Smoking Cessation Attempts and Common Strategies Employed
A Germany-wide representative survey conducted in 19 waves from 2016 to 2019 (The DEBRA Study) and analyzed by socioeconomic status
Background: Clinical guidelines on smoking cessation contain recommendations for various evidence-based methods. The goal of this study was to provide a representative analysis for Germany of the percentage of smokers who try to quit smoking at least once per year, the use of evidence-based methods and other methods of smoking cessation, and potential associations of the use of such methods with the degree of tobacco dependence and with socioeconomic features.
Methods: Data from 19 waves of the German Smoking Behavior Questionnaire (Deutsche Befragung zum Rauchverhalten, DEBRA), from the time period June/July 2016 to June/July 2019, were analyzed. Current smokers and recent ex-smokers (<12 months without smoking) were asked about their smoking cessation attempts in the past year and the methods they used during the last attempt (naming more than one method was permitted). The degree of tobacco dependence in current smokers was assessed with the Heaviness of Smoking Index.
Results: Out of 11 109 current smokers and 407 recent ex-smokers, 19.9% (95% confidence interval: [19.1; 20.6]) had tried to quit smoking at least once in the preceding year. 13.0% of them [11.6; 14.5] had used at least one evidence-based method during their last attempt. The stronger the tobacco dependence, the more likely the use of an evidence-based method (odds ratio [OR] = 1.27 [1.16; 1.40]). Pharmacotherapy (nicotine replacement therapy, medication) was used more commonly by persons with higher incomes (OR = 1.44 per 1000 euro/month [1.28; 1.62]). Electronic cigarettes were the most commonly used single type of smoking cessation support (10.2 % [9.0; 11.6]).
Conclusion: In Germany, only one in five smokers tries to quit smoking at least once per year. Such attempts are only rarely supported by evidence-based methods and are thus likely to fail. The high cost of treatment must be borne by the individual and thus fall disproportionately on poorer smokers. It follows that there is an urgent need for evidence-based smoking cessation therapy to be covered by health insurance providers, in order to give all smokers fair and equal access to the medical care they need.
OAlthough smoking tobacco is the greatest avoidable risk factor for a multitude of diseases (1, 2), 28% of the population in Germany still smokes (3). Smokers are at risk of dying prematurely (on average 10 years earlier than non-smokers) as a result of tobacco consumption (4). In Germany, this affects 125 000 people per year. (5). From middle age, smokers lose about three months of their lifespan for every additional year of tobacco consumption (4). For this reason it is of vital importance for smokers to stop smoking as early as possible, completely, and permanently.
The crucial perpetuating factors for regular tobacco consumption are on the one hand operant and classic conditioning processes that affect behavior. On the other hand, they include the effects of nicotine on the dopaminergic, serotonergic, and noradrenergic transmitter systems—among others—as well as neuroadaptation in the sense of upregulation of the nicotinic acetylcholine receptor (also known as the alpha-4 beta-2 nicotinic receptor), which—among others—is also assumed to be associated with the vegetative withdrawal symptoms (6).
During the first two or more weeks of a quit attempt, smokers experience withdrawal symptoms, with increased irritability, aggressiveness, and edginess. Subjectively they suffer from reduced concentration, disturbed sleep, and a compulsory craving for smoking (7, 8). Unassisted smoking cessation attempts end unsuccessfully within 12 months in 95% of cases. Easy availability of tobacco and a low tolerance threshold regarding withdrawal symptoms—which are experienced as aversive—facilitate an early reuptake of smoking after cessation. A low expectation of coping and a high degree of negative affect are negative predictors for successful smoking cessation (9). Poor socioeconomic conditions reduce the chances of successful smoking cessation, probably in the context of a higher prevalence of smoking in this social group (10, 11).
