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.
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.
"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 dissemination of the early scientific reports that smoking caused cancer," the authors said.
The researchers added 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 study is published in the March 16 issue of JAMA.