摘要：Objectives. We estimated the long-term effects of smoking cessation interventions to inform government decision-making regarding investment in tobacco control. Methods. We extracted data from the 2006 New Zealand Tobacco Use Survey and other sources and developed a system dynamics model with the iThink computer simulation package. The model derived estimates of population cessation rates from smoking behaviors and applied these over a 50-year period, from 2001 to 2051, under business-as-usual and enhanced cessation intervention scenarios. Results. The model predicted larger effects by 2051 with the enhanced cessation than with the business-as-usual scenario, including: an 11% greater decline in adult current smoking prevalence (9 versus 10 per 100 people), 16% greater decline in per capita tobacco consumption (370 versus 440 cigarette equivalents per year), and 11% greater reduction in tobacco-attributable mortality (3000 versus 3300 deaths per year). Conclusions. The model generated reliable estimates of the effects on health and on tobacco use of interventions designed to enhance smoking cessation. These results informed a decision announced in May 2007 to increase funding for smoking cessation by NZ $42 million over 4 years. Tobacco use peaked in New Zealand around 1970. Smoking prevalence (daily plus nondaily) among adults has since declined from approximately 35% to 21%, and tobacco consumption has fallen from approximately 3000 cigarette equivalents per person-year to 1000. 1 For the past decade, smoking rates among youths have declined yearly across all social and ethnic groups. 2 Nevertheless, tobacco use remains the leading preventable cause of mortality, accounting for almost 1 in 5 deaths annually, or approximately 4200 from active smoking and 300 from secondhand smoke exposure in 2006. 1 Clearly, much remains to be done, but New Zealand already enjoys one of the world's most comprehensive tobacco control programs and is compliant with the mandates of the World Health Organization's Framework Convention on Tobacco Control, ratified in 2003. 3 New Zealand's tobacco control program comprises comprehensive legislation for smoke-free environments, including restaurants and bars; taxes on tobacco products amounting to approximately 70% of total price; a total advertising and sponsorship ban (although retail tobacco displays remain); a comprehensive countermarketing strategy, including regular media campaigns; and provision of smoking cessation services, including a national telephone quit line and heavily subsidized nicotine replacement therapy (NRT). 3 The tobacco control program is supported by a sophisticated monitoring program; since 2006, the government has conducted a dedicated annual population-based survey, the New Zealand Tobacco Use Survey (NZTUS). 4 The 2006 NZTUS estimated that 44% of smokers currently attempted to quit at least once each year, although at least 70% said they would like to quit. However, only 20% of quit attempts were assisted, usually with NRT and multisession behavioral support, 5 limiting the likelihood of long-term success. The survey thus identified smoking cessation as an outstanding opportunity for further improving tobacco control. A major increase in funding for cessation was announced by the government in its May 2007 budget. 6 Tobacco use and control can be thought of as a complex system containing emergent properties, feedback loops, and nonlinear dynamics. Traditional epidemiological methods deal with complexity by breaking the issue down into parts simple enough to be controlled (randomized controlled trials) or observed (cohort or case–control studies). System dynamics, by contrast, deals with complexity by abstracting the key elements of the system and simulating their dynamic interrelationships (with multiple differential equations) over time. 7 – 11 System dynamics is widely regarded as a suitable method for analyzing complex tobacco policy issues and complex public health issues in general. 12 Previous dynamic simulation studies related to tobacco policy include system dynamics modeling work at the Massachusetts Institute of Technology around 1980 on the effects of smoking 13 ; a Markovian computer simulation model developed in the United States for analyzing tobacco-related policies 14 – 18 ; SimSmoke, a computer simulation model that assesses the effects of a broad array of public policies related to tobacco control 19 , 20 ; dynamic modeling work at the University of Michigan related to US tobacco policy and smoking objectives 21 – 23 ; and a system dynamics study at the New Zealand Customs Service that analyzed public policy issues related to the collection of tobacco excise duties. 24 We estimated the health effects of enhanced cessation with the assistance of a system dynamics model, 25 developed to guide the New Zealand tobacco control community in the formulation and evaluation of the dynamic consequences of tobacco control policies.
