Table 2.
Results from our full Cox proportional hazards model for risk for drug abuse (DA) as a function of whether the DA-affected cousin was older versus younger
| Variable | HR (95% CI) | χ2, df=1 | p value |
|---|---|---|---|
| Older versus younger cousin | 1.42 (1.37–1.47) | 341.1 | <0.0001 |
| Older versus younger cousin × log(follow-up) | 1.18 (1.15–1.20) | 268.4 | <0.0001 |
| Age differences | 0.94 (0.93–0.94) | 923.0 | <0.0001 |
| Age differences × log(follow-up) | 1.03 (1.03–1.03) | 502.3 | <0.0001 |
| Gender | |||
| Male–male | Reference | ||
| Male–female | 0.35 (0.34–0.37) | 3017.4 | <0.0001 |
| Female–female | 0.41 (0.37–0.44) | 429.7 | <0.0001 |
| Female–male | 0.90 (0.85–0.96) | 11.5 | <0.0001 |
| Interaction terms | |||
| Older cousin × female–female | 0.85 (0.76–0.94) | 8.9 | 0.0029 |
| Older cousin × female–male | 0.92 (0.85–0.99) | 4.6 | 0.0322 |
HR, Hazard ratio; CI, confidence interval; df, degrees of freedom.