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Table 2

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

Type of NSAIDDuration of use at baselinenBreast cancer casesPerson-years at riskIncidence per 100,000 person-yearsAge-adjusted RRTest for linear trend P
RR95% CI
Referencea 0–11 mo 54,102 955 194,884 490.04 1.00 N/Ab 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 NSAIDDuration of use at baselinenBreast cancer casesPerson-years at riskIncidence per 100,000 person-yearsAge-adjusted RRTest for linear trend P
RR95% CI
Referencea 0–11 mo 54,102 955 194,884 490.04 1.00 N/Ab 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 
a

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

b

N/A, not applicable.

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