Table 3 Interaction and mediation of periodontitis and systemic inflammation regarding mortality

Interaction

 Model A: Fully adjusted cox proportional hazards model

  Inflammation measure

1.335 (1.188; 1.501)

 < 0.001

1.191 (1.071; 1.325)

0.001

1.361 (1.113; 1.663)

0.003

1.172 (0.969; 1.417)

0.101

1.330 (1.151; 1.537)

 < 0.001

1.198 (1.054; 1.363)

0.006

  Periodontitis measure

1.380 (1.191; 1.599)

 < 0.001

1.184 (1.079; 1.300)

 < 0.001

1.384 (1.063; 1.801)

0.016

1.204 (1.023; 1.417)

0.025

1.380 (1.154; 1.649)

 < 0.001

1.174 (1.047; 1.316)

0.006

 Model B: Model A + inclusion of a multiplicative interaction term and post hoc RERI calculation

  Inflammation measure

1.268 (1.053; 1.528)

0.012

1.201 (1.050; 1.374)

0.007

1.174 (0.816; 1.689)

0.387

1.014 (0.781; 1.315)

0.919

1.328 (1.069; 1.650)

0.010

1.282 (1.099; 1.496)

0.002

  Periodontitis measure

1.357 (1.164; 1.583)

 < 0.001

1.190 (1.072; 1.320)

0.001

1.320 (1.000; 1.744)

0.050

1.120 (0.929; 1.351)

0.236

1.379 (1.145; 1.661)

0.001

1.222 (1.079; 1.385)

0.002

  Multiplicative interaction

1.054 (0.910; 1.220)

0.482

0.991 (0.910; 1.079)

0.838

1.143 (0.872; 1.499)

0.333

1.129 (0.976; 1.306)

0.102

1.001 (0.840; 1.194)

0.987

0.922 (0.830; 1.025)

0.132

RERI (95% CI)

P-value

RERI (95% CI)

P-value

RERI (95% CI)

P-value

RERI (95% CI)

P-value

RERI (95% CI)

P-value

RERI (95% CI)

P-value

  Additive Interaction

0.189 (0.000; 0.378)

0.050

0.026 (− 0.072; 0.123)

0.607

0.278 (− 0.025; 0.581)

0.072

0.148 (0.013; 0.283)

0.032

0.127 (− 0.116; 0.370)

0.305

 − 0.059 (− 0.190; 0.072)

0.378

Mediation

 Model C: Mediation analysis considering inflammation as a mediator for the association between periodontitis and mortality

  Total effect

1.322 (1.121; 1.559)

0.001

1.143 (1.077; 1.214)

 < 0.001

1.304 (0.968; 1.757)

0.080

1.020 (0.898; 1.160)

0.756

1.338 (1.096; 1.633)

0.004

1.176 (1.096; 1.262)

 < 0.001

  Direct effect

1.304 (1.106; 1.538)

0.002

1.134 (1.069; 1.202)

 < 0.001

1.285 (0.955; 1.730)

0.098

1.028 (0.910; 1.161)

0.656

1.321 (1.082; 1.613)

0.006

1.160 (1.082; 1.243)

 < 0.001

  Indirect effect

1.014 (1.002; 1.026)

0.027

1.008 (1.001; 1.016)

0.027

1.015 (0.995; 1.035)

0.140

0.993 (0.979; 1.006)

0.291

1.013 (0.998; 1.027)

0.080

1.014 (1.005; 1.024)

0.002

 Model D: Mediation analysis considering periodontitis as a mediator for the association between inflammation and mortality

  Total effect

1.187 (0.982; 1.436)

0.076

1.108 (0.982; 1.250)

0.096

1.089 (0.742; 1.597)

0.664

0.942 (0.743; 1.193)

0.618

1.226 (0.985; 1.525)

0.068

1.175 (1.022; 1.351)

0.024

  Direct effect

1.166 (0.956; 1.421)

0.046

1.101 (0.975; 1.244)

0.121

1.065 (0.714; 1.589)

0.756

0.934 (0.736; 1.186)

0.574

1.204 (0.959; 1.512)

0.110

1.169 (1.015; 1.346)

0.030

  Indirect effect

1.019 (1.000; 1.037)

0.095

1.006 (1.000; 1.012)

0.041

1.022 (0.990; 1.055)

0.182

1.008 (0.998; 1.018)

0.099

1.018 (0.997; 1.040)

0.098

1.005 (0.998; 1.012)

0.177