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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 baselinenBreast cancer casesPerson-years at riskIncidence per 100,000 person-yearsAge-adjustedMultivariate-adjusteda
RR95% CIRR95% CI
BMI (kg/m2        
 <27         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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 baselinenBreast cancer casesPerson-years at riskIncidence per 100,000 person-yearsAge-adjustedMultivariate-adjusteda
RR95% CIRR95% CI
BMI (kg/m2        
 <27         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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         
  <1b 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) 
a

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).

b

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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