Inherited factors contribute to an inverse association between preeclampsia and breast cancer

Breast Cancer Research

Table 2 Association between preeclampsia and breast cancer among the nationwide cohort and KARMA cohort

Condition	Number of breast cancer cases	IRR (95% CI)
Condition	Number of breast cancer cases	Model 1	Model 2
Nationwide cohort (N = 1,337,934)
Preeclampsia
No	26447	1.00 (REF)	1.00 (REF)
Yes	1179	0.88 (0.83; 0.94)	0.90 (0.85; 0.96)
once	1082	0.90 (0.84; 0.95)	0.91 (0.86; 0.97)
multiple times	97	0.76 (0.62; 0.92)	0.81 (0.66; 0.99)
KARMA cohort (N = 55,044)
Preeclampsia
No	2410	1.00 (REF)	1.00 (REF)
Yes	86	0.77 (0.62; 0.95)	0.75 (0.61; 0.93) ^a

Model 1 adjusted for calendar period (10-year categories). Model 2 further adjusted for number of births, age at first birth, weight status categories, smoking status and education level. The underlying time scale was attained age. Significant associations are denoted in bold
Abbreviations: IRR incidence rate ratio, CI confidence interval
^aFor model 2 in the KARMA cohort, we additionally adjusted for alcohol use, age at menarche, body shape at age 18 years, physical activity at age 18 years and irregular menstrual cycles in adult life

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