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.
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