The German S3 clinical practice guidelines (12, 13) recommend psychotherapeutic and pharmacological support for smoking cessation. This includes personal advice or behavioral counseling—such as brief physician advice, telephone counseling, or intensive behavioral therapeutic individual or group therapy—on the one hand, and pharmacotherapeutic support on the other hand. For the latter, the following nicotine replacement therapies are licensed in Germany: nicotine patches, chewing gum, inhalers, oral spray, or lozenges, as well as the medications varenicline and bupropion. A combination of both components—pharmacotherapy and behavioral interventions—is most effective in supporting smoking cessation (14); for example, in a recent randomized trial under routine care conditions (15), abstinence rates of more than 25% after 12 months were achieved in smokers managed in primary care practices. Numerous additional strategies are also used by smokers to assist them in their quit attempt, but the evidence for the effectiveness of these is not clear—such as acupuncture, diverse internet-based counseling services, and apps. Smokers also use electronic cigarettes (e-cigarettes) to support their quit attempt (1).
It is well known that smokers will make use of evidence-based smoking cessation treatment more commonly and more successfully if the costs are reimbursed (16–18). One explanation is that it is more commonly people on lower incomes who smoke—which also holds true for Germany (1, 19, 20). Unfortunately, treatment costs are not at all, or only partially, reimbursed in Germany (21). Participation in group therapy is subsidized only by some health insurance providers in the sense of a preventive measure, but smokers will have to cover pharmacotherapy all by themselves—even patients with chronic obstructive pulmonary disease, in the context of their disease management program (22).
No current representative data are available on the rates of smokers who try to stop smoking every year, which smoking cessation methods they use, and whether sociodemographic characteristics are associated with this use. The latest larger study is from 2012 (23); it showed that 24% of smokers at the time had made at least one attempt to give up smoking in the preceding 12 months (11% had used nicotine replacement, 5% had received counseling from their doctor, and 8% had used e-cigarettes) (23). Representative data on the status quo and an analysis of trends (with the study method remaining the same) would be important as indicators of the need and effectiveness of public health promotion and political tobacco control measures (such as increases in tobacco taxation).
This study therefore aimed to collect data on:
- The rate of smokers in Germany who made at least one attempt to give up smoking within the preceding year, on average as well as over the course of recent years
- The use of evidence-based methods and other strategies to support these attempts
- Possible associations between using such methods and the degree of tobacco dependency, as well as socioeconomic characteristics.
The data source was the DEBRA study (the German Study on Tobacco Use, www.debra-study.info) (24).
The DEBRA study was approved by the medical ethics committee of Heinrich Heine-University (HHU) Düsseldorf (ID 5386/R), registered (DRKS00011322), and extensively described in a study protocol (24). In sum, DEBRA is a representative, nationwide, computer-assisted, face-to-face household survey of persons aged 14 or older, who answer general sociodemographic questions as well as questions about smoking behavior. Every other month, a new representative sample of approximately 2000 persons is interviewed in the context of the survey covering several topics. The survey participants are selected by means of multistage, multi-stratified random probability sampling (see study protocol ) for details). The survey is being conducted by the market research institute Kantar on behalf of the Institute of General Practice at the HHU. In this article, we present weighted baseline data of the initial three years (19 waves) (June/July 2016 through June/July 2019).
Measuring attempts to quit smoking and withdrawal methods
Current smokers and recent ex-smokers (persons who stopped smoking completely within the preceding 12 months) were asked whether they had undertaken one or more attempts to quit smoking in the preceding 12 months. Persons who had made at least one such attempt were presented with a list of cessation methods and asked to select all methods they themselves had employed during the latest attempt (multiple selections allowed). Two further questions were asked in connection with this smoking cessation attempt:
- Was smoking reduced before quitting altogether or was it abruptly stopped?
- Was the attempt planned or spontaneous?
Furthermore, current smokers were asked how many cigarettes they smoked per day and how soon after waking up in the morning they smoked their first cigarette. These two responses constitute the Heaviness of Smoking Index (HSI, range from 0 to 6 = highest degree of tobacco dependency) (25), which is regarded as an indicator of the degree of tobacco dependency (>4 points = high dependency [26, 27]). The e-Questionnaire provides the precise wording of these questions (translated from the original German). Questions that are asked by default as part of the omnibus survey (age, sex, highest school leaving certificate/diploma, and net household income) are not listed.
Some data in this article are presented weighted in order to be able to draw conclusions about the prevalence in the population of Germany (weighted data are indicated with “nw”). Details about the weighting of the data are described in the study protocol (24).
