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Very low birthweight and asthma by age seven years in a national cohort
B A Darlow1, L J Horwood, N Mogridge
1Department of Paediatrics, Christchurch School of Medicine, Christchurch, New Zealand. brian.darlow@chmeds.ac.nz
Insights
Childhood asthma is common in very low birthweight (VLBW) infants, with 50% diagnosed before age 7. Asthma risk appears linked to social factors like maternal smoking, not perinatal issues.
Area of Science:
- Pediatrics
- Respiratory Medicine
- Epidemiology
Background:
- Very low birthweight (VLBW) is linked to increased respiratory issues in childhood.
- Chronic lung disease in VLBW infants may further elevate asthma risk.
Purpose of the Study:
- To determine asthma prevalence at 7-8 years in a national cohort of VLBW infants born in 1986.
- To investigate associations between asthma and perinatal factors, and social/familial factors.
Main Methods:
- A national cohort of 299 VLBW children (born 1986) in New Zealand was assessed.
- Parental questionnaires collected data on asthma diagnosis, current asthma, and daily medication use.
- Statistical analysis, including logistic regression, examined predictors of asthma.
Main Results:
- 50% of VLBW children were diagnosed with asthma before age 7; 32% had asthma at age 7.
- Asthma diagnosis was associated with maternal smoking during pregnancy and current maternal smoking.
- Family history of asthma predicted all asthma outcomes; social factors influenced treatment.
Conclusions:
- Childhood asthma rates are high in VLBW cohorts.
- Asthma prevalence in this VLBW cohort is not associated with perinatal factors.
- Social determinants, including maternal smoking and ethnicity, appear to influence asthma risk and treatment in VLBW children.
Abstract:
Several studies have suggested that very low birthweight (VLBW < 1500 g) is associated with increased rates of respiratory problems in childhood and that the presence of chronic lung disease further increases the risk. We aimed to assess rates of asthma at 7-8 years of age in a national cohort of VLBW infants born in 1986 and for whom perinatal data were available. Two hundred ninety-nine former VLBW children (96% of surviving children living in New Zealand) were assessed at a home visit. Parents were asked a comprehensive questionnaire, including three questions aimed at assessing morbidity from asthma: 1) was the child diagnosed as having asthma before age 7 years; 2) was the child still experiencing asthma at the age of 7 years; and 3) was the child prescribed daily medication for asthma at the age of 7 years. Overall, 50% of the cohort had been diagnosed with asthma before age 7, compared with 27% of a sample of New Zealand children assessed contemporaneously in an international study; 32% had asthma at age 7, and 11% were taking daily medication. All three categories of asthma were associated with a family history of asthma, but there was no association with any perinatal factors. A diagnosis of asthma before age 7 was more likely when the mother smoked in pregnancy (P < 0.005) and currently smoked (P < 0.01), and trended so when parents lacked high school qualifications and in Maori or Pacific Island families (P < 0.10). In contrast, daily medication was more frequent when parents had educational qualifications and in non-Maori or Pacific Island families (P < 0.05). On multiple logistic regression, a family history of asthma was a significant predictor for any and current asthma (P < 0.001) and daily medication (P < 0.05); maternal smoking in pregnancy was a significant predictor for any asthma (P < 0.05); and non-Maori or Pacific Island ethnicity was a significant predictor for asthma treatment (P < 0.05). We conclude that rates of childhood asthma are high in this VLBW cohort, but the high prevalence appears to be unrelated to perinatal factors, including respiratory morbidity. There are suggestions that social factors contribute to both asthma risk and treatment.