BACKGROUND: Accumulating evidence implicates early life factors in<br />the aetiology of non-communicable diseases, including asthma/wheezing<br />disorders. We undertook a systematic review investigating risks of<br />asthma/wheezing disorders in children born preterm, including the<br />increasing numbers who, as a result of advances in neonatal care,<br />now survive very preterm birth. METHODS AND FINDINGS: Two reviewers<br />independently searched seven online databases for contemporaneous<br />(1 January 1995-23 September 2013) epidemiological studies investigating<br />the association between preterm birth and asthma/wheezing disorders.<br />Additional studies were identified through reference and citation<br />searches, and contacting international experts. Quality appraisal<br />was undertaken using the Effective Public Health Practice Project<br />instrument. We pooled unadjusted and adjusted effect estimates using<br />random-effects meta-analysis, investigated "dose-response" associations,<br />and undertook subgroup, sensitivity, and meta-regression analyses<br />to assess the robustness of associations. We identified 42 eligible<br />studies from six continents. Twelve were excluded for population<br />overlap, leaving 30 unique studies involving 1,543,639 children.<br />Preterm birth was associated with an increased risk of wheezing disorders<br />in unadjusted (13.7% versus 8.3%; odds ratio [OR] 1.71, 95% CI 1.57-1.87;<br />26 studies including 1,500,916 children) and adjusted analyses (OR<br />1.46, 95% CI 1.29-1.65; 17 studies including 874,710 children). The<br />risk was particularly high among children born very preterm (<32<br />wk gestation; unadjusted: OR 3.00, 95% CI 2.61-3.44; adjusted: OR<br />2.81, 95% CI 2.55-3.12). Findings were most pronounced for studies<br />with low risk of bias and were consistent across sensitivity analyses.<br />The estimated population-attributable risk of preterm birth for childhood<br />wheezing disorders was >/=3.1%. Key limitations related to the paucity<br />of data from low- and middle-income countries, and risk of residual<br />confounding. CONCLUSIONS: There is compelling evidence that preterm<br />birth-particularly very preterm birth-increases the risk of asthma.<br />Given the projected global increases in children surviving preterm<br />births, research now needs to focus on understanding underlying mechanisms,<br />and then to translate these insights into the development of preventive<br />interventions. REVIEW REGISTRATION: PROSPERO CRD42013004965.
Mebrahtu, T. F., Feltbower, R. G., Greenwood, D. C., & Parslow, R. C. (2015). Birth weight and childhood wheezing disorders: A systematic review and meta-analysis. Journal of Epidemiology and Community Health, 69(5), 500–508. https://doi.org/10.1136/jech-2014-204783