Gender differences in the relationship between body mass index (BMI) changes and the prevalence and severity of wheezing and asthma in the first year of life

Abstract

Background

Rapid weight gain has been recently associated with asthma at school age, but its influence in respiratory symptoms during infancy is still unknown.

Methods

Answers from 6541 parents living in six different cities of Brazil to the International Study of Wheezing in Infants (EISL) questionnaire were analysed. Data from reported weight and height at birth and at one year were used to calculate BMI. Rapid body mass index (BMI) gain was defined by the difference in BMI superior to 1.0z and excessive by the difference superior to 2.0z.

Results

Rapid BMI gain was found in 45.8% infants and excessive in 24.4%. Boys showed a significantly higher BMI gain than girls. Girls with rapid BMI gain showed a significantly higher prevalence of hospitalisation for wheezing (8.8% vs. 6.4%; aOR: 1.4, 95%CI: 1.1–1.8), severe wheezing (18.1% vs. 15.0%; aOR: 1.3, 95%CI: 1.0–1.5) and medical diagnosis of asthma (7.5% vs. 5.7%; aOR: 1.3, 95%CI: 1.0–1.7). Girls with excessive BMI gain also had a significantly higher prevalence of hospitalisation for wheezing (9.8% vs. 6.7%; aOR: 1.5, 95%CI: 1.1–2.0) and severe wheezing (18.9% vs. 15.5%; aOR: 1.3, 95%CI: 1.0–1.6). No significant association was found among boys.

Conclusions

The majority of the evaluated infants showed BMI gain above expected in the first year of life. Although more commonly found in boys, rapid and excessive BMI gain in the first year of life was significantly related to more severe patterns of wheezing in infancy among girls.

Introduction

Respiratory diseases are a significant health problem among infants and are responsible for high morbidity and mortality, and also for a large number of unscheduled medical visits and hospitalisations.¹ Prospective cohort studies have shown that the majority of wheezing infants have transient symptoms unrelated to asthma.2, 3 Infants with severe or recurrent wheezing, however, do not rarely grow up with persistent symptoms and pulmonary impairment.⁴

According to the ISAAC (International Study of Asthma and Allergies in Childhood) study, asthma is a highly prevalent disease in Brazil, affecting almost a quarter of school-aged children and 20% of adolescents.⁵ Despite the challenges in establishing a reliable diagnosis, asthma must be considered as one of the leading diagnosis possibilities in infants with recurrent wheezing. It has been estimated that over a third of asthmatics are already symptomatic in the first year of life and that early manifestations are a marker of asthma severity.⁶

The study EISL (Estudio Internacional de Sibilancias en Lactantes) evaluated the epidemiological profile of wheezing and asthma among infants in several centres in Latin America and Europe employing a validated and standardised instrument.1, 7, 8 The Brazilian data from this study were obtained from seven state capitals evaluating data from almost 13,000 infants and clearly show the huge impact of wheezing among local infants. Approximately 50% of the surveyed infants had at least one episode of wheezing in the first year of life, over 25% had recurrent wheezing, and 10% had been already diagnosed as asthmatic.¹

Several risk factors have been described for recurrent wheezing and asthma in infants, such as male gender, positive family history of asthma, atopic dermatitis and maternal smoking during pregnancy, whereas breastfeeding is one of the few protective factors.⁹ Rapid weight gain has been recently associated with a higher incidence of wheezing, asthma, and respiratory symptoms in preschool and school-aged children.10, 11, 12, 13, 14 This association has not been fully studied for respiratory outcomes in the first years of life.

Asthma and wheezing tend to have different characteristics between genders. Male gender is classically associated with a higher incidence and severity of wheezing and asthma in infancy and childhood and this pattern changes after puberty, when women have a higher incidence of asthma.¹⁵ Female gender is also associated with a specific phenotype of severe asthma in adults, mainly non-atopic and related to obesity.16, 17

The purpose of this study was to evaluate possible associations and sex differences between body mass index (BMI) changes in the first year of life with the prevalence and severity of wheezing and asthma among infants from six Brazilian state capitals who participated in the EISL study.