Teenagers may be less likely to start smoking if they engage in moderate-to-vigorous physical activity (MVPA) from childhood, a study has found.

The research, conducted by the Universities of Bristol and Exeter in partnership with the University of Eastern Finland, was published in the Journal of Behaviour Research and Therapy.

Childhood and teenage tobacco smoking is a preventable risk factor for premature structural and functional cardiac damage already in the mid-twenties. Physical activity intervention studies have reported reduced smoking rates among adults. However, physical activity studies in preventing smoking in children and adolescents have been inconclusive due to short study durations, small population sizes, and lack of accelerometer-measured physical activity data.

The study is the largest follow-up of accelerometer-based MVPA and smoking behaviour in the young population in the world.

The researchers drew 2,503 children from the University of Bristol’s ‘Children of the 90s’ cohort who were followed from 11 years old until 24 years. The prevalence of smoking at ages 13, 15, and 24 years was 1.5 per cent, 13.5 per cent, and 26.6 per cent, respectively.

Establishing a starting point

At baseline, the children spent six hours per day sedentary, six hours per day engaging in light physical activity, and approximately 55 minutes per day in MVPA.

At follow-up in young adulthood, nine hours per day were spent sedentary, three hours per day in light physical activity, and approximately 50 minutes per day in MVPA.

The children’s fasting blood samples were also repeatedly measured for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, glucose, insulin, and high-sensitivity C-reactive protein. Blood pressure, heart rate, socio-economic status, family history of cardiovascular disease, as well as dual-energy X-ray absorptiometry measured fat mass and lean mass were accounted for in the analyses.

According to the study, six of 1000 children who engaged in MVPA at age 11 had initiated tobacco smoking by age 13, while the prevalence of smoking in the whole age group was 15 out of 1000. In other words, the risk of initiating tobacco smoking may be prevented in 60 per cent of 13-year-olds who would have taken their first tobacco puff, because of childhood participation in MVPA.

Young adult activity levels

In the follow-up, a more modest preventive effect was observed. Continuous exposure to MVPA from childhood through young adulthood could prevent smoking in eight out of 1000 young adults, when the prevalence of smoking was 266 out of 1000 young adults.

In addition, teenagers who were non-smokers at ages 13 and 15 years spent 15 more minutes per day in MVPA by age 24 years when compared with those who had a history of smoking at 13 and 15 years.

Childhood sedentariness was not prospectively associated with the risk of initiating and persistently smoking tobacco.

Andrew Agbaje, a physician and associate professor of Clinical Epidemiology and Child Health at the University of Eastern Finland, said, “The MVPA-smoking preventive potential had a strong causal consistency across all tested statistical models, but the effect diminished by young adulthood. It’s all the more important that legislation protects young people against tobacco smoking and nicotine use initiation.

“Stopping smoking in adulthood is good but late since a residual long-term risk of heart disease for the next 30 years still exists. Thus, preventing childhood smoking initiation is critical to lifelong health and these findings may be extrapolated to vaping and electronic cigarette use in teenagers since the same active ingredient in both smoke and smokeless tobacco is nicotine.

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