Table 2 Multivariable HRs (95% CI) for the association of post-diagnostic regular aspirin use with breast cancer-specific mortality and total mortality in the Nurses’ Health Studies (10,705 breast cancer cases with 131,940 follow-up years)

	Breast cancer-specific mortality		Total mortality
	Regular aspirin use (≥2 days/week)		Regular aspirin use (≥2 days/week)
	Nonuser	Aspirin user	Nonuser	Aspirin user
Overall
No. of events	908	347	1,766	1,059
Person years	77,396	54,545	77,396	54,545
Age-adjusted	1.0 (ref)	0.56 (0.49, 0.63)	1.0 (ref)	0.67 (0.62, 0.72)
Age- and pre-diagnostic aspirin-adjusted	1.0 (ref)	0.53 (0.46, 0.60)	1.0 (ref)	0.64 (0.59, 0.69)
Multivariable^a adjusted	1.0 (ref)	0.62 (0.54, 0.71)	1.0 (ref)	0.72 (0.66, 0.78)
5-year mortality
No. of events	408	142	576	272
Person years	26,365	14,227	26,365	14,227
Age-adjusted	1.0 (ref)	0.67 (0.55, 0.81)	1.0 (ref)	0.74 (0.64, 0.86)
Age- and pre-diagnostic aspirin-adjusted	1.0 (ref)	0.60 (0.48, 0.74)	1.0 (ref)	0.65 (0.55, 0.76)
Multivariable^a adjusted	1.0 (ref)	0.74 (0.59, 0.92)	1.0 (ref)	0.75 (0.64, 0.89)
>5-to-15-year mortality
No. of events	403	158	815	482
Person years	37,840	27,187	37,840	27,187
Age-adjusted	1.0 (ref)	0.52 (0.43, 0.63)	1.0 (ref)	0.65 (0.58, 0.73)
Age- and pre-diagnostic aspirin-adjusted	1.0 (ref)	0.50 (0.42, 0.61)	1.0 (ref)	0.63 (0.56, 0.70)
Multivariable^a adjusted	1.0 (ref)	0.60 (0.49, 0.72)	1.0 (ref)	0.71 (0.63, 0.80)
>15-year mortality
No. of events	97	47	375	305
Person years	13,190	13,130	13,190	13,130
Age-adjusted	1.0 (ref)	0.47 (0.33, 0.67)	1.0 (ref)	0.71 (0.61, 0.83)
Age- and pre-diagnostic aspirin-adjusted	1.0 (ref)	0.47 (0.33, 0.66)	1.0 (ref)	0.70 (0.60, 0.82)
Multivariable^a adjusted	1.0 (ref)	0.50 (0.35, 0.72)	1.0 (ref)	0.75 (0.64, 0.87)

^aMultivariable model adjusted for age at diagnosis (continuous), calendar year of diagnosis (continuous), pre-diagnostic aspirin use (never, past, current, missing), stage (I, II, III), chemotherapy (yes, no, missing), hormone therapy (yes, no, missing), radiotherapy (yes, no, missing), pre-diagnostic BMI (normal weight, overweight, obese, missing), change in BMI from pre- to post-diagnosis (>2 kg/m², ≤2 and >−0.5 kg/m², ≤−0.5 kg/m², missing), post-diagnostic physical activity (by quartile, missing), post-diagnostic smoking (current, past, never, missing), neighborhood socioeconomic status (nSES) (by quartile, missing), pre-diagnostic oral contraceptive use (ever, never, missing), pre-diagnostic menopausal hormone replacement therapy use (ever, never, missing), parity (parous, non-parous/unknown), menopausal status prior to diagnosis (premenopausal, postmenopausal, unknown), estrogen receptor status (positive, negative, missing), and propensity score. Propensity score was calculated by estimating the probability of regular use of aspirin based on age (continuous), BMI (normal weight, overweight, obese, unknown), physical activity (by quartile, missing), neighborhood socioeconomic status (nSES) (by quartile, missing), history of angina (yes, no), history of myocardial infarction (yes, no), history of stroke (yes, no), history of rheumatoid arthritis (yes, no).

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