Long-term Impact of Prior Secondhand Tobacco Smoke Exposure on Respiratory Health

RationaleOngoing secondhand tobacco smoke (SHS) exposure is associated with worsened respiratory health, but little is known about the long-term impact decades after exposure ended. ObjectiveDetermine the long-term consequences of SHS exposure on respiratory health. MethodsPopulation-based, cohort study in subjects [≥]50 years old who had >1 year versus [≤]1 year of airline occupational SHS-exposure. Measurements and Main ResultsRespiratory health was the primary outcome measured by the St. Georges Respiratory Questionnaire (SGRQ). Key secondary outcomes included respiratory symptoms measured by COPD Assessment Test (CAT) and pre-bronchodilator lung function. The study enrolled 183 SHS-exposed and 59 unexposed subjects. SHS-exposed subjects were exposed to airline SHS for 16.1{+/-}9.3 years, which ended 27.5{+/-}9.4 years prior to enrollment. Prior SHS-exposure was associated with worse respiratory health based on a 6.7-unit increase in SGRQ (95% CI=[2.7, 10.7]; p=0.001) and 3-unit increase in CAT (95% CI=1.4, 4.6]; p<0.001) versus unexposed subjects, but was not associated with airflow obstruction defined by FEV1:FVC<0.7. Clinically-significant respiratory symptoms (CAT[≥]10) in SHS-exposed never smokers with preserved lung function (FEV1:FVC [≥]0.7 and FVC [≥]lower limit of normal) were associated with decreased respiratory and non-respiratory quality-of-life, reduced lung function that remained within the normal range, increased comorbidities and inhaled bronchodilator use, higher plasma CRP and SAA-1 and fewer sinonasal basal stem/progenitor cells versus asymptomatic (CAT<10) SHS-exposed subjects. ConclusionSHS is associated with a phenotype of impaired respiratory health almost 3 decades after exposure ended, consistent with a symptomatic form of COPD with preserved lung function recently described in smokers.