Household adult smoking behaviors and prevalence of asthma in Greek schoolchildren: five surveys during 1998-2018.

Environmental tobacco smoke exposure is a well-recognized risk factor for asthma development and poor asthma control in children. However, the relationship between changes in parental smoking habits over time and the prevalence of childhood asthma remains largely unknown. Our objective was to investigate the trends of parental smoking behaviors in relation to childhood wheeze/asthma rates over a 20-year period. A standardized questionnaire on household overall smoking and household indoor tobacco smoking (HITS) habits was distributed to 8-9-years-old school children in the context of five cross-sectional surveys conducted in 1998 (n=3,076), 2003 (n=2,725), 2008 (n=2,688), 2013 (n=2,554) and 2018 (n=2,648). The parental overall smoking and HITS rates have substantially decreased during the study period (p-for-trend<0.001). However, while HITS declined among the fathers of asthmatic and non-asthmatic children as well as among the mothers of non-asthmatic ones (p-for-trend<0.001), it remained unchanged in the case of the mothers of asthmatic participants (p-for-trend 0.283). The mothers of asthmatic children consistently reported more HITS than those of non-asthmatic participants, while prevalence changes of current wheeze/asthma over the surveillance period were in complete agreement with changes in maternal HITS (cross-correlation coefficient 0.918 at zero-year lag) but not with paternal smoking behaviors. Overall and indoor smoking rates of school children's adult family members declined substantially during the 1998-2018 period in Greece. However, no such trend was noted among mothers of asthmatic children, while temporal changes in maternal indoor smoking rates occurred in parallel with those of childhood asthma prevalence.