Toward a More Comprehensive Index of Youth Cigarette Smoking: Average Number of Cigarettes Smoked per Day among Students in the United States over Two Decades.

Reliance on 30-day prevalence as the principal means of assessing trends in youth cigarette smoking may understate the magnitude of the decrease in youth smoking, because prevalence does not account for smoking frequency or intensity. We analyzed Youth Risk Behavior Survey (YRBS) data from 1997 through 2017 and estimated cigarette smoking prevalence (any smoking in the previous 30 days), frequency (number of smoking days in the previous 30 days), and intensity (cigarettes per day on smoking days). We calculated average cigarettes smoked per day (ACSD) as the product of frequency and intensity, divided by 30. We estimated ACSD among all high school students and by smoking frequency group (i.e., 1-5, 6-9, 10-19, 20-29, or 30 of the previous 30 days), sex, grade level, and race/ethnicity. Among US high school students, ACSD declined by 86.7% from 1997 to 2017, while prevalence declined by 75.8%. Within smoking frequency groups, smoking intensity remained similar over the two decades. However, changes in ACSD over time varied by race/ethnicity; ACSD increased among Hispanic and non-Hispanic Black daily smokers while it decreased among daily smokers of other race/ethnicity groups. ACSD declined more substantially than smoking prevalence over two decades but remained virtually unchanged within smoking frequency groups, indicating that changes in frequency, rather than intensity, drove this decline. Prevalence estimates alone understate the degree to which youth in the United States have rejected smoking, and racial/ethnic disparities in smoking intensity are hidden when we limit our lens to prevalence-only measures.