Figure 1.

Multivariable adjusted hazard ratios (HR) and 95% confidence intervals (CI) for breast cancer among parous women according to timing of smoking initiation in relation to first childbirth (never, at time of/after and before) by tumour receptor status and race/ethnicity, the Multiethnic Cohort study, 1993–2013^a,b,c. ^aAdjusted for race/ethnicity where applicable, age at cohort entry, body mass index, family history of breast cancer, age at first childbirth, number of children, age at menarche, age at and type of menopause, postmenopausal hormone therapy, alcohol intake, and education. ^bParous women (n = 58 119) and 5 racial/ethnic groups for all invasive breast cancer cases (n = 3 592), with at least one tumour receptor status. ^cParous never smokers as reference group.