Temporal changes of under-reporting of cigarette consumption in population-based studies

Objectives To monitor trends in under-reporting of smoking in Italy over the last two decades. Methods A total of 9 representative population-based surveys on smoking conducted in Italy in 1990 and annually between 2001 and 2008, covering 26 397 individuals, were studied. The number of cigarettes per day per person aged 15 years or over, obtained from these interview-based surveys, was compared with official data from legal sales. Results Over the last two decades, self-reported smoking prevalence progressively decreased from 32% in 1990 to 22% in 2008. Self-reported daily per capita consumption of cigarettes also showed a reduction between 1990 and 2008, notably so over the last few years (from 5.2 in 1990 to 4.0 in 2004 to 3.2 in 2008). According to data from legal sales, number of cigarettes per day per person decreased from 5.3 in 1990 to 5.0 in 1992, levelled off from 1992 to 1997, subsequently increased from 5.0 in 1997 to 5.8 in 2002 (likely due to control of smuggling), and decreased over the last 6 years (to 4.9 in 2008). These figures correspond to an under-reporting of approximately 1% in 1990, 25% in 2001 and up to 35% in 2008. Conclusions The difference in cigarette consumption between legal sale and self-reported data has substantially increased over the last two decades in Italy, reflecting increasing under-reporting of cigarette consumption mainly due to a decreasing social acceptability of smoking. Comparisons between interview-based and legal sale data are complicated by factors such as smuggling control and changes in the population (eg, increased proportion of immigrants); however these are able to justify only a small proportion of the gap found in Italy.