From 1965 to 2007, the population prevalence of persons who smoked 20 or more cigarettes per day declined significantly, and there was also a decrease in the prevalence of smoking 10 or more cigarettes a day, with these declines greater in California than in the rest of the U.S., according to a study in the March 16 issue of JAMA. Throughout much of the early history of cigarette smoking in the United States, consumption was typically 1 pack (about 20 cigarettes) each day. Since the first surgeon general's report on smoking and health (1964), there has been a major decline in smoking prevalence. During this period, California has consistently led the United States in using public policies to reduce cigarette smoking, and there were faster declines in smoking prevalence in California compared with the remaining United States, as well as in lung cancer rates, according to background information in the article. "The intensity¹ of smoking [such as number of cigarettes smoked per day], not just prevalence, is associated with future health consequences," the authors write.

John P. Pierce, Ph.D., of the University of California San Diego, La Jolla, and colleagues examined trends in smoking intensity for both California and the remaining United States using two large population-based surveys with state estimates: National Health Interview Surveys, 1965-1994; and Current Population Survey Tobacco Supplements, 1992-2007. There were 139,176 total respondents for California and 1,662,353 for the remaining United States.

The researchers found that in 1965, the prevalence of high intensity (20 or more cigarettes per day) of smoking among California adults did not differ from the remaining United States; prevalence of high-intensity smoking in California was 23.2 percent compared with 22.9 percent in the remaining United States, and these smokers² represented 56 percent of all smokers. By 2007, this prevalence was 2.6 percent or 23 percent of smokers in California and 7.2 percent or 40 percent of smokers in the remaining United States.

The population prevalence of moderate-intensity smoking (10 or more cigarettes per day) in 1965 was 11.1 percent in California and 10.5 percent in the remaining United States; in 2007, the prevalence in California was 3.4 percent compared with 5.4 percent in the remaining United States.

"Among individuals (U.S. residents excluding California) born between 1920-1929, the prevalence of moderate/high-intensity smoking was 40.5 percent 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 percent in California and 18.3 percent 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 percent in California and 13.5 percent in the remaining United States," the authors write.

"The rapid decline in prevalence of 10 or more-cigarettes per day [CPD] smoking across birth cohorts in the mid-1960s is consistent with earlier reports of increased incidence of cessation that occurred following the dissemination³ of the early scientific reports that smoking caused cancer."

The researchers add that one of the reasons why the decline in moderate-intensity smoking has been greater in California than in the remaining United States is its comprehensive tobacco control programs.

The authors note that as expected, the large decline in the prevalence of pack-a-day smoking has been reflected in declines in lung cancer deaths in California and the U.S.

"In summary, over the past 40 years patterns of smoking have changed dramatically in the United States and reflect both reduced initiation⁴ and increased cessation," the researchers write. "Among younger birth cohorts, only a small minority of the population is expected to ever attain⁵ cigarette consumption levels of even 10 or more CPD. Further study of these changes in the intensity of smoking patterns should assess the relative importance of changes in initiation, cessation, and reduced consumption in the documented decline of health consequences of smoking in the United States."