For the association of socioeconomic characteristics and the use of evidence-based smoking cessations methods we calculated three multivariable logistic regression models, with different dependent variables:
- Use of any evidence-based method (I)
- Use of any evidence-based form of advice or behavioral therapy (II)
- Use of any evidence-based form of pharmacotherapy (III).
The independent variables that were included were:
- Education (as an ordinal variable with five categories)
- Net household income per capita (as a metric variable with 12 tiers equivalent to €1000 per tier)
- Heaviness of smoking index (HSI)
- Survey wave.
In calculating the net household income per capita, the number of persons in a household was weighted according to their need, in accordance with a recommendation from the Organization for Economic Cooperation and Development (OECD) (28) (details of the calculation are recoded in the Open Science Framework ). Since the HSI is calculated—among others—from the number of cigarettes smoked per day, it can be calculated only for current smokers. Recent ex-smokers (3.5% of the proportion of the total sample) were therefore excluded from these analyses.
For the individual analyses we used the data available in each case; persons with missing values were not included in the relevant analysis. Since the study is a face-to-face survey, the overall proportion of missing data is very small (in most questions below 1–2%) and can be explained with the simple fact that those surveyed did not want to or were not able to respond.
A total of 38 751 persons participated in the surveys. Of the 11 109 current smokers and 407 recent ex-smokers, 10 915 (nw=10 918 weighted) responded to the question about their attempts to stop smoking in the preceding 12 months (n = 601; 5.2%, not available).
In the total aggregated observation period (nw=10 918), 80.1%w of the respondents had not attempted to stop smoking (nw = 8748; 95% confidence interval [79.3; 80.8]) and 19.9%w (nw = 2169; [19.1; 20.6]) had made at least one such attempt (12.8%w), 4.2%g two attempts, 1.4%w three attempts, 1.5%w for our more attempts; all data are weighted.
Of the nw= 2169 smokers and recent ex-smokers who had made at least one attempt to give up smoking, 66.0%w (nw= 1.432; [64.0; 68.0]) had abruptly stopped smoking at their latest attempt, and 32.4%w (nw=702; [30.4; 34.4]) had reduced their consumption before stopping altogether (1.6%w; nw=35 not available). Furthermore, 57.3%w (nw=1242; [55.1; 59.4]) had stopped smoking spontaneously, and 39.8%w (nw=864; [37.8; 41.9]) had planned their quit attempt (2.9%w; nw=64, not available, all data weighted).
The Figure shows the time trend in the smoking cessation rate over the observation period (that is, at least one quit attempt in the preceding 12 months). After a rise in the first three survey waves to 33.9% in October/November 2016, the attempt rate dropped and was only 15.8% in the latest survey wave (June/July 2019; all data weighted).
Table 1 shows the weighted frequency of use of various methods to support the latest attempt to stop smoking in current smokers and recent ex-smokers, who had attempted to stop smoking in the preceding 12 months (weighted data). From the list of available methods (Table 1, e-Questionnaire; multiple selections allowed), 73.1%w (nw = 1585) had selected one method, 15.3%w (nw = 332) had selected two methods, 7.5%w (nw = 163) had selected three methods, and 4.1%w (nw = 89) had selected four or more methods). Nicotine replacement therapy was the relatively most commonly used single, evidence-based, method, with or without prescription (7.6%w; nw = 164), followed by brief physician advice (5.3%w; nw = 116). The relatively most often used, single, non–evidence-based cessation strategy was the e-cigarette, with a total of 10.2%w (nw = 222), of which 4.3%w (nw = 93) exclusively e-cigarettes containing nicotine, 4.8%g (nw = 104) exclusively e-cigarettes not containing nicotine, and 1.1%w (nw = 24) simultaneously e-cigarettes with and without nicotine.
13.0%w (nw = 282; [11.6; 14.5]) of smokers and recent ex-smokers had used at least one evidence-based method during their latest cessation attempt (Table 1); 6.9%w (nw = 150; [5.9; 8.1]) at least one form of advice or behavioral therapy; 8.2%w (nw = 177; [7.0; 9.4]) at least one form of pharmacotherapy; and 2.1%w (nw = 45; [1.5; 2.8]) a combination of a form of advice/behavioral therapy and pharmacotherapy (weighted data).
