The results of effect modification by subgroup analysis showed positive associations between 1-year PM2.5abs air pollution exposure and CIMT at LCCA among female and subjects without hypercholesterolemia, never smokers, and non-obese (see Supplemental Material, Table S3).
In this way, any modification between specific subgroups of one variable in relation to specific subgroups of the other variables could be detected.
To evaluate effect modification by smoking, subgroup analyses were also performed for LIG4 rs1805388 and XRCC4 rs1805377 polymorphisms.
To identify susceptible subgroups, we also analyzed effect modification by genes of the antioxidant defense family and the hemochromatosis gene (HFE).
Additional analyses will be conducted to look for evidence of effect modification by pre-specified subgroups: baseline HbA1c (< median, > median) and by English as primary language (Y/N).
Further analyses will be conducted to look for evidence of effect modification by pre-specified subgroups: starting systolic BP (≥ 160 vs. <160), by English as primary language (Y/N), and age (< median versus ≥ median).
Additional analyses will be conducted to look for evidence of effect modification by pre-specified subgroups: baseline HbA1c (<9 versus ≥9), SBP (<160 versus ≥160), LDL (< versus ≥ median), language (English primary versus English not primary), and age (<versus ≥ median).
To consider possible effect modification, we evaluated associations by subgroups defined as above or below the median for age, BMI, years of smoking, number of cigarettes smoked per day, alcohol intake and serum cholesterol.
In case there is no effect modification by treatment the data of both subgroups will be pooled.
When assessing effect modification by looking at overlap of the 95% confidence intervals in subgroups, a type 1 error probability of 0.05 is often mistakenly assumed.
