This observation differs from the present finding of no effect modification by body weight.
Effect modification by body mass index [ 27] and country were assessed, and several sensitivity analyses were conducted (Additional file 1).
In a pooled-analysis, however, no significant effect modification by body mass index on the association between alcohol consumption and breast cancer risk was found [ 20, 21].
No significant effect modification by body mass index, physical activity level, glycemic load, aspirin or lipid lowering medication use was observed.
There was no evidence for effect modification by body mass index, physical activity, menopausal status, and hormone replacement therapy use combined and effects did not differ by type of endometrial cancer (type I or II).
We examined potential effect modification by body mass index (BMI), waist:hip ratio, diabetes, physical activity, age, sex, and race/ethnicity in fully adjusted models by including the corresponding multiplicative interaction term(s).
Previous studies have also found evidence of effect modification by body weight (Lee et al. 2006); however, those results as well as ours are limited by a lack of data on recent weight loss.
The mechanism behind the observed effect modification by body mass index also needs further exploration, as no excess risks were observed for preterm or for small for gestational age birth in women who were morbidly obese.
Several case control studies also suggested effect modification by body mass index, with the effect of moderate alcohol consumption limited to women with low or normal BMI [ 18, 19].
In the present study, BMI did not modify the effect of DDE on incident diabetes, but effect modification by body weight was found in several cross-sectional studies (Cox et al. 2007; Lee et al. 2007a).
