Household secondhand smoking and asthma exacerbation during the covid-19 pandemic in Japanese junior high school students

ABSTRACT

Background: There is evidence that secondhand smoke exposure, particularly indoor smoking exposure, increases the risk of asthma exacerbations. This relationship might be modified in the era of a pandemic of covid-19 when the overall spread of viral infection may decrease due to precaution. Method(s) In this public school-based longitudinal paper questionnaire study in 2019 and 2021, the students and parents of junior high schools were asked whether the student had ever been diagnosed as wheezy bronchitis or asthma by a doctor and whether they had wheezing or whistling in the chest in the last 12 months. The presence of smokers in the household and their location of smoking (outside only or indoor) were also asked. Student sex, parental age, household income, and the region of the school were employed as covariates. Result(s) Of 1926 students who registered in 2019, 1482 (76.9%) responded in 2021. A total of 351 (23.4%) ever had a doctor diagnosis of asthma. The rate of students who reported asthma symptoms decreased from 27.4% in 2019 to 8.6% in 2021. The rate of asthma symptoms significantly increased depending on the presence of smokers in the household and the location of smoking in 2019;22.1% (44/199) in the students with no smokers in the household, 29.2% (19/65) smokers with smokers who smoke only outside the home, and 39.1% (34/87) with indoor smokers. This association remained significant in 2021, although there were some improvements in the overall smoking status in the household;5.5% (12/217), 12.3% (7/50), and 14.3% (11/77), respectively. The adjusted odds ratio of asthma symptoms in the students with indoor smokers, as compared with no smokers in the household, was 1.92 (95% confidential intervals (CI), 1.06-3.48) in 2019 and 2.92 (95% CI, 1.03-8.21) in 2021. Conclusion(s) These results suggest that household indoor smoking exposure may have an adverse effect on asthma symptoms even in the era of the covid-19 pandemic.