Evolution and characteristics of studies estimating attributable mortality to second-hand smoke: a systematic review

Background Several studies have estimated the impact of second-hand smoke (SHS) exposure on mortality in the population of different countries. This study aimed to identify and describe studies that have estimated the attributable mortality (AM) associated with SHS exposure in the adult population. Methods A literature search was conducted in MEDLINE, EMBASE, Cochrane Library and CINAHL databases up to January 2023. Studies that estimated the AM associated with SHS exposure in the adult population and used a prevalence-dependent method were included. The main characteristics of the studies and their results were described. Results Fifty-three studies were included. Most of them were conducted in North America (n = 13), Europe (n = 14) and China (n = 6) and included lung cancer (n = 46) or ischaemic heart disease (n = 22) as causes of death. There was considerable variety in the population under study regarding the relationship with tobacco: non-smokers (n = 30); never-smokers (n = 9); both non and never-smokers (n = 2); the whole population (n = 1) and not known (n = 11). The age at which AM was estimated also varied between studies, ranging from 15 to 40 years and older. Conclusions Studies estimating AM associated with SHS exposure are heterogeneous in terms of the causes of death studied, the age at which mortality is attributed, or the population to which mortality referred: consensus should be reached. Despite their importance, studies assessing AM to SHS are infrequent in low- and middle-income countries