Hygiene hypothesis: association between hygiene and asthma among preschool children in Lebanon

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Souheil Hallit
Hala Sacre
Nelly Kheir
Eva Hobeika
Rabih Hallit
Mirna Waked
Pascale Salameh


hygiene, hypothesis, asthma, pre-school, children.


Objectives: To validate a scale to assess the hygiene hypothesis and the association between hygiene and asthma among Lebanese preschool children aged 3–5 years.

Methods: This cross-sectional study, conducted between November 2018 and March 2019, enrolled 515 preschool children. Asthma and potential risk factors, including hygiene, were assessed using a standardized questionnaire. A specific hygiene hypothesis scale has been generated and validated for this purpose.

Results: The hygiene hypothesis scale items converged over a solution of nine factors that had an Eigenvalue over 1, explaining a total of 65.86% of the variance. An acceptable Cronbach’s alpha value was recorded for the hygiene hypothesis scale (0.696). Variables correlated with higher odds of asthma were male gender (ORa = 0.41 for females), living near a prairie sprayed with pesticides (ORa = 3.09), having a heating system in the bedroom compared to the sitting room (ORa = 9.97), attending kindergarten (ORa = 2.80), having a mother who smokes waterpipe compared to not smoking (ORa = 3.34), having a mother with a history of asthma (ORa = 5.50), and having respiratory infections (ORa = 14.72). However, the hygiene hypothesis score was not associated with higher odds of asthma (p = 0.881).

Conclusions: The current results suggested that neither home cleaning nor personal cleanliness was correlated with asthma in preschool children. Larger prospective studies that measure the intensity and duration of exposure to each toxicant are suggested to better assess the hygiene hypothesis items and their association with asthma.

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