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
Referencea0–11 mo54,102955194,884490.041.00N/AbN/A
Any NSAID1–4 yr9,00014932,127463.790.93(0.78–1.10)
≥5 yr10,16214836,576404.640.81(0.68–0.97)0.01
Regular aspirin1–4 yr5,1248318,231455.270.90(0.72–1.13)
≥5 yr6,7599924,398405.760.81(0.66–0.99)0.03
Ibuprofen1–4 yr3,4695112,553406.260.83(0.63–1.10)
≥5 yr2,9764210,653394.260.82(0.60–1.12)0.12
Prescription NSAID1–4 yr1,615315,552558.311.14(0.79–1.62)
≥5 yr947113,388324.710.64(0.36–1.17)0.21
Acetaminophen1–4 yr2,450448,608511.181.02(0.75–1.37)
≥5 yr4,6757916,698473.110.96(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.