Table 2 shows the association between the degree of tobacco dependency, socioeconomic characteristics, and the use of evidence-based methods to support the latest attempt to stop smoking in current smokers. 17.2%w of current smokers (nw = 298) reported a high degree of tobacco dependency (16.1%w of female smokers and 18.2%w of male smokers). The use of a form of advice or behavioral therapy (odds ratio [OR] = 1.16 per point on the HSI scale [1.02; 1.30]), and also—to a greater extent—the use of a form of pharmacotherapy (OR = 1.44 [1.28; 1.62]) were associated with the degree of tobacco dependency. Furthermore, pharmacotherapy was used more frequently with increasing net household income per capita (OR = 1.34 per €1000 [1.07; 1.68]. Evidence-based methods were used more frequently with increasing age (OR = 1.01; [1.00; 1.02]). According to our data, associations with sex and level of education were less likely.
Smoking cessation is of vital importance in view of the devastating health effects of tobacco consumption. In spite of this, our data show that at best 19% of smokers in Germany make an attempt in a year to stop smoking. In an earlier survey of 2012, the rate was 24% (23), and over the observation period of our study (2016–2019) the rate fell even further, to 15% at the end.
The proportion of smokers who attempt to give up smoking has thus fallen in recent years. A similar trend has been observed in England (30, 31). Only 13% of smokers in Germany used an evidence-based method in their attempt to quit. In England, an earlier study found a rate of 51% (32). Pharmacotherapy is also used much more commonly in aiding tobacco cessation in England: in 48% of attempts, compared with 8% in Germany (32). In the Netherlands, 24% of primary care physicians prescribe pharmacotherapy in the context of smoking cessation counseling (33). In Germany, only 2% of smokers report having been given such a recommendation by their primary care physician (34). An important reason for these differences probably lies in the fact that the treatment costs for smoking cessation in England and in the Netherlands are reimbursed. In Germany, health insurers do not cover the costs of nicotine replacement therapies and medications, and smokers with lower incomes consequently cannot afford these. Since people on lower incomes smoke relatively more commonly than those on higher incomes (1, 19, 20), this state of affairs deserves a critical look, because as a result, the social gradient in the population’s health increases further. Cost reimbursement on the other hand could lead to physicians advising their patients more frequently and supporting them in giving up smoking than is currently the case (34).
We found an association between the degree of tobacco dependence and the use of evidence-based advice/behavioral therapy and pharmacotherapy. The rate of smokers in Germany with a high degree of tobacco dependency (17% with HSI >4) is below the European average (21%) (35). A study conducted in Germany in the early 21st century found that smokers with a higher tobacco consumption and higher nicotine dependence attempted to give up smoking more often (36). An English study showed—much like our own study—that attempts to stop smoking are more commonly supported with evidence-based advice/behavioral therapy and pharmacotherapy with increasing degree of tobacco dependence (32). This can be explained with the fact that smokers with a higher degree of dependency and associated withdrawal symptoms experience greater difficulties in giving up smoking by their own efforts and therefore seek help more readily.
The present study is subject to some methodological limitations. The method employed by the market research institute does not allow for calculating the response rate. All data in this study are based on participants’ self-assessments. Asking for smoking cessation attempts in the preceding 12 months and the cessation methods used may give rise to recall bias because participants may have forgotten cessation attempts that were only short-lived (37). It is also known that attempts using pharmacotherapy are remembered to a greater extent than unassisted attempts (38). The result of both of these factors may be that the attempt rate of 19% in a year was estimated too low.
As far as the evaluation of the information on the use of different cessation methods is concerned, an important limitation lies in the fact that our data do not include any information on adherence.
