Tobacco exposure and health : from fetal life to adulthood

Tobacco causes adverse effects on health from both active and passive exposure and in all stages of life. While health effects of tobacco have been extensively studied, the current state of knowledge in certain research areas is poor. As trends of tobacco products change, new questions arise. Additionally, some well researched topics still contain important knowledge gaps.

In Study I, the aim was to assess the validity of self-reported use of cigarettes, snus and e-cigarettes among Swedish young adults. Questionnaire data on tobacco use was compared to levels of cotinine, a biomarker of nicotine use, in urine samples. Overall, we found high validity of self-reported tobacco use compared to cotinine levels in the study population, with low levels of underreported tobacco use. The agreement between self-reported tobacco use and cotinine was particularly high among daily users, while somewhat lower for occasional users.

In Study II, the aim was to investigate cross-sectional associations between current snus use at 24 years and cardiometabolic health markers at 24 and 26 years in a Swedish birth cohort. Exclusive daily snus use was associated with higher body mass index (BMI) and waist circumference (WC) among women at 24 years, as well as with higher BMI at 26 years, as compared to non-tobacco users. Among men, using 24 cans of snus/week was associated with higher BMI at 26 years. No significant associations were observed between snus use and body fat %, glycemic status or blood pressure.

In Study III, the aim was to assess the association between early-life secondhand smoke (SHS) exposure (from maternal smoking during pregnancy and/or parental smoking during infancy) and development of atopic dermatitis (AD). Parental smoking during infancy was associated with a higher risk of AD up to 24 years, and particularly a phenotype defined by persistent AD with childhood onset of symptoms. Additionally, the association was stronger for AD with concurrent Immunoglobin E sensitization. Maternal smoking during pregnancy was associated with an increased AD risk up to 24 years, although only among participants not exposed to parental smoking in infancy. Furthermore, we found no gene- environment interaction between early-life SHS exposure and loss-of-function mutations in the FLG gene.

In Study IV, the aim was to investigate the long-term effects of early-life SHS on asthma and lung function, and to disentangle the effect from those of tobacco use in adolescence and/or young adulthood. Early-life SHS was associated with asthma up to 24 years, and the risk was particularly high during pre-school age. Early-life SHS was not associated with prevalent asthma at 24 years, while smoking in adolescence and/or young adulthood was associated with prevalent symptoms of wheeze. Early-life SHS exposure was associated with lower ratio between forced expiratory volume in 1 sec (FEV1) and forced vital capacity (FVC), irrespective of adolescent and/or young adulthood smoking. Smoking at a young age was additionally associated with a lower FEV1/FVC, regardless of early-life SHS exposure. Furthermore, dual exposure to early-life SHS and snus use in adolescent and/or young adulthood was associated with a lower FEV1/FVC.

The results of this thesis indicate that I) validity of self-reported tobacco use is high among Swedish young adults, II) snus use is associated with higher BMI and WC in young adults, particularly among women, but not with body fat %, glycemic status or blood pressure, III) early-life SHS exposure is associated with AD up to adulthood, and the association differs by disease phenotype but not by FLG mutations, and IV) early-life SHS exposure is associated with asthma and lower lung function up to adulthood, regardless of smoking in adolescence and/or young adulthood, and smoking at a young age is associated with prevalent wheeze and lower lung function regardless of early-life SHS exposure.

List of scientific papers

I. Zettergren A, Sompa S, Palmberg L, Ljungman P, Pershagen G, Andersson N, Lindh CH, Georgelis A, Kull I, Melén E, Ekström S, Bergström A. Assessing tobacco use in Swedish young adults from self-report and urinary cotinine: a validation study using the BAMSE birth cohort. BMJ Open. 2023 Jul 12;13(7):e072582 https://doi.org/10.1136/bmjopen-2023-072582

II. Zettergren A, Andersson N, Pershagen G, Lindh CH, Georgelis A, Kull I, Melen E, Ekstrom S, Ljungman P, Bergström A. Snus and cardiometabolic health markers among Swedish young adults. Nicotine & Tobacco Research. 2024 Nov 15:ntae267. https://doi.org/10.1093/ntr/ntae267

III. Zettergren A, Andersson N, Merritt, AS, Kull I, Ljungman P, Melén E, Pershagen G, Lundin S, Johansson EK, Ballardini N, Ekström S, Bergstrom A. Early-life secondhand smoke exposure and development of atopic dermatitis up to adulthood. [Manuscript]

IV. Zettergren A, Yu Z, Andersson N, Lindh CH, Merritt AS, Kull I, Pershagen G, Ljungman P, Melén E, Ekström S, Bergström A. Tobacco exposure from fetal life to adulthood and development of asthma and lung function. [Manuscript]