Birth weight, childhood body mass index, and height in relation to mammographic density and breast cancer: a register-based cohort study

Table 4 Effect modification of an association ^a between breast cancer and exposure variables by age and mammographic density in 13,572 women

	Breast cancer N(%)	Birth weight HR (95% CI)	BMI at age 13 HR (95% CI)	Height at age 13 HR (95% CI)
Age at BC diagnoses (years)
50-59 years	193 (27.0)	1.01 (0.75-1.36)	1.03 (0.88-1.22)	1.06 (0.92-1.23)
60⁺ years	523 (73.0)	0.82 (0.66-1.02)	1.00 (0.90-1.11)	1.10 (1.00-1.20)
P value for interaction		0.31	0.81	0.69
Mammographic density
Mixed/dense breasts	541 (75.5)	0.88 (0.72-1.07)	1.02 (0.92-1.14)	1.13 (1.03-1.23)
Fatty breasts	175 (24.4)	0.92 (0.62-1.36)	1.00 (0.81-1.17)	0.97 (0.83-1.13)
P value for interaction		0.85	0.70	0.08
Total	716	0.89 (0.75-1.06)	1.01 (0.93-1.11)	1.09 (1.01-1.17)

CI, confidence interval; HR, hazard ratio; ^aAdjusted for age (underlying time scale) and mammographic density, and stratified by birth cohort (1930 to 1934, 1935 to 1939, 1940 to 1944, 1945 to 1949).

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