An examination of smoking initiation rates by age: results from a large longitudinal study in New Zealand

Investigations of smoking initiation often focus on the experiences of children and youth. However, prevalence data from the Tobacco Use Surveys (TUS) and the New Zealand (NZ) census suggest substantial uptake of smoking occurs after 15 years of age, including among young adults aged 18-24 years. Identifying initiation rates is difficult using cross-sectional prevalence data, particularly among older age groups, which are subject to cohort effects and where quitting and premature mortality reduce prevalence. We aimed to identify initiation rates using a prospective study design.

The SoFIE-Health longitudinal survey included 15,095 subjects aged 15 years or older who responded in the three years that include the health module: 2004/05, 2006/07 and 2008/09. We calculated the proportion of 'never smokers' who became regular smokers (initiation) by age at baseline.

Initiation between 2004/05 and 2008/09 was 14.2% for 15-17 year olds, 7.0% for 18-19 years, 3.1% for 20-24 years and 1.4% for 25-34 years, with low levels of initiation (<1.0%) among older age groups.

There were strong age-related gradients in smoking initiation. Substantial initiation occurs among older youth and young adults, but is rare after age 24.

Efforts to prevent initiation of smoking should focus not only on adolescents but also on older youth and young adults.