Maternal height and breast cancer risk: results from a study nested within the EPIC-Greece cohort.

The positive association of adult height with breast cancer (BC) risk has been hypothesized to be partly accounted for by an association of this risk with maternal height (operating in utero to modify hormone effects). In a case-control study (271 BC patients and 791 controls) nested within the EPIC-Greece cohort, we applied mediation analysis to calculate the direct and indirect (through the woman's own height) effect of maternal height on BC risk. Per 5 cm increase in maternal height and depending on its reference value: the indirect effect odds ratio ranges from 1.02 to 1.07; the direct effect odds ratio from 1.06 to 1.11; and the total (direct and indirect effects) from 1.08 to 1.19. The effect sizes consistently increased for higher reference categories of maternal height, but did not generally reach statistical significance, possibly due to the limited sample size.