Association between agent orange and birth defects: systematic review and meta-analysis

Ngo, Anh D., Taylor, Richard, Roberts, Christine L. and Nguyen, Tuan V. (2006) Association between agent orange and birth defects: systematic review and meta-analysis. International Journal of Epidemiology, 35 5: 1220-1230.


Author Ngo, Anh D.
Taylor, Richard
Roberts, Christine L.
Nguyen, Tuan V.
Title Association between agent orange and birth defects: systematic review and meta-analysis
Journal name International Journal of Epidemiology   Check publisher's open access policy
ISSN 1464-3685
0300-5771
Publication date 2006-10-01
Sub-type Article (original research)
DOI 10.1093/ije/dyl038
Volume 35
Issue 5
Start page 1220
End page 1230
Total pages 11
Editor G. Davey Smith
S. Ebrahim
Place of publication Oxford
Publisher Oxford University Press
Collection year 2006
Language eng
Subject 320000 Medical and Health Sciences
C1
321005 Fetal Development and Medicine
730306 Evaluation of health outcomes
Formatted abstract Background
The association between parental exposure to Agent Orange or dioxin and birth defects is controversial, due to inconsistent findings in the literature. The principal aim of this study was to conduct a meta-analysis of relevant epidemiological studies that examined this association and to assess the heterogeneity among studies.

Methods
Relevant studies were identified through a computerized literature search of Medline and Embase from 1966 to 2002; reviewing the reference list of retrieved articles and conference proceedings; and contacting researchers for unpublished studies. A specified protocol was followed to extract data on study details and outcomes. Both fixed-effects and random-effects models were used to synthesize the results of individual studies. The Cochrane Q test and index of heterogeneity (I-2) were used to evaluate heterogeneity, and a funnel plot and Egger's test were used to evaluate publication bias.

Results
In total, 22 studies including 13 Vietnamese and nine non-Vietnamese studies were identified. The summary relative risk (RR) of birth defects associated with exposure to Agent Orange was 1.95 [95% confidence interval (95% CI) 1.59-2.39], with substantial heterogeneity across studies. Vietnamese studies showed a higher summary RR (RR = 3.00; 95% CI 2.19-4.12) than non-Vietnamese studies (RR = 1.29; 95% CI 1.04-1.59). Sub-group analyses found that the magnitude of association tended to increase with greater degrees of exposure to Agent Orange, rated on intensity and duration of exposure and dioxin concentrations measured in affected populations.

Conclusion

Parental exposure to Agent Orange appears to be associated with an increased risk of birth defects.
Keyword Agent Orange
dioxin
birth defects
meta-analysis
Vietnam
Public, Environmental & Occupational Health
Corps Vietnam Veterans
Adipose-tissue
Postservice Mortality
Reproductive Outcomes
Dioxin Contamination
Pregnancy Outcomes
Era Veterans
Follow-up
2,3,7,8-tetrachlorodibenzo-p-dioxin
Dibenzofurans
Q-Index Code C1

 
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