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Table 2 The association of each socioeconomic status with low back pain after multiple data imputations (n = 26,037. Multilevel Poisson regression analysis)

From: Socioeconomic inequalities in low back pain among older people: the JAGES cross-sectional study

Socioeconomic status Model 1 Model 2 Model 3 Model 4
PR 95% CI PR 95% CI PR 95% CI PR 95% CI
Fixed parameter
 Education, years (ref, ≥13)
  10–12 1.05 1.01, 1.10 1.04 0.99, 1.09 1.03 0.99, 1.09 1.03 0.98, 1.08
   < 10 1.12 1.07, 1.17 1.09 1.04, 1.14 1.07 1.02, 1.12 1.05 1.002, 1.10
  P for trend < 0.01 < 0.01 < 0.01 0.01
 Random part
  Municipality level variance (standard error) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001)
Past occupation (ref, professionals)
 Fixed parameter
  White-collared workers 1.02 0.97, 1.07 1.00 0.95, 1.06 1.01 0.95, 1.06 1.01 0.95, 1.06
  Blue-collared workers 1.08 1.03, 1.14 1.06 1.02, 1.11 1.06 1.01, 1.11 1.04 1.001, 1.10
  Never worked before 1.11 1.04, 1.19 1.04 0.97, 1.12 1.03 0.95, 1.12 1.01 0.93, 1.09
  P for trend < 0.01 < 0.01 < 0.01 0.02
 Random part
  Municipality level variance (standard error) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001)
 Income, yen (ref, ≥3 million)
  2 million–2.99 million 1.03 0.98, 1.09 1.03 0.98, 1.08 1.03 0.97, 1.09 1.02 0.97, 1.08
  1 million–1.99 million 1.09 1.04, 1.14 1.09 1.04, 1.14 1.08 1.02, 1.13 1.05 1.002, 1.11
  < 1 million 1.20 1.14, 1.26 1.17 1.11, 1.23 1.16 1.10, 1.23 1.12 1.06, 1.19
  P for trend < 0.01 < 0.01 < 0.01 < 0.01
 Random part
  Municipality level variance (standard error) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001)
Subjective economic situation (ref, very comfortable)
 Fixed parameter
  Comfortable 1.06 1.00, 1.12 1.07 1.004, 1.13 1.05 0.99, 1.12 1.04 0.98, 1.11
  Difficult 1.19 1.12, 1.26 1.21 1.14, 1.29 1.18 1.10, 1.26 1.14 1.07, 1.22
  Very difficult 1.34 1.25, 1.44 1.36 1.26, 1.47 1.32 1.22, 1.44 1.22 1.11, 1.33
  P for trend < 0.01 < 0.01 < 0.01 < 0.01
 Random part
  Municipality level variance (standard error) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001)
Wealth, yen (ref, ≥50 million)
 Fixed parameter
  10 million–49.99 million 1.07 1.01, 1.12 1.07 1.01, 1.12 1.05 0.99, 1.11 1.04 0.98, 1.10
  5 million–9.99 million 1.09 1.03, 1.16 1.09 1.02, 1.15 1.07 1.004, 1.14 1.05 0.98, 1.12
  1 million–4.99 million 1.15 1.09, 1.23 1.14 1.08, 1.22 1.11 1.04, 1.19 1.08 1.01, 1.16
  < 1 million 1.22 1.15, 1.30 1.21 1.14, 1.29 1.18 1.11, 1.27 1.13 1.06, 1.21
  P for trend < 0.01 < 0.01 < 0.01 < 0.01
 Random part
  Municipality level variance (standard error) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001) 0.001 (< 0.001)
  1. Abbreviations: PR prevalence ratio, 95% CI 95% credible interval
  2. Socioeconomic status was separately added to each model. Model 1, a crude model; Model 2, with age and sex adjusted to Model 1; Model 3, with number of persons living together, marital status, musculoskeletal disease, BMI, drinking habit, smoking and physical activity added to Model 2; Model 4, with depression added to Model 3