Introduction:
Tobacco control policies are proven to reduce smoking prevalence. It has been suggested that tobacco control measures are less effective where smoking prevalence has significantly declined, as the remaining smokers have “hardened”. Our aim was to empirically evaluate the “hardening hypothesis” at the population-level in the European Union and analyse the determinants of hardcore smoking.

Methods:
We conducted two separate analyses in the 28 EU Member States using data on smoking from the Eurobarometer surveys (2009-2017, n=110,241); a multilevel logistic regression analysis with two levels (individual and country) with hardcore (daily smokers, smoking ≥15 cigarettes per day [cpd] that have not attempted to quit in the last 12 months) and light (<5 cpd) smoking as dependent variable and time as the main independent variable, controlling for individual (sex, age, education, difficulties to pay the bills, marital status, type of community) and ecological (GDP and Tobacco Control Scale score) variables. At an ecological-level, we conducted a panel-data fixed-effects linear regression to investigate changes over time in the percentage of hardcore smokers in relation to standardized smoking prevalence at the country level.

Results:
We studied 29,010 current smokers (43.8% hardcore and 14.7% light smokers). The odds of being a hardcore smoker were increased over time in middle-age men and people with difficulties to pay the bills. The odds of being a light smoker significantly declined among women over time (OR=0.98, 0.96-0.99 per calendar year). At an ecological-level, the prevalence of hardcore smoking among adults increased by 0.55 (0.14-0.96) percentage points per each additional percentage point in the overall increase in smoking prevalence.

Conclusion:
Our study does not support the “hardening hypothesis” in the EU between 2009 and 2017 but rather suggests a softening of the smoking population. Existing tobacco control policies are likely to be suitable to further decrease smoking prevalence in Europe.