A final issue relates to the analysis of the association between characteristics of smokers and their use of different evidence-based cessation methods. Such an analysis can usefully only be undertaken while taking tobacco dependency into account, in order to prevent confounding. To this end, we used the HSI, whose shortcoming is, however, that it uses the number of cigarettes smoked per day as input values; we therefore had to exclude recent ex-smokers from our analysis. This group was small, however (n = 407), compared with current smokers (n = 11 109), and it is not plausible that their response behavior should be very different. For this reason we can exclude any relevant bias of the results.
In Germany, the rate of smokers who attempt to stop smoking is falling, and smoking cessation attempts are only too rarely supported with evidence-based methods. Efforts are therefore needed to reduce the continuing high tobacco consumption in Germany. Smokers need to receive better information via well-publicized measures and in the context of medical care about the advantages and available options for tobacco cessation, and evidence-based methods for this purpose should be easily accessible, nationwide, and free of charge.
We thank Kantar Health (Constanze Cholmakow-Bodechtel and Linda Scharf) for collecting the data.
The DEBRA study was funded from 2016 to 2019 by the Ministry of Innovation, Science and Research of the German State of North Rhine–Westphalia (MIWF) in the context of the “NRW Rückkehrprogramm” [the NRW postdoc return program]. Since 2019, the study has been funded by the German Federal Ministry of Health.
Conflict of interest statement
Prof Kotz is the elected representative of the German Society for General Practice and Family Medicine involved in updating the S3 clinical practice guideline “Screening, Diagnostics, and Treatment of Harmful and Addictive Tobacco Use” (AWMF registry No 076–006).
Prof Batra has received funding from Pfizer into a third-party account. He is a behavioral therapist and has developed his own tobacco withdrawal program (“non-smoker in 6 weeks”). He is the coordinator and director of the named S3 guideline “Screening, Diagnostics, and Treatment of Harmful and Addictive Tobacco Use”.
Dr. Kastaun declares that no conflict of interest exists.
Manuscript received on 11 June 2019, revised version accepted on 10 October 2019.
Translated from the original German by Birte Twisselmann, PhD.
Prof. Dr. Daniel Kotz, PhD MSc MPH
Institut für Allgemeinmedizin
Schwerpunkt Suchtforschung und klinische Epidemiologie
Medizinische Fakultät der Heinrich-Heine-Universität Düsseldorf
Postfach 101007, 40001 Düsseldorf
Cite this as:
Kotz D, Batra A, Kastaun S: Smoking cessation attempts and common strategies employed—a Germany-wide representative survey conducted in 19 waves from 2016 to 2019 (The DEBRA Study) and analyzed by socioeconomic status.
Dtsch Arztebl Int 2020; 117: 7–13. DOI: 10.3238/arztebl.2020.0007
Research Department of Behavioural Science and Health, Institute of Epidemiology and Health Care, University College London, London, UK: Prof. Dr. Daniel Kotz, PhD MSc MPH
Section for Addiction Medicine and Addiction Research, Department of Psychiatry and Psychotherapy, University Hospital and Faculty of Medicine, Tübingen: Prof. Dr. med. Anil Batra
|1.||Jha P, Ramasundarahettige C, Landsman V, et al.: 21st-century hazards of smoking and benefits of cessation in the United States. New Engl J Med 2013; 368: 341–50 CrossRef MEDLINE|
|2.||Mons U: Tobacco-attributable mortality in Germany and in the German Federal States—calculations with data from a microcensus and mortality statistics. Gesundheitswesen 2011; 73: 238–46.|
