Premature Birth and Asthma Among Young Puerto Rican Children

Asthma in US Mexican-Origin Children in Early Childhood: Differences in Risk and Protective Factors by Parental Nativity

OBJECTIVE

Over 900,000 Mexican-origin children in the United States have asthma, but little is known about the extent to which development of this condition reflects early childhood exposure to social and environmental risks. The objectives of this research are to demonstrate the roles of risk and protective factors in the prevalence and severity of asthma in this population and provide comparisons with other racial/ethnic groups.

METHODS

Nationally representative data from the Early Childhood Longitudinal Study, Birth Cohort (n = 6900), with county-level ozone data appended to this file were analyzed using descriptive and multivariate regression methods.

RESULTS

The odds of asthma diagnosis by 60 months are approximately 50% higher among Mexican-origin children than for non-Hispanic whites (P < .05) in multivariate analyses. Compared to those with foreign-born parents, Mexican-origin children with native-born parents have a lower likelihood of being breast-fed and greater chances of having risks including a family history of asthma, having respiratory illnesses and allergies, living with a smoker, and attending center-based child care. Mexican-origin children live in counties with over 3 times more elevated ozone days annually than non-Hispanic whites.

CONCLUSIONS

Mexican-origin children experience a constellation of risk and protective factors, but those with US-born parents have elevated asthma risks compared to those with foreign-born parents. Asthma incidence and severity will likely increase as this population becomes increasingly integrated into US society.

Preterm birth and childhood wheezing disorders: a systematic review and meta-analysis

BACKGROUND

Accumulating evidence implicates early life factors in the aetiology of non-communicable diseases, including asthma/wheezing disorders. We undertook a systematic review investigating risks of asthma/wheezing disorders in children born preterm, including the increasing numbers who, as a result of advances in neonatal care, now survive very preterm birth.

METHODS AND FINDINGS

Two reviewers independently searched seven online databases for contemporaneous (1 January 1995-23 September 2013) epidemiological studies investigating the association between preterm birth and asthma/wheezing disorders. Additional studies were identified through reference and citation searches, and contacting international experts. Quality appraisal was undertaken using the Effective Public Health Practice Project instrument. We pooled unadjusted and adjusted effect estimates using random-effects meta-analysis, investigated "dose-response" associations, and undertook subgroup, sensitivity, and meta-regression analyses to assess the robustness of associations. We identified 42 eligible studies from six continents. Twelve were excluded for population overlap, leaving 30 unique studies involving 1,543,639 children. Preterm birth was associated with an increased risk of wheezing disorders in unadjusted (13.7% versus 8.3%; odds ratio [OR] 1.71, 95% CI 1.57-1.87; 26 studies including 1,500,916 children) and adjusted analyses (OR 1.46, 95% CI 1.29-1.65; 17 studies including 874,710 children). The risk was particularly high among children born very preterm (<32 wk gestation; unadjusted: OR 3.00, 95% CI 2.61-3.44; adjusted: OR 2.81, 95% CI 2.55-3.12). Findings were most pronounced for studies with low risk of bias and were consistent across sensitivity analyses. The estimated population-attributable risk of preterm birth for childhood wheezing disorders was ≥3.1%. Key limitations related to the paucity of data from low- and middle-income countries, and risk of residual confounding.

CONCLUSIONS

There is compelling evidence that preterm birth-particularly very preterm birth-increases the risk of asthma. Given the projected global increases in children surviving preterm births, research now needs to focus on understanding underlying mechanisms, and then to translate these insights into the development of preventive interventions.

REVIEW REGISTRATION

PROSPERO CRD42013004965.