Original Articles: Asthma, Lower Airway Diseases
Risk factors for wheezing in early adolescence: a prospective birth cohort study in Brazil

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Background

Many asthma studies are available in the literature, but few investigated whether risk factors for asthma differ by sex.

Objective

To evaluate risk factors for wheezing in early adolescence, with emphasis on sex differences.

Methods

A prospective birth cohort study was initiated in 1993; 87.5% of the original cohort was traced at 11 years, totaling 4,452 adolescents. Current wheezing was defined as at least 1 crisis in the previous 12 months. The following independent variables were analyzed: maternal smoking during pregnancy, wheezing at 4 years, maternal wheezing, and adolescent body mass index.

Results

Current wheezing affected 13.5% (95% confidence interval [CI], 12.4%-14.5%) of the cohort. The prevalence of current wheezing was 15.3% (95% CI, 13.7%-16.8%) in boys and 11.7% (95% CI, 10.4%-13.1%) in girls (P < .001). Maternal smoking was related to an increased risk of wheezing for boys but not for girls. There was a significant tracking of wheezing from 4 to 11 years in both sexes, although the magnitude was stronger for boys. A dose-response association between maternal wheezing and adolescent wheezing was observed in boys but not in girls. Finally, obesity was associated with an increased risk of wheezing in boys but not in girls.

Conclusions

The variables explored in this investigation had a stronger effect on adolescent wheezing in boys than in girls. Public health strategies aimed at minimizing the burden of wheezing should take these sex differences into account.

Section snippets

INTRODUCTION

Asthma is the most prevalent chronic disease in childhood and also affects a substantial proportion of adolescents, 1 and there is some evidence that its prevalence is rising. 2, 3, 4 The presence of asthma increases the risk of mortality. 3, 4 A combination of environmental and lifestyle factors seems to be responsible for the increase in asthma estimates. 5, 6 Obtaining a precise estimate of the prevalence of asthma is challenging for public health researchers, and studies that focus on

METHODS

Pelotas is a medium-sized Brazilian city located near to the southern border of the country. In 1993, all hospital births (>99% of all city births) were monitored, and the mothers were invited to join a birth cohort study. Mothers who agreed to take part in the study answered a standardized and pretested questionnaire soon after delivery. The questionnaire included questions on maternal smoking during each trimester of pregnancy (yes/no). For this analysis, a variable categorized only as smoker

RESULTS

The 1993 Pelotas (Brazil) birth cohort includes 5,249 individuals born in 1993 in the city of Pelotas. Only 16 children born in 1993 were not included in the cohort study, which represents a response rate of 99.7%. At 4 years, 1,273 children were included in a follow-up visit, representing 87.2% of those sampled for this visit. At 11 years, 87.5% of all cohort members were interviewed.

Of 4,425 participants with complete data on wheezing patterns in the 2004-2005 visit, 1,935 (43.7%) reported

DISCUSSION

In accordance with the original hypothesis of this investigation, we found that risk factors for wheezing in early adolescence were different for boys and girls. In summary, the independent variables studied had a greater effect on wheezing in boys than in girls. Other researchers have investigated the role of sex differences in the development of asthma. In a New Zealand birth cohort study, Mandhane and coworkers 9 showed that boys were more likely to develop asthma in childhood and that girls

REFERENCES (16)

  • A Must et al.

    Reference data for obesity: 85th and 95th percentiles of body mass index (wt/ht2) and triceps skinfold thickness

    Am J Clin Nutr

    (1991)
  • PF Adams et al.

    Current estimates from the National Health Interview Survey, 1994

    Vital Health Stat 10

    (1995)
  • HR Anderson et al.

    Trends in prevalence and severity of childhood asthma

    BMJ

    (1994)
  • DM Mannino et al.

    Surveillance for asthma—United States, 1980-1999

    MMWR Surveill Summ

    (2002)
  • DM Mannino et al.

    Surveillance for asthma—United States, 1960-1995

    MMWR CDC Surveill Summ

    (1998)
  • SC Redd

    Asthma in the United States: burden and current theories

    Environ Health Perspect

    (2002)
  • SC Redd et al.

    Invited commentary: obesity and asthma: new perspectives, research needs, and implications for control programs

    Am J Epidemiol

    (2002)
  • R da Costa Lima et al.

    Do risk factors for childhood infections and malnutrition protect against asthma? a study of Brazilian male adolescents

    Am J Public Health

    (2003)
There are more references available in the full text version of this article.

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This analysis was supported by the Wellcome Trust's initiative entitled Major Awards for Latin America on Health Consequences of Population Change. Earlier phases of the 1993 cohort study were funded by the European Union, the National Program for Centers of Excellence (Brazil), the National Research Council (Brazil), and the Ministry of Health (Brazil).

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