In addition, we tested interactional effects of sex by adding an interaction term 'sex × body size (each anthropometric variable at each time point in separate models)' into the regression equation in addition to the main effects of these two centered variables in predicting ADHD-symptoms.
We can explore this possibility by adding an interaction term ( {h}_{it}^mtimes {h}_{it}^f ) to the right-hand side of Eq. (1).
To assess the sex-specific effect, we analyzed male and female data separately and further confirmed in the regression model by adding an interaction variable (genotypes*sex) with adjustment for conventional risk factors.
Multiplicative interaction was assessed by adding an interaction variable (HLA-SE* smoking) to the regression models.
The association of NSE and hypothermia treatment was analyzed by adding an interaction term into the logistic regression model.
Multiplicative interaction was assessed by adding an interaction term (for example HLA-SE* smoking) to the regression models.
Interaction between maternal smoking and preterm birth was also tested by adding an interaction term in the multivariate models.
In addition, we formally evaluated these associations by adding an interaction term (ε4 * NSAID use) to the GEE model.
Differences in trends between the age categories were investigated by adding an interaction term to the model.
The potential interaction between T3/TSH and menopausal status was tested by adding an interaction term in the Cox analysis.
Effect modification by obesity (cutpoint, 30 kg/m for body mass index) and sex was evaluated by adding an interaction term in the main model.