|3.||Kotz D, Böckmann M, Kastaun S: The use of tobacco, e-cigarettes, and methods to quit smoking in Germany—a representative study using 6 waves of data over 12 months (the DEBRA study). Dtsch Arztebl Int 2018; 115: 235–42 VOLLTEXT|
|4.||Doll R, Peto R, Boreham J, Sutherland I: Mortality in relation to smoking: 50 years‘ observations on male British doctors. BMJ 2004; 328: 1519–27 CrossRef MEDLINE PubMed Central|
|5.||Mons U, Brenner H: Demographic ageing and the evolution of smoking-attributable mortality: the example of Germany. Tob Control 2017; 26: 455–7 CrossRef MEDLINE|
|6.||Schmidt HD, Rupprecht LE, Addy NA: Neurobiological and neurophysiological mechanisms underlying nicotine seeking and smoking relapse. Mol Neuropsychiatry 2018; 4: 169–89 CrossRef MEDLINE|
|7.||Shiffman S, Patten C, Gwaltney C, et al.: Natural history of nicotine withdrawal. Addiction 2006; 101: 1822–32 CrossRef MEDLINE|
|8.||Piasecki TM, Jorenby DE, Smith SS, Fiore MC, Baker TB: Smoking withdrawal dynamics: I. Abstinence distress in lapsers and abstainers. J Abnorm Psychol 2003; 112: 3–13 CrossRef MEDLINE|
|9.||Aguirre CG, Madrid J, Leventhal AM: Tobacco withdrawal symptoms mediate motivation to reinstate smoking during abstinence. J Abnorm Psychol 2015; 124: 623–34 CrossRef MEDLINE PubMed Central|
|10.||Kotz D, West R: Explaining the social gradient in smoking cessation: It‘s not in the trying, but in the succeeding. Tob Control 2009; 18: 43–6 CrossRef MEDLINE|
|11.||Heilert D, Kaul A: [Smoking behaviour in Germany—evidence from the SOEP. SOEPpapers on Multidisciplinary Panel Data Research]. Berlin: DIW 2017. www.diw.de/documents/publikationen/73/diw_01.c.563343.de/diw_sp0920.pdf (last accessed on 27 November 2017).|
|12.||Batra A, Mann K: S3-Leitlinie „Screening, Diagnostik und Behandlung des schädlichen und abhängigen Tabakkonsums”. AWMF-Register Nr. 076–006. Düsseldorf: Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF) 2015 CrossRef|
|13.||Andreas S, Batra A, Behr J, et al.: [Smoking cessation in patients with COPD]. S3-Guideline issued by the German Respiratory Society]. Pneumologie 2014; 68: 237–58 CrossRef MEDLINE|
|14.||Stead Lindsay F, Lancaster T: Combined pharmacotherapy and behavioural interventions for smoking cessation. Cochrane Database Syst Rev 2012; 10: CD008286 CrossRef|
|15.||van Rossem C, Spigt M, Viechtbauer W, Lucas AEM, van Schayck OCP, Kotz D: Effectiveness of intensive practice nurse counselling versus brief general practitioner advice, both combined with varenicline, for smoking cessation: a randomized pragmatic trial in primary care. Addiction (Abingdon, England) 2017; 112: 2237–47 CrossRef MEDLINE|
|16.||van den Brand FA, Nagelhout GE, Reda AA, et al.: Healthcare financing systems for increasing the use of tobacco dependence treatment. Cochrane Database Syst Rev 2017; 9: CD004305 CrossRef MEDLINE PubMed Central|
|17.||Kaper J, Wagena EJ, Willemsen MC, van Schayck CP: Reimbursement for smoking cessation treatment may double the abstinence rate: results of a randomized trial. Addiction 2005; 100: 1012–20 CrossRef MEDLINE|
|18.||Kaper J, Wagena EJ, Willemsen MC, van Schayck CP: A randomized controlled trial to assess the effects of reimbursing the costs of smoking cessation therapy on sustained abstinence. Addiction 2006; 101: 1656–61 CrossRef MEDLINE|
|19.||Kuntz B, Zeiher J, Hoebel J, Lampert T: Soziale Ungleichheit, Rauchen und Gesundheit. Suchttherapie 2016; 17: 115–23 CrossRef|
|20.||Kuntz B, Kroll LE, Hoebel J, et al.: [Time trends of occupational differences in smoking behaviour of employed men and women in Germany : Results of the 1999–2013 microcensus]. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz. 2018; 61: 1388–98 CrossRef MEDLINE|
