Table 7 Mediation analysis: Pathways linking smoking to ACOS risk.
From: Exploring health consequences of Asthma-COPD overlap syndrome in a national study
Pathway | Effect Size (95% CI)ᵃ | % of Total Effectᵇ | P-value | Bootstrap 95% CI |
|---|---|---|---|---|
Model 1: Smoking → BMI → ACOS | ||||
Total effect (c) | 0.582 (0.564–0.600) | 100% | <0.001 | 0.563–0.601 |
Direct effect (c’) | 0.486 (0.467–0.505) | 83.5% | <0.001 | 0.466–0.506 |
Indirect effect (a×b) | 0.096 (0.084–0.108) | 16.5% | <0.001 | 0.082–0.110 |
Proportion mediated | – | 16.5% | – | 14.5%–18.9% |
Model 2: Smoking → Depression → ACOS | ||||
Total effect (c) | 0.582 (0.564–0.600) | 100% | <0.001 | 0.563–0.601 |
Direct effect (c’) | 0.458 (0.439–0.477) | 78.7% | <0.001 | 0.438–0.478 |
Indirect effect (a×b) | 0.124 (0.109–0.139) | 21.3% | <0.001 | 0.107–0.141 |
Proportion mediated | – | 21.3% | – | 19.0%–24.2% |
Model 3: Smoking → Physical activity → ACOS | ||||
Total effect (c) | 0.582 (0.564–0.600) | 100% | <0.001 | 0.563–0.601 |
Direct effect (c’) | 0.524 (0.505–0.543) | 90.0% | <0.001 | 0.504–0.544 |
Indirect effect (a×b) | 0.058 (0.048–0.068) | 10.0% | <0.001 | 0.046–0.070 |
Proportion mediated | – | 10.0% | – | 8.2%–11.9% |
Multiple mediator model: Smoking → [BMI / Depression / Activity] → ACOS | ||||
Total effect | 0.582 (0.564–0.600) | 100% | <0.001 | 0.563–0.601 |
Direct effect | 0.364 (0.344–0.384) | 62.5% | <0.001 | 0.343–0.385 |
Total indirect effect | 0.218 (0.198–0.238) | 37.5% | <0.001 | 0.196–0.240 |
Via BMI | 0.082 (0.071–0.093) | 14.1% | <0.001 | 0.069–0.095 |
Via depression | 0.105 (0.092–0.118) | 18.0% | <0.001 | 0.090–0.120 |
Via physical activity | 0.031 (0.024–0.038) | 5.3% | <0.001 | 0.022–0.040 |
Total proportion mediated | – | 37.5% | – | 34.2%–41.1% |
