Within family transmission of secondhand smoke sensitivity and smoking attitude

Introduction and objective:
The role of genetic factors in nicotine dependence is well understood, but no information is available on the inheritability of second-hand smoke (SHS) exposure sensitivity and their co-variance.

Material and Methods:
186 adult same-gender pairs of twin (146 monozygotic, 40 dizygotic; 44±17 years±SD) completed a questionnaire.

Results:
The model showed a significant role of unshared environmental factors influencing the co-variance between smoking habit and SHS sensitivity (re=-0.191, 95% CI, -0.316 to -0.056, or the total phenotypic correlation of rph=-0.406, p<0.001) without evidence for genetic covariation. Age, gender and country-adjusted analysis indicated 51.5% heritability for smoking habit (95% confidence interval/CI/, 6.2 to 89.8%), 49.7% for SHS sensitivity (95%CI, 19.1–72.0%), 35.5% for general opinions on SHS exposure in restaurants/cafés (95%CI, 10.7–58.6%), and 16.9% in pubs/bars (95%CI, 0.0–49.0%).

Conclusions:
The co-variance between SHS sensitivity and smoking habits is driven mainly by the unshared environment. SHS sensitivity is moderately inheritable. The considerable influence of environmental factors on general opinions on SHS exposure in designated indoor public venues emphasizes the importance of smoking bans and health behaviour interventions at the individual level in developing an anti-smoking attitude.