Smoking prevalence: a comparison of two American surveys.

ABSTRACT

OBJECTIVES: To compare smoking prevalence estimates from two nationally representative surveys in the USA. STUDY DESIGN: Smoking prevalence estimates derived from the National Health Interview Survey (NHIS) and the National Survey on Drug Use and Health (NSDUH) for the period 1998-2005. METHODS: Comparisons according to age (18-34 or 35+ years) and according to smoking frequency (every day or some days). RESULTS: In 1998, the prevalence of smoking in both surveys was nearly identical at 24%. From 1999 to 2005, a divergence occurred in smoking prevalence found by the NSDUH and the NHIS. By 2005, NHIS prevalence had declined to 20.9% [95% confidence interval (CI) 20.3-21.5], but the NSDUH estimate was 25.4% (95%CI 24.6-26.2), amounting to 9.1 million more smokers. In 1999, prevalence among 18-34 year olds in the NSDUH was only 18% (95%CI 13-22) higher than that in the NHIS, but that difference had doubled by 2005, when smoking prevalence among 18-34 year olds was 36% (95%CI 30-41) higher in the NSDUH than in the NHIS. NSDUH and NHIS prevalence among 35+ year olds were similar in 1999 and 2001, but the difference was 13% (95%CI 9-18) in 2005. Higher smoking prevalence estimates in the NSDUH were largely due to much higher estimates for some-day smoking in that survey, although every-day smoking prevalence among 18-34 year-olds was also higher in the NSDUH than in the NHIS. CONCLUSIONS: These results raise doubt about the recent decline in smoking prevalence described by the NHIS. Further investigation of the NSDUH/NHIS discrepancy may lead to better surveys and to a clearer picture of smoking trends in the USA.