Concepts of (A) confounding and (B) mediation in epidemiological studies illustrated using a Directed acyclic graph (DAG).

<p>In the case of sex and asthma, where sex is the exposure and asthma status the outcome, any extraneous factors must go by the mediation pathway, as nothing can influence a child’s sex at conception.</p

Male odds ratios for ever wheeze, ever asthma and wheeze in the last 12 months in the MCS at 4 time-points.

<p>Male odds ratios for ever wheeze, ever asthma and wheeze in the last 12 months in the MCS at 4 time-points.</p

Characteristics of wheeze and asthma outcomes in the MCS by sex, with follow-up rates at each time-point as a percentage of total cohort size for each sex (total MCS = 8850 males and 8458 females).

<p>Characteristics of wheeze and asthma outcomes in the MCS by sex, with follow-up rates at each time-point as a percentage of total cohort size for each sex (total MCS = 8850 males and 8458 females).</p

Estimated prevalence of wheezing at each time-point from 3.1 to 10.7 years for each of the four wheezing phenotypes identified by latent class analysis in 7349 participants with complete observations of wheeze in the last 12 months in the MCS.

<p>Estimated prevalence of wheezing at each time-point from 3.1 to 10.7 years for each of the four wheezing phenotypes identified by latent class analysis in 7349 participants with complete observations of wheeze in the last 12 months in the MCS.</p

Longitudinal logistic models using cubic splines of repeated wheeze and asthma measures by sex.

<p>Males are in blue and females in red. Shaded areas represent 95% confidence intervals. Measures of (A) asthma in the last 12 months in ALSPAC (B) wheeze in the last 12 months in ALSPAC (C) asthma ever in the MCS (D) wheeze in the last 12 months in the MCS and (E) wheeze ever in the MCS.</p

Characteristics of wheeze and asthma outcomes in ALSPAC by sex, with follow-up rates at each time-point as a percentage of total cohort size for each sex (total ALSPAC = 7,544 males and 7,155 females).

<p>Characteristics of wheeze and asthma outcomes in ALSPAC by sex, with follow-up rates at each time-point as a percentage of total cohort size for each sex (total ALSPAC = 7,544 males and 7,155 females).</p

Male odds ratios for wheeze in the last 12 months and asthma in the last 12 months, in ALSPAC.

<p>Male odds ratios for wheeze in the last 12 months and asthma in the last 12 months, in ALSPAC.</p

Additional file 2: of Epigenome-wide association study of asthma and wheeze in childhood and adolescence

Supplementary EWAS Tables E. (XLSX 2170 kb