Table 2

Semiparametric generalised additive models for the odds of reported prescription opioid use with smooth function for the effect of age, varying by SES measure

Parametric coefficientsOpioid use (model including income)Opioid use (model including employment status)Opioid use (model including education)
OR (95% CI)OR (95% CI)OR (95% CI)
Intercept0.009 (0.007 to 0.011)***0.003 (0.002 to 0.003)***0.01 (0.007 to 0.011)***
Female (ref: male)1.32 (1.21 to 1.43)***1.53 (1.40 to 1.67)***1.33 (1.22 to 1.44)***
White (ref: not white)2.24 (1.86 to 2.70)***2.01 (1.67 to 2.42)***1.94 (1.61 to 2.32)***
Urban (ref: rural)1.27 (1.15 to 1.41)***1.20 (1.08 to 1.33)***1.29 (1.17 to 1.43)***
Income decile (ref: 1— lowest)
20.93 (0.76 to 1.13)
31.01 (0.82 to 1.24)
40.80 (0.65 to 0.99)*
50.55 (0.43 to 0.70)***
60.51 (0.40 to 0.64)***
70.38 (0.29 to 0.49)***
80.34 (0.26 to 0.44)***
90.40 (0.32 to 0.51)***
10—highest0.27 (0.21 to 0.36)***
 Income missing0.64 (0.53 to 0.77)***
Economic status (ref: employed)
Student0.92 (0.36 to 2.35)
Unemployed1.61 (0.97 to 2.64)
Ill or disabled16.50 (13.24 to 20.55)***
Retired1.60 (0.93 to 2.76)
Domestic worker1.60 (1.32 to 1.94)***
Other3.14 (2.02 to 4.87)***
Education (ref: no qualifications)
Higher education0.48 (0.41 to 0.57)***
A-levels0.57 (0.47 to 0.70)***
O-levels/GCSE0.71 (0.61 to 0.83)***
Foreign/other0.63 (0.43 to 0.91)*
Student0.57 (0.44 to 0.82)**
Non-parametricEDFEDFEDF
Income decile
1—lowest3.97***
26.08***
34.17***
43.31***
52.64***
62.51***
72.06***
81.52***
91.04***
10—highest1.01***
Income missing3.30***
Economic status
Employed1.01***
Student1.002
Unemployed1.002*
Ill or disabled3.12***
Retired4.99**
Domestic worker2.74***
Other1.76*
Education
Higher education2.03***
A-levels2.93***
O-levels/GCSE3.30***
No qualifications4.30***
Foreign/other1.01 **
Student2.81 ***
  • *P value <0.05, **p value <0.01, ***p value <0.001.

  • EDF, estimated degrees of freedom; GCSE, General Certificate of Secondary Education; SES, socioeconomic status.