Poverty-associated risk factors for wheezing in the first year of life in Honduras and El Salvador

Abstract

Background

Risk factors for wheezing specifically during the first year of life have been studied in well-developed countries, but the information from developing countries is very scarce. There are no such studies focusing on factors derived from poverty. The aim of the present study was to determine if risk factors related to poverty are associated to wheezing during the first year of life in infants from Honduras and El Salvador.

Methods

A survey, using a validated questionnaire, was carried out in the metropolitan area of San Pedro Sula (Honduras) and in La Libertad (El Salvador) in centres where infants attended for a scheduled vaccination shot or a healthy child visit at 12 months of age. Fieldworkers offered questionnaires to parents and helped the illiterate when necessary. The main outcome variable was wheezing during the first year of life, as reported by parents.

Results

A total of 1047 infants in El Salvador and 780 in Honduras were included in the analysis. The prevalence of wheeze in the first year was higher in El Salvador (41.2%) than in Honduras (27.7%), as was recurrent wheezing defined as three or more episodes (18.4% vs. 11.7%). Wheezing and recurrent wheezing was associated to unpaved floor in the household (summary odds ratios for both countries 1.55, p=0.036 and 1.72, p=0.054 for any wheeze and recurrent wheezing, respectively); dust entering from streets (1.30, p=0.052 and 1.67, p=0.008); living in a heavily polluted area (1.33, p=0.037 and 1.52, p=0.033); and having mould stains on the household walls (1.36, p=0.072 and 1.76, p=0.007). Furthermore, marginal associations were found for additional person at home and use of kerosene as cooking fuel. University studies in the mother (0.34, p=0.046 and 0.32, p=0.022) and a professional occupation in the father (0.34, p=0.046 and 0.26, p=0.047) were associated to a lower risk.

Conclusions

The prevalence of wheezing and recurrent wheezing is notoriously high in El Salvador and Honduras. In those populations factors related to poverty are associated to a higher prevalence of wheezing and recurrent wheezing, whereas higher maternal education and paternal professional occupation behave as protective factors.

Introduction

Although risk factors for wheezing during infancy and preschool age have been extensively studied in developed countries, there is much less information about those risk factors when wheezing is restricted just to the first year of life. Furthermore, the information from low-resourced countries is almost inexistent.¹

One of the earliest results on those risk factors during the first year of life was reported by Bisgaard et al.² who found that poor social environment, a smoking mother, day-care attendance, male gender, being born in April through September (in Denmark) and preterm birth were all independent risk factors for wheezing. Day-care attendance has been pointed out as a very important risk factor in subsequent studies.3, 4, 5 Parental history of asthma -sometimes only maternal ⁶ if wheeze persistency was considered- has also been found to be associated to early infant wheezing in several studies, which have focused their attention on the first year of life6, 7. Parental smoking has also been consistently associated to wheezing during the first year of life 5, 6, and smoking during pregnancy seems to be a risk factor independently of the mother smoking after delivery.8, 9, 10 In fact, smoking in pregnancy is related to a poor lung function in the infant at one month of age.¹¹

The prevalence of first year wheeze decreased to half after a heavily pollutant factory was closed in Calarasi (Romania).¹² Dampness at home has also been found to be a risk factor for early wheeze ¹³ independently of house dust mites growing. Recently, antibiotics consumption by the mother during pregnancy ¹⁴, rotavirus infection during the first year ¹⁵, and Chlamydia pneumoniae infection at 4 years ¹⁶ have also been significantly associated to wheezing during the first months of life. Furthermore, high mass index in the newborn is associated with reduced neonatal lung function¹¹.

The aforementioned studies have been carried out in affluent countries. However, two of them have pointed out that poor economic conditions and young maternal age (which is more frequent in non-affluent countries) may be risk factors for early wheezing.2, 6 Thus, we were interested in studying situations derived from poverty, which can be found more easily in non-affluent countries, and how they could be associated to the prevalence of wheeze. Therefore, we conducted a survey in a population-based cohort of one-year-old infants in San Pedro Sula (Honduras) and La Libertad (El Salvador), which are both non-affluent countries with similar genetic and environmental backgrounds.