Table 4

Mediation analysis to evaluate the effects of PAH body burden on the relationship between smoking and rheumatoid arthritis

PAH subset
Indirect effect* of current smoking mediated by PAH0.7626
Indirect effect of past smoking mediated by PAH0.0684
Total indirect (mediated) effect of smoking0.831
Direct effect of current smoking0.0874
Direct effect of past smoking0.0168
Total direct effect of smoking0.1042
Total effect† of current smoking0.8499
Total effect of past smoking0.0852
Total effect of smoking0.9352
Percent of total effect (current smoking) mediated‡89.72
Percent of total effect (past smoking) mediated80.28
Percent of total effect mediated88.86
  • PAH subset (n=7090) with PAH subsample weights used for analysis.

  • Adjustment includes age, sex (male vs female), race (non-Hispanic white vs non-Hispanic black vs Mexican-American vs other), education (high school or less vs more than high school), family poverty income ratio, smoking (never vs past vs current), body mass index, urine creatinine, any vigorous or moderate activity (yes vs no) and dietary fibre.

  • *The effects are obtained from the linear predictors (log(OR)) of logistic regression models and represent a measure of association where positive values mean the variable increases the likelihood of the outcome.

  • †Total effect=direct+indirect effect.

  • ‡Percent of total effect mediated=100*(indirect/total).

  • PAHs, polycyclic aromatic hydrocarbons.