The role of demographic and behavioural change for the long-term decline in daily smoking in Norway.

Background: The aim of this paper was to compare the effects of demography (population aging and the increasing fraction of tertiary educated) and behaviour (intra-cohort ageing and inter-cohort change) on long-term change in the fraction of daily smokers (FrS), using a counterfactual framework.

Methods: Using aggregated data on smoking prevalence, education and population size from Norway 1978 to 2017, the probabilities of smoking for men and women were calculated using a pseudo-panel approach. From these estimates, four counterfactual scenarios of FrS were constructed by holding the age effect, the cohort effect and the distribution of age and education constant over time.

Results: FrS decreased from 45 to 14% among men, and from 33 to 14% among women over the study period. Holding the age distribution constant did not have any substantial effect on FrS. Holding the distribution of education constant led to a five percentage points increase in FrS among women, but not among men. In the case of no intra-cohort ageing, FrS would have been 11/12 percentage points higher among women/men. The corresponding figures for no inter-cohort change were 13 points for women and 27 points for men.

Conclusions: If the age distribution had remained stable over time, FrS would have been almost identical to the current level. In contrast, if smoking behaviour had remained stable over the life course or between birth cohorts, FrS would have been substantially higher than it is today. These results highlight the large cumulative effect of reducing smoking uptake in successive cohorts.