Case-control study of IL13 polymorphisms, smoking, and rhinoconjunctivitis in Japanese women: the Kyushu Okinawa Maternal and Child Health Study

Active or passive exposure to tobacco smoking and allergic rhinitis, allergic dermatitis, and food allergy in adults and children: a systematic review and meta-analysis

BACKGROUND

Allergic rhinitis, allergic dermatitis, and food allergy are extremely common diseases, especially among children, and are frequently associated to each other and to asthma. Smoking is a potential risk factor for these conditions, but so far, results from individual studies have been conflicting. The objective of this study was to examine the evidence for an association between active smoking (AS) or passive exposure to secondhand smoke and allergic conditions.

METHODS AND FINDINGS

We retrieved studies published in any language up to June 30th, 2013 by systematically searching Medline, Embase, the five regional bibliographic databases of the World Health Organization, and ISI-Proceedings databases, by manually examining the references of the original articles and reviews retrieved, and by establishing personal contact with clinical researchers. We included cohort, case-control, and cross-sectional studies reporting odds ratio (OR) or relative risk (RR) estimates and confidence intervals of smoking and allergic conditions, first among the general population and then among children. We retrieved 97 studies on allergic rhinitis, 91 on allergic dermatitis, and eight on food allergy published in 139 different articles. When all studies were analyzed together (showing random effects model results and pooled ORs expressed as RR), allergic rhinitis was not associated with active smoking (pooled RR, 1.02 [95% CI 0.92-1.15]), but was associated with passive smoking (pooled RR 1.10 [95% CI 1.06-1.15]). Allergic dermatitis was associated with both active (pooled RR, 1.21 [95% CI 1.14-1.29]) and passive smoking (pooled RR, 1.07 [95% CI 1.03-1.12]). In children and adolescent, allergic rhinitis was associated with active (pooled RR, 1.40 (95% CI 1.24-1.59) and passive smoking (pooled RR, 1.09 [95% CI 1.04-1.14]). Allergic dermatitis was associated with active (pooled RR, 1.36 [95% CI 1.17-1.46]) and passive smoking (pooled RR, 1.06 [95% CI 1.01-1.11]). Food allergy was associated with SHS (1.43 [1.12-1.83]) when cohort studies only were examined, but not when all studies were combined. The findings are limited by the potential for confounding and bias given that most of the individual studies used a cross-sectional design. Furthermore, the studies showed a high degree of heterogeneity and the exposure and outcome measures were assessed by self-report, which may increase the potential for misclassification.

CONCLUSIONS

We observed very modest associations between smoking and some allergic diseases among adults. Among children and adolescents, both active and passive exposure to SHS were associated with a modest increased risk for allergic diseases, and passive smoking was associated with an increased risk for food allergy. Additional studies with detailed measurement of exposure and better case definition are needed to further explore the role of smoking in allergic diseases.

Association of interleukin-13 SNP rs20541 (Arg>Gln) to allergic rhinitis in an Asian population of ethnic Chinese in Singapore

In this study, we report our findings as we evaluated the association of IL-13 SNP rs20541 to AR as reported in the meta-analysis (Ying, X-J et al., April, Gene 2013) in an Asian population of 1322 ethnic Chinese recruited in Singapore well defined and characterized for allergic rhinitis. The SNP was significantly associated with AR at an odds ratio of 1.57 for the homozygous genotype comparisons indicating a strong risk for AR. This highlights the importance of this mutation in Asian populations for risk towards allergic phenotypes and also warrants further functional work to characterize the mechanism behind this genetic predisposition.

Polymorphisms in the IL4 gene, smoking, and rhinoconjunctivitis in Japanese women: the Kyushu Okinawa Maternal and Child Health Study

Epidemiological evidence on the relationship between IL4 single nucleotide polymorphisms (SNPs) and allergic rhinitis is limited. We conducted a case-control study to investigate this issue in young adult Japanese women. Included were 393 women who met the criteria of the International Study of Asthma and Allergies in Childhood (ISAAC) for rhinoconjunctivitis. Controls were 703 women without rhinoconjunctivitis based on the ISAAC criteria who had not been diagnosed with allergic rhinitis and/or asthma by a doctor. Compared with the TT genotype of IL4 SNP rs2227284, the GG genotype, occurring in 10.2% of control subjects, was significantly inversely associated with the risk of rhinoconjunctivitis: the adjusted OR was 0.60 (95% CI: 0.37-0.98). There were no significant relationships between SNP rs2243250, rs2070874, or rs2243290 and rhinoconjunctivitis. None of the haplotypes were significantly related to rhinoconjunctivitis. A significant inverse relationship between the combination of the TG and GG genotypes of SNP rs2227284 and rhinoconjunctivitis was observed in women who had never smoked, but not in those who had ever smoked (P for interaction=0.11). This is the first study to demonstrate a significant relationship between IL4 SNP rs2227284 and rhinoconjunctivitis. Smoking may modify the relationship between SNP rs2227284 and rhinoconjunctivitis.