For each study the literature reference, wellbeing measure, name of the study cohort, age of the sample, gender of the sample, sample size (per zygosity if provided), twin (-family) correlations, and estimates of standardized variance components are provided.
In the current study, there are few limitations regarding age and gender of samples used as well as their ethnicity that is limited to Iranian girls.
Our analysis shows that an allele frequency biplot for the X chromosome can classify the gender of samples donors [Additional file 10, Supplemental Figure S10].
Following normalization, all probes containing SNPs and probes mapped to sex chromosomes were filtered out to prevent bias due to unknown genetic background and mixed gender of samples, respectively, yielding 470,870 probes for subsequent analysis.
The preliminary multinomial regression models described above employed list-wise deletion, and hence sample sizes varied from the full sample of 7218 for gender to samples of down to 4000 for some of the less complete measures.
Clinical data including age at diagnosis, body mass index (BMI), gender, date of sample procurement, date and type of first complication and surgery, medication and disease location were obtained or updated, respectively, for each single visit and time point of sample procurement separately by the treating physician of the IBD unit.
In addition, the association of each individual marker with the disease was tested by fitting a logistic regression genotypic model in which gender, Center of sample origin and HLA-DRB1*1501 status were included as covariates.
The participant characteristics coded in the samples of each study were: (a) the mean age of the subjects (in years); (b) the gender of the sample (percentage of males); (c) the physical activity level of subjects during the intervention (low, moderate, regular), and (d) whether or not they had undertaken previous treatments.
There were no significant differences in the age and gender of study sample as compared with the non-consenting cardiac rehabilitation classes from which they had been recruited (Additional file 1).
Gender of the sample was approximately evenly distributed (χ2 = 0.000, p = 1.000); the mean (sd) age was 10.36 (0.98) years.
Gender of each sample was checked with the number of heterozygosities at SNPs on chromosome X and the relatedness of individuals was analysed using the GRR program [71].
