The Australian component of the NAG project (Saccone et al. 2007), a collaboration between Queensland Institute of Medical Research (QIMR) and Washington University School of Medicine (WUSM) investigators, used data collection procedures approved by both institutions’ institutional review boards. Detailed descriptions of study methods have been reported (Saccone et al. 2007; Agrawal et al. 2008). In brief, prior reports by index cases of smoking status and family structure (in surveys of two large Australian Twin Panel cohorts and of spouses of the older twin cohort) were used to ascertain families with a sib pair [containing at most one monozygotic (MZ) twin] concordant for heavy smoking. Index cases were contacted to confirm smoking history and to obtain permission to contact family members. Families with two available parents were prioritized. When both parents were not available, at least one unaffected sibling was targeted for recruitment. After confirmation of family eligibility, study materials (including consent form) were mailed and telephone interviews scheduled with individual family members. Interviewing was conducted from 2001-2006. Data from only one member of any MZ twin pair, the designated index case, were included in analyses.
