American Association for Cancer Research

Table 3

Age- and multivariate-adjusted RRs and 95% CIs relating baseline intake of any NSAID to incident breast cancer in selected strata of women in the WHI Observational Study

Strata and years of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years	Age-adjusted			Multivariate-adjusted^a
Strata and years of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years					RR	95% CI	RR	95% CI
BMI (kg/m²)
<27
<1^b	31,622	547	115,363	474	1.00		1.00
1–4	4,510	81	16,372	495	1.02	(0.81–1.29)	0.91	(0.70–1.17)
≥5	5,529	81	20,150	402	0.83	(0.66–1.05)	0.80	(0.63–1.02)
≥27
<1^b	21,825	400	77,034	519	1.00		1.00
1–4	4,399	65	15,421	422	0.80	(0.61–1.04)	0.77	(0.58–1.03)
≥5	4,519	67	16,006	419	0.79	(0.61–1.03)	0.71	(0.53–0.95)
HRT use (ever)
No
<1^b	22,340	323	80,338	402	1.00		1.00
1–4	3,310	47	11,850	397	0.97	(0.71–1.31)	0.89	(0.64–1.26)
≥5	3,465	41	12,531	327	0.80	(0.58–1.11)	0.75	(0.52–1.08)
Yes
<1^b	31,762	632	114,546	552	1.00		1.00
1–4	5,690	102	20,276	503	0.89	(0.72–1.10)	0.82	(0.65–1.03)
≥5	6,697	107	24,045	445	0.78	(0.64–0.96)	0.76	(0.61–0.95)
Family history of breast cancer
No
<1^b	41,813	669	151,486	442	1.00		1.00
1–4	6,841	112	24,501	457	1.01	(0.83–1.24)	0.93	(0.75–1.15)
≥5	7,742	107	27,922	383	0.85	(0.69–1.04)	0.81	(0.66–1.00)
Yes
<1^b	9,407	237	33,667	704	1.00		1.00
1–4	1,645	25	5,886	425	0.59	(0.39–0.90)	0.60	(0.38–0.92)
≥5	1,901	32	6,843	468	0.65	(0.45–0.95)	0.62	(0.41–0.93)
Parous under age 30
No
<1^b	11,204	236	40,429	584	1.00		1.00
1–4	1,677	34	6,095	558	0.93	(0.65–1.33)	0.87	(0.59–1.27)
≥5	1,937	34	7,068	481	0.81	(0.56–1.16)	0.78	(0.54–1.13)
Yes
<1^b	37,228	648	134,506	482	1.00		1.00
1–4	6,463	103	23,022	447	0.91	(0.74–1.12)	0.84	(0.67–1.04)
≥5	7,335	102	26,297	388	0.79	(0.64–0.98)	0.75	(0.61–0.94)
Episodes/wk of moderate to strenuous exercise (≥20 min)
<2
<1^b	27,105	457	95,813	477	1.00		1.00
1–4	4,762	61	16,771	364	0.75	(0.58–0.98)	0.70	(0.52–0.93)
≥5	5,273	77	18,796	410	0.85	(0.67–1.08)	0.76	(0.59–0.99)
≥2
<1^b	26,266	475	95,621	497	1.00		1.00
1–4	4,140	88	14,855	592	1.16	(0.92–1.46)	1.00	(0.77–1.29)
≥5	4,805	71	17,375	409	0.81	(0.63–1.03)	0.76	(0.58–0.98)

Strata and years of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years	Age-adjusted			Multivariate-adjusted^a
Strata and years of use at baseline	n	Breast cancer cases	Person-years at risk	Incidence per 100,000 person-years					RR	95% CI	RR	95% CI
BMI (kg/m²)
<27
<1^b	31,622	547	115,363	474	1.00		1.00
1–4	4,510	81	16,372	495	1.02	(0.81–1.29)	0.91	(0.70–1.17)
≥5	5,529	81	20,150	402	0.83	(0.66–1.05)	0.80	(0.63–1.02)
≥27
<1^b	21,825	400	77,034	519	1.00		1.00
1–4	4,399	65	15,421	422	0.80	(0.61–1.04)	0.77	(0.58–1.03)
≥5	4,519	67	16,006	419	0.79	(0.61–1.03)	0.71	(0.53–0.95)
HRT use (ever)
No
<1^b	22,340	323	80,338	402	1.00		1.00
1–4	3,310	47	11,850	397	0.97	(0.71–1.31)	0.89	(0.64–1.26)
≥5	3,465	41	12,531	327	0.80	(0.58–1.11)	0.75	(0.52–1.08)
Yes
<1^b	31,762	632	114,546	552	1.00		1.00
1–4	5,690	102	20,276	503	0.89	(0.72–1.10)	0.82	(0.65–1.03)
≥5	6,697	107	24,045	445	0.78	(0.64–0.96)	0.76	(0.61–0.95)
Family history of breast cancer
No
<1^b	41,813	669	151,486	442	1.00		1.00
1–4	6,841	112	24,501	457	1.01	(0.83–1.24)	0.93	(0.75–1.15)
≥5	7,742	107	27,922	383	0.85	(0.69–1.04)	0.81	(0.66–1.00)
Yes
<1^b	9,407	237	33,667	704	1.00		1.00
1–4	1,645	25	5,886	425	0.59	(0.39–0.90)	0.60	(0.38–0.92)
≥5	1,901	32	6,843	468	0.65	(0.45–0.95)	0.62	(0.41–0.93)
Parous under age 30
No
<1^b	11,204	236	40,429	584	1.00		1.00
1–4	1,677	34	6,095	558	0.93	(0.65–1.33)	0.87	(0.59–1.27)
≥5	1,937	34	7,068	481	0.81	(0.56–1.16)	0.78	(0.54–1.13)
Yes
<1^b	37,228	648	134,506	482	1.00		1.00
1–4	6,463	103	23,022	447	0.91	(0.74–1.12)	0.84	(0.67–1.04)
≥5	7,335	102	26,297	388	0.79	(0.64–0.98)	0.75	(0.61–0.94)
Episodes/wk of moderate to strenuous exercise (≥20 min)
<2
<1^b	27,105	457	95,813	477	1.00		1.00
1–4	4,762	61	16,771	364	0.75	(0.58–0.98)	0.70	(0.52–0.93)
≥5	5,273	77	18,796	410	0.85	(0.67–1.08)	0.76	(0.59–0.99)
≥2
<1^b	26,266	475	95,621	497	1.00		1.00
1–4	4,140	88	14,855	592	1.16	(0.92–1.46)	1.00	(0.77–1.29)
≥5	4,805	71	17,375	409	0.81	(0.63–1.03)	0.76	(0.58–0.98)

Estimates are adjusted for age, ethnicity, education, and main effects of remaining covariates (BMI, HRT use, family history of breast cancer, parous under age 30, and episodes per week of moderate to strenuous exercise).

The reference category is 0–11 months of NSAID use (aspirin, ibuprofen, prescription NSAIDs, or the related analgesic, acetaminophen), within each breast cancer risk factor strata.

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