Statistical analysis
The data were analyzed using SPSS version 21.0 (SPSS, Chicago, IL) and R
software version 3.6.3. Continuous data are expressed as means with
standard deviations or as medians with the interquartile ranges,
depending on the data distribution. The relationships of the
concentrations of different of urinary phthalates with serum periostin
level, Rrs5, and Rrs5-20 were analyzed using linear regression with
adjustment for height, gender, BMI z -score, aeroallergen
sensitization, secondary smoking, and vitamin D level. The estimates
were regression slopes for phthalate concentration vs. periostin
level and Rrs5. Beta (β) and a 95% confidence interval (CI) were
obtained from a generalized linear regression model with the gamma
function. The R package, “Mediation”19 was used to
quantitatively estimate the mediating effect of periostin level in the
association of phthalate concentration with Rrs5 and Rrs5-20. This
package estimates confidence intervals using bootstrapping with 1000
resamples. A two-sided P value of .05 or less indicated
statistical significance.