The results were adjusted for other perinatal risk factors as well as other broadly measured potential confounders.
For instance, in the IDEFICS study we decided to measure potential confounders to enable their control in the statistical analysis instead of controlling them by randomization.
Using high-performance liquid chromatography, they analyzed PAH DNA adduct levels in cord blood collected at delivery and also measured potential confounders for neurodevelopmental effects, including lead, mercury, and secondhand tobacco smoke.
A spatial overlay function within ArcGIS version 10.0 (ESRI, Redlands, CA) was used to intersect these buffers with the tree canopy layer and other geographies used to measure potential confounders: park coverage, traffic volume, and residential composition.
It also captures the urban heat island effect, as shown in Figure 2. In addition, we account for small area measures of potential confounders at a 1 × 1 km spatial resolution such as individual and census measures of socioeconomic status, and medical history.
Pearson correlational analyses were conducted on FMD, SES measures, and potential confounders to detect associations.
The usual strategy for minimizing bias is to seek good measures of potential confounders and then adjust for them.
In addition we account for small area measures of potential confounders at a 10x10km spatial resolution, thus minimizing exposure error.
[ 4] The strengths of our study were that comprehensive measures of potential confounders were available for the entire cohort.
Most studies stated a clear definition of the immigrant groups (n = 29), excluded bias sufficiently (n = 26), adjusted at least some outcome measures for potential confounders (n = 26) and used the same source population for all immigrant groups (n = 35).
