Vol.2, No.3, 394-402 (2012) Open Journal of Preventive Medicine doi:10.4236/ojpm.2012.23057 Does a population-based multi-factorial lifestyle intervention increase social inequality in smoking? The Inter99 study Charlotta Pisinger 1* , Mette Aadahl 1 , Ulla Toft 1 , Anne Helms Andreasen 1 , Torben Jørgensen 1,2,3 1 Research Centre for Prevention and Health, Glostrup University Hospital, The Capital Region of Denmark, Copenhagen, Denmark; * Corresponding Author: charlotta.pisinger@regionh.dk 2 Faculty of Health Science, Copenhagen University, Copenhagen, Denmark 3 Faculty of Medicine, University of Aalborg, Aalborg, Denmark Received 20 February 2012; revised 28 March 2012; accepted 16 April 2012 ABSTRACT Introduction: The social inequality in smoking in the Western countries has been increasing. It has been suggested that the most important strategy to reduce health inequalities related to socio economic status (SEP) is to promote smok- ing cessation in persons with low SEP. One could fear that a smoking cessation intervention might benefit smokers with high SEP more, and thereby increase the social inequality in smok- ing. We wanted to investigate whether the effect differed across SEP. Methods: The study was an individual multi-factorial lifestyle intervention study with a control group, Inter99 (1999-2006), Copenhagen, Denmark. We included 1991 daily- smokers with self-reported information on edu- cation in the intervention group, and 1135 in the control group. Smokers in the intervention group were repeatedly offered individual lifestyle-coun- selling and group-based smoking cessation. We used generalised linear mixed models under the assumption of missing at random, including in- teraction term between intervention effect and SEP. Results: The gap in self-reported absti- nence rates increased over time between per- sons with high and low education. Probability of abstinence was significantly higher in the in- tervention group than in the control group, at all follow-up-visits but the effect of the intervention changed over time. The differences in quit-rates across educational groups were not signifi- cantly different in the intervention than in the control group at any time. Conclusion: In this randomised population-based intervention study we found that smokers across all educational levels benefited from the anti-smoking interven- tion, and that the intervention did not increase the social inequality in smoking, as one could have feared. Keywords: Smoking Cessation; Smoking; Socioeconomic Factors; Intervention Studies; Inter99 Study 1. INTRODUCTION Persons with low socioeconomic position (SEP) often have difficult living conditions making them susceptible to disease [1,2] and there is a strong association between population health and income inequality levels [3]. How- ever, a recently published study found that smoking is a greater source of health inequality than social position [4]. The study suggests that the most important strategy to reduce health inequalities related to social position is to promote smoking cessation in persons with low social position. The social inequality in smoking in the Western countries has been increasing in the last decades [5-9] and an English report (Securing good health for the whole population) concluded “We do not know what messages and interventions work to get lower socioeco- nomic groups to stop smoking” [10]. When planning strategies/interventions to reduce social inequalities in health, evidence of the effect of the strategy is needed before implementing it. In the worst case a strategy could have the opposite effect, and increase the social inequal- ity in smoking. A large Danish population-based multi-factorial inter- vention study, the Inter99 study, used a proactive ap- proach and an intensive, repeated lifestyle intervention over five years, resulting in significantly higher quit rates than in the control group [11]. The question is, whether smokers from all socioeconomic groups did benefit from Copyright © 2012 SciRes. Openly accessible at http://www.scirp.org/journal/ojpm/