Table 4. Additive effects of (a) traumatic events, (b) neighborhood social cohesion and genetic risk on cigarette use in the Detroit Neighborhood Health Study.
| Environmental exposure | Genetic risk score | Cigarettes per day mean (95% CI)a |
|---|---|---|
| Traumatic life events | ||
| −1 s.d. (n=685) | −1 s.d. (n=195) | 10.91 (09.94,11.89) |
| +1 s.d. (n=58) | 11.22 (10.44,11.29) | |
| Differenceb | 0.31 (−0.50, 0.60) | |
| +1 s.d. (n=862) | −1 s.d. (n=295) | 10.98 (09.97,11.79) |
| +1 s.d. (n=102) | 12.20 (11.58,12.52) | |
| Differenceb | 1.22c (0.73, 1.61) | |
| Interaction contrastc | 0.91cd (0.23, 1.01) | |
| Neighborhood social cohesion | ||
| −1 s.d. (n=520) | −1 s.d. (n=171) | 09.48 (08.80, 10.56) |
| +1 s.d. (n=57) | 12.07 (11.88, 12.26) | |
| Differenceb | 2.59c (1.70, 3.08) | |
| +1 s.d. (n=1011) | −1 s.d. (n=317) | 10.14 (9.44, 11.23) |
| +1 s.d. (n=102) | 10.22 (9.47, 10.18) | |
| Differenceb | 0.08 (−1.85, 2.03) | |
| Interaction contrastd | 2.51c (1.05, 3.55) | |
a
Adjusted for age, sex and ancestry using overdispersed Poisson regression.
b
Difference between the mean for presence of high genetic risk versus low genetic risk, calculated on the mean (additive) scale using overdispersed Poisson regression with linear link function.
c
P-value <0.05.
d
Difference of the differences; additive interaction is indicated when the difference between the mean differences for the environmental exposure group versus the no-exposure group is significantly >0.