We read with interest the paper by Fagerström & Furberg published recently in Addiction. The authors' hypothesis is appealing: smokers remaining in populations where the prevalence of smoking has decreased are hardening. The data indicate an inverse relationship between smoking prevalence and nicotine dependence, assessed by the Fagerström Test for Nicotine Dependence (FTND) .
The data presented by Fagerström & Furberg derive from population-based cross-sectional studies conducted in different European countries and the United States during the last two decades. With regard to the Spanish data, the study used by Fagerström & Furberg was from a cross-sectional survey conducted in 1997 in Galicia [3,4], a region in the North West of Spain with approximately 7.5% of the Spanish population.
Since 1997, however, the prevalence of smoking has decreased in Spain [5,6]. We present recent prevalence rates and nicotine dependence levels in the whole Spanish population to address further the ‘hardening hypothesis’. These data were not available to Fagerström & Furberg at the time they conducted their study.
We conducted a cross-sectional survey of a representative sample of the Spanish population aged ≥ 18 years to assess active and passive smoking at the population level. The sample was representative in terms of sex, age, municipality and region, and substitution by people of the same strata was allowed. Hence, we obtained valid responses from 2522 participants (1221 men and 1301 women). Data were collected in June and July 2006 by trained interviewers with a structured questionnaire using a computer-assisted telephone interview. As well as basic socio-demographic data, the questionnaire gathered information on smoking habits, including the FTND for current smokers, on perceived exposure to second-hand smoke for non-smokers, and about knowledge and attitudes of both active and passive smoking. Details of the methods and results on exposure to second-hand smoke are available elsewhere .
Results indicate that 23.4% of Spanish adults were daily cigarette smokers (27.0% of men, 20.1% of women, P < 0.05). The mean FTND score was 2.8 (3.0 in men and 2.5 in women, P < 0.05). This different level of dependence according to sex is due mainly to the difference in the mean number of cigarettes smoked per day by men (15.7) and women (12.8, P < 0.05). Overall, smokers reported smoking 14.4 cigarettes daily. The data indicate a decrease in smoking prevalence but not an increase in nicotine dependence, as also observed in Italy . Apparently, the reduction of the prevalence without a substantial change in dependence would go against the generalization of the hardening hypothesis.
In addition to ecological studies including different countries as the unit of analysis , trends of smoking prevalence and FTND scores across time within countries should be analysed in repeated and comparable cross-sectional surveys to understand further the dynamics and determinants of nicotine dependence at the population level.