Age-associated changes in nicotine dependence

Objectives: Nicotine is the primary factor responsible for tobacco dependence among individuals who smoke. Nicotinic receptors and nicotine-associated metabolism, two significant aspects of nicotine dependence, are influenced by age. To date, however, the relationship between age and nicotine dependence has not been investigated.

Study design: Cross-sectional.

Methods: Data were obtained from the national smoking cessation programme for South Korea. Data obtained from current smokers in 2008 (n = 338,566) were used as baseline measures. Nicotine dependence was determined by the Fagerström Test for Nicotine Dependence (FTND). Cigarettes per day (CPD) and FTND were the dependent variables. As CPD is a major component of FTND, scores on the FTND minus scores related to CPD were also used as a dependent variable. The relationships between age and the dependent variables (FTND, CPD, partial FTND) were investigated. Quadratic regression models were used to test the non-linear relationship between age and nicotine dependence after adjusting for other covariates.

Results: Analyses relying on nicotine dependence (FTND and partial FTND scores) and CPD produced similar results in relation to age. Specifically, the values of all three dependent variables increased with age until approximately 50 years of age, at which point they decreased. Additionally, nicotine dependence and CPD were associated with age of smoking initiation, smoking duration, alcohol-related problems, body mass index and residential area. After adjusting for other nicotine-dependence-related factors, the linear and quadratic terms of age were statistically significant in the multiple regression models.

Conclusions: In the present study, both nicotine dependence and CPD displayed an inverse U-shaped relationship with age, with a significant peak at 50 years of age. The results suggest that tobacco control policies should target issues related to nicotine dependence according to age group.