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Secondhand smoke in childhood: The world‐wide burden of a major public health‐care problem

Recent evidence attests that the health-care burden of secondhand smoke is particularly high in the childhood. Since little information is currently available on the epidemiologic relationship between secondhand smoke on health loss or mortality in childhood to the best of our knowledge, we planned this study to specifically address this question. An electronic search was carried out in Global Health Data Exchange registry, a large database of health-related data maintained by the Institute for Health Metrics and Evaluation, using the keywords ‘secondhand smoke’ and ‘all causes’ in the categories ‘DALYs’ (disability-adjusted life years) or ‘deaths’. The database search was then combined with the epidemiologic variables ‘year’ (from 1990 to 2017), ‘age’ (from <1 to 9 years old) and ‘location’ (SDI Regions, where SDI stands for socio-demographic index). The 2017 is the last searchable year in the Global Health Data Exchange registry, and was hence selected for reporting updated information on the adverse health impact of secondhand smoke in childhood world-wide. The output of the electronic search was downloaded in comma-separated values, imported into an Excel file (Microsoft, Redmond, WA, USA) and analysed with Analyse-it (Analyse-it Software Ltd., Leeds, UK). Simple (Pearson’s correlation) regression analyses were used for assessing potential associations (and their relative 95% confidence interval (95% CI)) among epidemiologic measures. The study was performed in accordance with the Declaration of Helsinki and under the terms of relevant local legislation. Ethics board approval is unnecessary at the local institution (University Hospital of Verona) for articles based on free scientific databases searches. The values of world-wide childhood DALYs and deaths due to secondhand smoke exposure are currently estimated at 5.65 million (1.0% of all DALYs) and 63 823 (1.1% of all deaths), respectively, the vast majority of which (~75%) is in children aged <1 years. The last 28-year world-wide trend (i.e. between 1990 and 2017) is shown in Figure 1, which reveals that both health loss and mortality due to secondhand smoke have dramatically declined, by approximately 80%, during the last 28 years. The reduction of health loss and deaths has been very similar across age ranges, being comprised between 68 and 81% for DALYs and between 72 and 82% for mortality, respectively. Importantly, an inverse linear relationship can be observed between SDI and both childhood DALYs (r = −0.95; 95% CI −1.00 to −0.44; P = 0.012) or deaths (−0.95; 95% CI −1.00 to −0.43; P = 0.013) due to secondhand smoke. Although continuous exposure to secondhand smoke remains a serious public health-care issue in children, since it may cause or predispose to a vast array of health problems such as premature death, sudden infant death syndrome, respiratory infections and asthma, the results of our investigation are in keeping with those published in other reports, suggesting that passive smoking seems to have significantly declined in the past 40 years worldwide. This is most likely the result of effective policies of tobacco control and legislations prohibiting cigarette smoke in public spaces, which have been established and recently reinforced in many countries world-wide. The second important finding that has emerged from our analysis is that the burden of secondhand smoke on children heath is dramatically magnified in countries with low socio-economic status, which shall hence be targeted with more aggressive policies aimed at limiting secondhand smoke exposure in highly vulnerable subjects such as neonates and children.