Original Articles: Asthma, Lower Airway DiseasesRisk factors for wheezing in early adolescence: a prospective birth cohort study in Brazil
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)
- 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) - et al.
Current estimates from the National Health Interview Survey, 1994
Vital Health Stat 10
(1995) - et al.
Trends in prevalence and severity of childhood asthma
BMJ
(1994) - et al.
Surveillance for asthma—United States, 1980-1999
MMWR Surveill Summ
(2002) - et al.
Surveillance for asthma—United States, 1960-1995
MMWR CDC Surveill Summ
(1998) Asthma in the United States: burden and current theories
Environ Health Perspect
(2002)- et al.
Invited commentary: obesity and asthma: new perspectives, research needs, and implications for control programs
Am J Epidemiol
(2002) - et al.
Do risk factors for childhood infections and malnutrition protect against asthma? a study of Brazilian male adolescents
Am J Public Health
(2003)
Cited by (0)
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).