Hardening or softening? An observational study of changes to the prevalence of hardening indicators in Victoria, Australia, 2001-2016.

BACKGROUND: The hardening hypothesis predicts that as smoking prevalence declines, remaining smokers will be more heavily addicted to nicotine and/or less interested in quitting. We tested this hypothesis in a population exposed to a comprehensive tobacco control programme over a 16-year period.
METHODS: Annual cross-sectional surveys randomly sampled adults (aged 26+) in the state of Victoria, Australia, between 2001 and 2016. Until 2010, participants were recruited through random digit dialling to landline telephones; from 2011, sampling frames also included mobile phones. Logistic regressions assessed changes over time in the prevalence of smoking and each hardening indicator; additional models examined interactions by sex, age, education and socioeconomic status.
RESULTS: Smoking prevalence declined significantly between 2001 and 2016 (20.1%-13.0%), as did the prevalence of seven hardening indicators: daily smoking, heavy consumption, no quit attempt in the past 5 years or past 12 months, no intention to quit in the next 6 months or next 30 days, and happiness to keep smoking. In addition, the proportion of smokers defined as 'hardcore' decreased from 17.2% to 9.1%. On the whole, hardening indicators decreased to a similar extent among demographic subgroups.
CONCLUSIONS: These results are inconsistent with the hardening hypothesis. Rather, they suggest that a comprehensive tobacco control programme that combines provision of cessation support to individual smokers with implementation of population-level interventions to drive all smokers towards quitting, can successfully reduce both smoking prevalence and levels of dependence and desire to keep smoking among the remaining population of smokers. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.