Table 3 Multivariable association between individual income and periodontitis in the entire sample, stratified by interdental brushing behavior and age

Model 1

N = 13,625

N = 10,904

N = 2,721

Low

1.347 (1.148–1.581)

1.357 (1.145–1.608)

1.318 (0.945–1.838)

Middle low

1.244 (1.076–1.438)

1.196 (1.022–1.399)

1.391 (1.018–1.901)

Middle high

1.059 (0.918–1.222)

1.054 (0.898–1.236)

1.069 (0.781–1.464)

High

Reference

Reference

Reference

Model 2

N = 13,621

N = 10,901

N = 2,720

Low

1.258 (1.070–1.478)

1.255 (1.056–1.492)

1.240 (0.890–1.727)

Middle low

1.175 (1.015–1.361)

1.139 (0.971–1.337)

1.345 (0.980–1.844)

Middle high

1.027 (0.888–1.187)

1.031 (0.878–1.212)

1.010 (0.739–1.383)

High

Reference

Reference

Reference

Model 3

N = 12,427

N = 9,883

N = 2,544

Low

1.266 (1.066–1.502)

1.276 (1.061–1.533)

1.193 (0.839–1.696)

Middle low

1.154 (0.986–1.352)

1.113 (0.934–1.326)

1.351 (0.976–1.868)

Middle high

1.057 (0.907–1.232)

1.074 (0.906–1.274)

1.011 (0.736–1.390)

High

Reference

Reference

Reference

Model 3 (19–64 yrs. group)

N = 9,843

N = 7,609

N = 2,234

Low

1.276 (1.050–1.549)

1.301 (1.052–1.608)

1.154 (0.793–1.681)

Middle low

1.160 (0.965–1.394)

1.120 (0.914–1.372)

1.324 (0.931–1.883)

Middle high

1.055 (0.881–1.263)

1.076 (0.879–1.316)

1.001 (0.704–1.422)

High

Reference

Reference

Reference

Model 3 (over 65 yrs)

N = 2,584

N = 2,274

N = 310

Low

1.109 (0.830–1.483)

0.988 (0.967–1.011)

1.392 (0.566–3.425)

Middle low

1.064 (0.808–1.402)

1.062 (0.781–1.444)

1.688 (0.806–3.532)

Middle high

1.058 (0.821–1.363)

1.058 (0.805–1.391)

1.009 (0.530–1.921)

High

Reference

Reference

Reference