Declining trend in cigarette smoking among U.S. adults over 2008-2018: A decomposition analysis.

The United States (U.S.) witnessed considerable reduction in cigarette smoking prevalence in the recent past. While the correlates of smoking prevalence and related disparities among U.S. adults are well documented, there is limited information on how this success was shared among different population sub-groups. Based on data from the National Health Interview Surveys, 2008 and 2018, representative of non-institutionalized U.S. adults (18 years and above), we applied the threefold Kitawaga-Oaxaca-Blinder linear decomposition analysis. We decomposed the trends in cigarette smoking prevalence, smoking initiation, and successful cessation into changes in population characteristics holding smoking propensities constant (compositional change), changes in smoking propensities by population characteristics holding population composition constant (structural change), and the unmeasured macro-level changes affecting smoking behavior in different population sub-groups at differential rates (residual change) to quantify the shares of population sub-groups by sex, age, race/ethnicity, education, marital status, employment status, health insurance coverage, family income, and region of residence in the overall change in smoking rates. The analysis shows that decreases in smoking propensities regardless of the changes in population composition accounted for 66.4% of the reduction in smoking prevalence and 88.7% of the reduction in smoking initiation. The major reductions in smoking propensity were among Medicaid recipients and young adults (ages 18-24 years). The 25-44-year-olds experienced moderate increase in successful smoking cessation, while the overall successful smoking cessation rate remained steady. Taken together, consistent reduction in smoking among U.S. adults by all major population characteristics, accompanied by disproportionately larger reduction in smoking propensities among the population sub-groups with initially higher smoking propensity compared to the national average, characterized the decline in overall cigarette smoking. Strengthening proven tobacco control measures with targeted interventions to reduce smoking propensities among underserved populations is key to continued success in reducing smoking overall and remedying inequities in smoking and population health.