Data on tobacco smoking was collected during home interviews. Participants were asked about past and present cigarette, cigar and pipe smoking behaviour and were then categorized into current, former and never tobacco smokers. Furthermore, information on starting age of smoking, stopping age and time of discontinuation were used to determine packyears in current smokers (median 25.6 packyears, interquartile range 11.4 to 38.0) and cessation time in former smokers (median 21.5 years, interquartile range 10.6 to 32.6). Seven participants had missing smoking status and were therefore excluded from any analysis. During the centre visit, weight and height were measured in standing position wearing normal cloths. All participants had blood samples taken during the visit to quantify DNA methylation, messenger RNA (mRNA) expression levels and other blood measurements.
