Effect of smoking initiation age on nicotine dependence

Abstract

Abstract Background Tobacco is widely recognized as a risk factor for major cardiovascular morbidity and mortality worldwide. Although the legal smoking age to purchase tobacco is 18 years old (yo) in most countries in the world but it ranges from 15 to 21 yo. If a person does not start using tobacco until the age of 21, they are more likely to remain tobacco-free for the rest of their lives. In 2019, the Tobacco 21 [T21] federal law came into effect in 2019 in the US, where the US government raised the minimum age for purchasing tobacco products from 18 to 21 yo and saw a subsequent decline in tobacco use. People who start smoking at a young age show greater nicotine dependence, and lower quit rates. However, the details of the effect of smoking initiation age on the smoking cessation (SC) rates and nicotine dependence are not known. Purpose The purpose of this study is to demonstrate the effect of age at smoking initiation on SC rate, and nicotine dependence using 20 yo as the cut-off point, which is the legal smoking age in Japan. We also examined the effect of age at smoking initiation on various smoking related parameters. Methods Among smokers who visited our SC clinics, the participants (smokers) who visited our SC clinics were divided into 2 groups (<20 yo and ≥20 yo) and 4 groups (≤17 yo, 18-19 yo, 20-21 yo, ≥22 yo) based on their age of smoking initiation. The prevalence and association between the various parameters including CV biomarkers were compared between 2 groups by using Fisher’s exact test, and unpaired t-test. Results The study participants consisted of 1382 smokers [29.8% female] with a mean age of 58.2±13.1 yo at the time of first visit to our clinic. Compared with the group of smoking initiation age of ≥20 yo, the group of smoking initiation age group <20 yo reported a higher number of cigarettes/day (25±12 vs 22±12, p value<0.001 and adjusted p-value=0.002), higher respiratory CO levels (19.3±13.5 vs16.5±11.9), and higher FTND score (7.4±2.0 vs 6.3±2.2) with significant p-values and adjusted p-value of <0.001. The successful SC rate was lower in the group ≥20 yo with 56% as compared to the group <20 yo with 45.5% (p-value=0.001). When comparing the 4 groups, a further increase in the age of smoking initiation to ≥22 yo leads to an additional decrease in nicotine dependence. Conclusions The present study shows that smoking initiation at the age of 20 yo or older is associated with lower nicotine dependence and depressive tendency, and a higher rate of successful SC compared with smoking initiation at age <20 yo. A further increase in the age of smoking initiation age to 22 yo or older leads to a further decrease in nicotine dependence. Our study may explain the rationale for reducing smoking through the T21 policy in the USA. The present study underlines the importance of raising the legal age of tobacco purchase to 22 yo worldwide.