and the presence of this allergen in the house dust (p = 0.019). This study confirmed that HDM as an indoor allergen in Maltese houses was a strong predictor for asthma in Maltese adolescents. It also identified phenotypes of both adolescents and adults being affected to a greater extent by this allergen. On the other hand, this study did not explain why the more common case phenotype who had lower serum IgE levels and airway inflammation had uncontrolled symptoms. Certain home characteristics such as houses which were located closer to busy roads and having the presence of indoor mould increased the likelihood of a child having asthma. Perhaps, further studies designed around first identifying phenotypes and then focusing on how various indoor environmental factors affect the particular phenotype of interest could be the answer to identifying which indoor environmental factors are instigating the expression of a particular asthma phenotype.
Description: PH.D.
Appears in Collections:Dissertations - FacM&S - 2020

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