Table 3 Adjusted relative riska of breast cancer in regularly, irregularly and never-screenedb New Zealand women, breast cancers diagnosed 2003–2011

From: Mammography service screening and breast cancer mortality in New Zealand: a National Cohort Study 1999–2011

Variable Regression estimate (s.e.) P -value Relative risk (95% CI) % Mortality difference (95% CI)
Screening status
Never screened    1.00 0
Not screened regularly −0.8685 (0.1117) <0.0001 0.42 (0.34–0.52) −58 (−66 to −48)
Not screened regularly (adj.)c 0.74 (0.65–0.83) −26 (−35 to −17)
Not screened regularly (adj.)d 0.69 (0.60–0.79) −31 (−40 to −21)
Not screened regularly (adj.)e 0.69 (0.61–0.79) −31 (−39 to −21)
Screened regularlyb 1.1231 (0.2622) <0.0001 0.33 (0.19–0.54) −67 (−81 to −46)
Screened regularly (adj.)c 0.67 (0.55–0.82) −33 (−45 to −18)
Screened regularly (adj.)d 0.61 (0.48–0.78) −39 (−52 to −22)
Screened regularly (adj.)e 0.62 (0.49–0.78) −38 (−51 to −22)
Screening category trend testf: χ2(1)=25:6 <0.0001   
Age at death (years)
60–64 (referent)    1.00  
45–49 0.1149 (0.0696) 0.0987 1.12 (0.98–1.29)  
50–54 −0.2360 (0.0736) 0.0013 0.79 (0.68–0.91)  
55–59 −0.1400 (0.0328) <0.0001 0.87 (0.82–0.93)  
65–69 0.0006 (0.0654) 0.9924 1.00 (0.88–1.14)  
70–74 −0.1312 (0.0750) 0.0802 0.88 (0.76–1.02)  
75–79 −0.2142 (0.0863) 0.0131 0.81 (0.68–0.96)  
Ethnicity
Other    1.00  
Māori 0.5925 (0.0409) <0.0001 1.81 (1.67–1.96)  
Pacific 0.5550 (0.0586) <0.0001 1.74 (1.55–1.95)  
Intercept −8.9849 (0.0932) <0.0001
  1. Abbreviation: CI=confidence interval.
  2. aFrom negative binomial regression model adjusted for repeat measures.
  3. bScreened 3 times, 30 months mean screening interval, as screened by BreastScreen Aotearoa.
  4. cAdjusted for screening selection bias, assuming relative risk in non-screeners to women not offered screening=1.17 and mean screening participation rate of 64% for 2001–2011.
  5. dAdjusted for screening selection bias, assuming relative risk in non-screeners to women not offered screening=1.17 and recorded screening participation rate of 71% for 2012–2013.
  6. eAdjusted for screening selection bias, assuming relative risk in non-screeners to women not offered screening=1.17 and target screening participation rate of 70%.
  7. fTrend test from regressing screening category as ordinal variable: no screening=1; irregular screening=2; regular screening=3.