3. Results
In our current study, a total of 6651 participants who responded at
least one of ISSAC questionnaires at 1, 2, 4, and 7 years of age were
included (Figure 1). Participants were grouped by the WHO guidelines for
folate deficiency are as follows: folate deficient: n = 32 (0.48%);
suboptimal: n = 1739 (26.15%); and optimal: n = 4880 (73.37%) (Table
1). Associations of maternal folate levels and characteristics were
shown in Table 2. We found that the adjusted OR of childhood wheeze at 2
years age according to maternal folate levels of quartiles were
significantly increased, compared with that of lowest quartile, but not
1, 4, and 7 years age. Additionally, we found that adjusted
OR2 of childhood wheezing at 2 years age according to
maternal folate levels of WHO guideline was significantly increased
trend (P for trend = 0.023) (Table 3).
In a case-control study, mean ± standard deviation (SD) of DNA
methylation at three CpG sites that ORMDL3 (cg02305874) andIKZF3 (cg16293631, cg13432737) are illustrated in Supplementary
Table 3.We found no significant adjusted β for DNA methylation according
to maternal folate levels (Table 4). We found that adjusted OR for
childhood wheezing at 7 years of age was significantly decreased with
hypomethylation of IKZF3 (cg16293631), but not ORMDL3(cg02305874) and IKZF3 (cg13432737) (Supplementary Table 4). We
found no significant adjusted OR for childhood wheezing at 7 years age
was association maternal folate in the case-control study (Supplementary
Table 4).