|21.||Lenzen-Schulte M: Tabakentwöhnung: Raucher schaffen es nicht allein. Dtsch Arztebl 2018; 115: A-1436–7 VOLLTEXT|
|22.||Gemeinsamer Bundesausschuss: Richtlinie des Gemeinsamen Bundesausschusses zur Zusammenführung der Anforderungen an strukturierte Behandlungsprogramme nach § 137f Absatz 2 SGB V (DMP-Anforderungen-Richtlinie/DMP-A-RL). Bundesanzeiger (BAnz AT 22 März 2019 B5) 2019.|
|23.||Kröger CB, Gomes de Matos E, Piontek D, Wenig JR: [Quitting attempts and utilisation of smoking cessation aids among smokers in Germany: results from the 2012 epidemiological survey of substance abuse]. Gesundheitswesen 2016; 78: 752–8 CrossRef MEDLINE|
|24.||Kastaun S, Brown J, Brose LS, et al.: Study protocol of the German Study on Tobacco Use (DEBRA): a national household survey of smoking behaviour and cessation. BMC Public Health 2017; 17: 378 CrossRef MEDLINE PubMed Central|
|25.||Heatherton TF, Kozlowski LT, Frecker RC, Rickert W, Robinson J: Measuring the heaviness of smoking: using self-reported time to the first cigarette of the day and number of cigarettes smoked per day. Br J Addict 1989; 84: 791–9 CrossRef MEDLINE|
|26.||de Leon J, Diaz FJ, Becoña E, Gurpegui M, Jurado D, Gonzalez-Pinto A: Exploring brief measures of nicotine dependence for epidemiological surveys. Addic Behav 2003; 28: 1481–6 CrossRef|
|27.||Chabrol H, Niezborala M, Chastan E, de Leon J: Comparison of the Heavy Smoking Index and of the Fagerstrom Test for Nicotine Dependence in a sample of 749 cigarette smokers. Addict Behav 2005; 30: 1474–7 CrossRef MEDLINE|
|28.||Organisation for Economic Co-operation and Development (OECD): Framework for integrated analysis. OECD Framework for statistics on the distribution of household income, consumption and wealth 2013. www.doi.org/10.1787/9789264194830-en (last accessed on 14 July 2019).|
|29.||DEBRA (the German Study on Tobacco Use): Materials of the DEBRA study. www.//osf.io/e2nqr/ (last accessed on 27 September 2019).|
|30.||West R, Mohr G, Proudfoot H, Brown J: Top-line findings on smoking in England from the Smoking Toolkit Study. www.smokinginengland.info (last accessed on 19 September 2019).|
|31.||Beard E, Jackson SE, West R, Kuipers MAG, Brown J: Trends in attempts to quit smoking in England since 2007: a time series analysis of a range of population-evel influences. Nicotine Tob Res 2019; pii: ntz141. doi: 10.1093/ntr/ntz141 [Epub ahead of print] CrossRef MEDLINE|
|32.||Kotz D, Fidler J, West R: Factors associated with the use of aids to cessation in English smokers. Addiction 2009; 104: 1403–10 CrossRef MEDLINE|
|33.||Kotz D, Willemsen M, Brown J, West R: Light smokers are less likely to receive advice to quit from their GP than moderate-to-heavy smokers: a comparison of national survey data from the Netherlands and England. Eur J Gen Pract 2013; 19: 99–105 CrossRef MEDLINE|
|34.||Kastaun S, Kotz D: [Brief physician advice for smoking cssation: results of the DEBRA study]. SUCHT 2019; 65: 34–41 CrossRef|
|35.||Fernández E, Lugo A, Clancy L, Matsuo K, La Vecchia C, Gallus S: Smoking dependence in 18 European countries: hard to maintain the hardening hypothesis. Prev Med 2015; 81: 314–9 CrossRef MEDLINE|
|36.||John U, Meyer C, Hapke U, Rumpf H-J, Schumann A: Nicotine dependence, quit attempts, and quitting among smokers in a regional population sample from a country with a high prevalence of tobacco smoking. Prev Med 2004; 38: 350–8 CrossRef MEDLINE|
|37.||Berg CJ, An LC, Kirch M, et al.: Failure to report attempts to quit smoking. Addict Behav 2010; 35: 900–4 CrossRef MEDLINE|
|38.||Borland R, Partos TR, Cummings KM: Systematic biases in cross-sectional community studies may underestimate the effectiveness of stop-smoking medications. Nicotine Tob Res 2012; 14: 1483–7 CrossRef MEDLINE PubMed Central|