Prevalence of Heavy Smoking in California and the United States, 1965-2007

Study Questions:

Have smoking intensity patterns changed over time?


Data from two large population-based surveys were used for the present analysis. Self-reported smoking patterns were assessed through the National Health Interview Surveys (1965-1994), and Current Population Survey Tobacco Supplements (1992-2007). A total of 139,176 adults residing in California and 1,662,353 respondents from the United States were included. The primary outcome of interest was number of cigarettes smoked per day. Respondents were also grouped into three categories: high-intensity smokers (defined as smoking ≥20 cigarettes/day), moderate-intensity smokers (10-19 cigarettes/day), and low-intensity smokers (0-9 cigarettes).


Smoking rates declined significantly over time. In 1965, 23.2% of adults in California (confidence interval [CI], 19.6%-26.8%) and 22.9% of adults in the remaining United States (95% CI, 22.1%-23.6%) were high-intensity smokers, representing 56% of all smokers. By 2007, this prevalence was 2.6% (95% CI, 0.0%-5.6%) or 23% of smokers in California, and 7.2% (95% CI, 6.4%-8.0%) or 40% of smokers in the remaining United States. Among individuals (US residents excluding California) born between 1920-1929, the prevalence of moderate/high-intensity smoking (≥10 cigarettes smoked per day) was 40.5% (95% CI, 38.3%-42.7%) in 1965. Moderate/high-intensity smoking declined across successive birth cohorts, and for the 1970-1979 birth cohort, the highest rate of moderate/high-intensity smoking was 9.7% (95% CI, 7.7%-11.7%) in California and 18.3% (95% CI, 16.4%-20.2%) in the remaining United States. There was a marked decline in moderate/high-intensity smoking at older ages in all cohorts, but this was greater in California. By age 35 years, the prevalence of moderate/high-intensity smoking in the 1970-1979 birth cohort was 4.6% (95% CI, 3.0%-6.1%) in California and 13.5% (95% CI, 11.8%-15.1%) in the remaining United States.


The investigators concluded that the number of high-intensity smokers has decreased significantly in the United States. The greater decline observed among Californians was most likely due to a reduction in people starting to smoke and a probable increase in smoking cessation.


This study suggests that the number of adults smoking 20 or more cigarettes per day has declined significantly without a concurrent increase in low to moderate smoking rates.

Clinical Topics: Prevention, Smoking

Keywords: Prevalence, Tobacco, California, Smoking Cessation, Smoking, United States

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