American Association for Cancer Research

Table 2

Breast cancer incidence rates, RRs, and 95% CIs by NSAID type and duration in the WHI Observational Study

Type of NSAID	Duration of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years	Age-adjusted RR			Test for linear trend P
Type of NSAID	Duration of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years				Test for linear trend P	RR	95% CI
Reference^a	0–11 mo	54,102	955	194,884	490.04	1.00	N/A^b	N/A
Any NSAID	1–4 yr	9,000	149	32,127	463.79	0.93	(0.78–1.10)
	≥5 yr	10,162	148	36,576	404.64	0.81	(0.68–0.97)	0.01
Regular aspirin	1–4 yr	5,124	83	18,231	455.27	0.90	(0.72–1.13)
	≥5 yr	6,759	99	24,398	405.76	0.81	(0.66–0.99)	0.03
Ibuprofen	1–4 yr	3,469	51	12,553	406.26	0.83	(0.63–1.10)
	≥5 yr	2,976	42	10,653	394.26	0.82	(0.60–1.12)	0.12
Prescription NSAID	1–4 yr	1,615	31	5,552	558.31	1.14	(0.79–1.62)
	≥5 yr	947	11	3,388	324.71	0.64	(0.36–1.17)	0.21
Acetaminophen	1–4 yr	2,450	44	8,608	511.18	1.02	(0.75–1.37)
	≥5 yr	4,675	79	16,698	473.11	0.96	(0.76–1.20)	0.71

Type of NSAID	Duration of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years	Age-adjusted RR			Test for linear trend P
Type of NSAID	Duration of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years				Test for linear trend P	RR	95% CI
Reference^a	0–11 mo	54,102	955	194,884	490.04	1.00	N/A^b	N/A
Any NSAID	1–4 yr	9,000	149	32,127	463.79	0.93	(0.78–1.10)
	≥5 yr	10,162	148	36,576	404.64	0.81	(0.68–0.97)	0.01
Regular aspirin	1–4 yr	5,124	83	18,231	455.27	0.90	(0.72–1.13)
	≥5 yr	6,759	99	24,398	405.76	0.81	(0.66–0.99)	0.03
Ibuprofen	1–4 yr	3,469	51	12,553	406.26	0.83	(0.63–1.10)
	≥5 yr	2,976	42	10,653	394.26	0.82	(0.60–1.12)	0.12
Prescription NSAID	1–4 yr	1,615	31	5,552	558.31	1.14	(0.79–1.62)
	≥5 yr	947	11	3,388	324.71	0.64	(0.36–1.17)	0.21
Acetaminophen	1–4 yr	2,450	44	8,608	511.18	1.02	(0.75–1.37)
	≥5 yr	4,675	79	16,698	473.11	0.96	(0.76–1.20)	0.71

The reference category includes women who reported 0–11 months of NSAID use (aspirin, ibuprofen, prescription NSAIDs, or the related analgesic, acetaminophen).

N/A, not applicable.

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