Table 3.
Cox proportional hazard regression survival analysis predicting days to heavy alcohol use with alcohol relapse as a censoring variable. Neutral-relaxed state adrenal sensitivity, as indicated by the cortisol: adrenocorticotropic hormone (cort: ACTH) ratio, increases risk of relapse, with a Hazard Ratio (HR) of 2.521 (p=0.0399, 95% confidence interval (CI) = 1.044–6.091). (b). The cort: ACTH ratio accounts for one third of the variance in Ventromedial Prefrontal Cortex (VmPFC) neutral state hyperactivation (R2 = 0.3364, p<0.001) and no longer significantly increases relapse risk when combined with VmPFC neutral state hyperactivation in a predictive model (HR= 1.875, p=0.2956, 95% CI=0.577–6.092). In this combined model, the neutral state VmPFC hyperactivation mediates the effect of high neutral-relaxed state cort: ACTH ratio on relapse risk, (HR=6.293, p=0.0197, 95% CI=1.341–29.531). N.B. We have previously demonstrated that neutral state VmPFC hyperactivation significantly increases risk of relapse, (HR= 9.739, p= 0.0011, 95% CI= 2.494–38.028) in Seo et al., 2013.
| Analysis of Maximum Likelihood Estimates | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Parameter | df | Parameter Estimate | Standard Error | Chi-Square | P | Hazard Ratio | 95% Hazard Ratio Confidence Limits | ||
| Model 1 | Neutral Cortisol: ACTH Ratio | 1 | 0.92479 | 0.45005 | 4.2224 | 0.0399 | 2.521 | 1.044 | 6.091 |
| Basal Heart Rate | 1 | −0.04224 | 0.02323 | 3.3073 | 0.069 | 0.959 | 0.916 | 1.003 | |
| Model 2 | Neutral Cortisol: ACTH Ratio | 1 | 0.62876 | 0.60111 | 1.0941 | 0.2956 | 1.875 | 0.577 | 6.092 |
| Neutral VmPFC Hyperreactivity | 1 | 1.83949 | 0.78877 | 5.4386 | 0.0197 | 6.293 | 1.341 | 29.531 | |
Note: df= degrees of freedom, Parameter Estimate= Beta value in equation of the line, p= p value of hazard ratio.