Starting smoking at age 15 years or younger may increase the likelihood of experiencing respiratory symptoms by up to 80% by age 28 years, according to a recent study.

In a prospective study presented at the European Respiratory Society Congress in September 2024, investigators at Umeå University, Sweden, indicated that patients who began smoking before the age of 18 had a higher risk of developing respiratory symptoms by early adulthood. The study followed a cohort of children from age 8 to 28, examining the relationship between smoking onset, pack-years, and respiratory health outcomes.

The cohort included 3,430 patients, with 22% reporting daily smoking at some point. Among these patients, 29% of them started smoking at age 15 years or younger, 35% began smoking between 16 and 17 years, and 35% started at age 18 years or older. At age 28, 53% of the patients reported at least one respiratory symptom, with wheezing (36%) and sputum production (30%) being the most common. Additionally, 23% of the patients reported a diagnosis of asthma. The unadjusted analysis showed an association between starting smoking at age 15 or younger and pack-years with asthma, but this link was no longer significant after adjusting for other variables.

After adjusting for sex, family history of asthma, childhood exposure to smoking, and educational level, the analysis revealed that earlier smoking initiation was associated with a higher risk of respiratory symptoms. Smokers who started at age 15 or younger had an 80% increased risk of respiratory symptoms compared with nonsmokers (odds ratio [OR] = 1.8, 95% confidence interval [CI] = 1.2–2.7). Each additional pack-year of smoking increased the likelihood of symptoms by 10% (OR = 1.1, 95% CI = 1.0–1.2). 

The study had no conflicts of interest disclosed.