Patterns of allergic sensitization and factors associated with emergence of sensitization in the rural tropics early in the life course: findings of an Ecuadorian birth cohort

Philip J Cooper; Irina Chis Ster; Martha E Chico; Maritza Vaca; Mauricio L Barreto; David P Strachan

doi:10.3389/falgy.2021.687073

Patterns of allergic sensitization and factors associated with emergence of sensitization in the rural tropics early in the life course: findings of an Ecuadorian birth cohort

Front Allergy. 2021 Aug 5:2:687073. doi: 10.3389/falgy.2021.687073.

Authors

Philip J Cooper^{1

2

3}, Irina Chis Ster¹, Martha E Chico³, Maritza Vaca³, Mauricio L Barreto^#⁴, David P Strachan^#⁵

Affiliations

¹ Institute of Infection and Immunity, St George's University of London, London, UK.
² Escuela de Medicina, Universidad Internacional del Ecuador, Quito, Ecuador.
³ Fundacion Ecuatoriana Para Investigacion en Salud, Quito, Ecuador.
⁴ Center for Data and Knowledge Integration for Health (CIDACS)-FIOCRUZ, Salvador, Brazil.
⁵ Population Health Research Institute, St George's University of London, London, UK.

^# Contributed equally.

Abstract

Introduction: There are limited data on emergence of allergic sensitization (or atopy) during childhood in tropical regions.

Methods: We followed a birth cohort of 2404 newborns to 8 years in tropical Ecuador and collected: risk factor data by maternal questionnaires periodically from birth; atopy was measured by skin prick test reactivity (SPT) to aeroallergens in parents, and aeroallergens and food allergens in children at 2, 3, 5, and 8 years; and stool samples for soil-transmitted helminths (STH) from children periodically to 8 years and from parents and household members at the time of recruitment of cohort children. Data on risk factors were measured either at birth or repeatedly (time-varying) from birth to 8 years. Longitudinal repeated-measures analyses were done using generalized estimating equations to estimate an the age-dependent risk of positive SPT (SPT+) to any allergen or mite during early childhood to school age.

Results: SPT+ to any allergen was present in 29.0% of fathers and 24.8% of mothers, and in cohort children increased with age, initially to mite but later to cockroach, reaching 14.8% to any allergen (10.7% mite and 5.3% cockroach) at 8 years. Maternal SPT+, particularly presence of polysensitization (OR 2.04, 95% CI 1.49-2.77) significantly increased the risk of SPT+ during childhood, while household overcrowding at birth decreased the risk (OR 0.84, 95% CI 0.72-0.98). For mite sensitization, maternal polysensitization increased (OR 2.14, 95% CI 1.40-3.27) but rural residence (OR 0.69, 95% CI 0.50-0.94) and birth order (3^rd -4^th vs. 1^st - 2^nd: OR 0.71, 95% CI 0.52-0.98) decreased the risk. Time-varying exposures to agricultural activities (OR 0.77, 95% CI 0.60-0.98) and STH parasites (OR 0.70, 95% CI 0.64-0.91) during childhood decreased while anthelmintics increased the childhood risk (OR 1.47, 95% CI 1.05-2.05) of mite sensitization.

Conclusion: Our data showed the emergence of allergic sensitization, primarily to mite and cockroach allergens, during childhood in tropical Ecuador. A role for both antenatal and postnatal factors acting as potential determinants of SPT+ emergence was observed.

Keywords: allergic sensitization; atopy; childhood; cohort; risk factors; tropics.

Abstract

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