Higher asthma risk in offspring of parents starting snus use before conception: findings from the RHINESSA study

<bold>Background:</bold> Research suggests preconception exposure to smoking may impact offspring lung health, and that epigenetic mechanisms may be at play. Thus, parental snus initiation before offspring conception may potentially influence asthma risk in offspring. <bold>Aims:</bold> To investigate the association of parental snus use before conception with offspring asthma. <bold>Methods:</bold> Data from the population-based Respiratory Health in Northern Europe, Spain and Australia (RHINESSA) study (2013-16) across Norway, Sweden, Denmark, Iceland and Estonia were analyzed. Parental reports (from one parent) on their age of snus initiation were categorized as <italic>never</italic> (reference), <italic>preconception</italic> (≥2 years before offspring birth), and <italic>postconception</italic> (after offspring birth). Offspring asthma (never/ever) was reported by the parent. Logistic regressions clustered by study center and adjusted for parental age, sex, and offspring sex were conducted. Sensitivity analyses included never-smoking parents and sex-specific parent-offspring pairs. <bold>Results:</bold> This two-generation analysis included 2005 parent-offspring pairs (mean age: parent, 36 years; offspring, 9 years). Offspring of parents who reported preconception snus use (198 pairs) had higher asthma risk (OR 1.94; 95%CI 1.23-3.10) compared to offspring of never-snus users (1706 pairs). This association remained for offspring of never-smoking parents (90 pairs; 2.29; 1.12-4.30). Sex-specific analyses revealed associations in father-daughter only (2.86; 1.29-6.36). Weaker associations were found with postconception snus use. <bold>Conclusions:</bold> Parental snus use before conception may possibly increase asthma risk in offspring, even among children of never-smoking parents.