The role of secondhand smoke in allergic rhinitis: a systematic review

The objective of this work was to systematically review existing literature on the association between allergic rhinitis (AR) and secondhand smoking (SHS) in children and adults.

We performed a literature search encompassing the last 25 years in PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane CENTRAL, Web of Science, Scopus, and EMBASE. Inclusion criteria included English language papers containing original human data with greater than 6 subjects. Data was systematically collected on study design, patient demographics, clinical characteristics/outcomes, and level-of-evidence (Oxford Center of Evidence-Based Medicine). Quality assessment of the studies was performed using the Newcastle-Ottawa scale. Two investigators independently reviewed all manuscripts.

The initial search yielded 590 abstracts, of which 40 articles were included. 12 (37.5%) of the 32 articles studying children and 5 (62.5%) of the 8 articles studying adults showed a statistically significant association between AR and SHS. One article was a prospective cohort study (Level 2b) and all other articles were case-control studies (Level 3b). For characterizing AR, 10 (25%) studies included skin-prick testing and 5 (12.5%) used in vitro testing. For determining presence of SHS, 39 (97.5%) of the studies used questionnaires and 1 article used a cotinine/creatinine ratio.

This review demonstrated a majority of adult studies vs a minority of children studies found a significant association between AR and SHS. However, the percent difference between age groups was not statistically significant. Further higher-quality studies with validated methods for diagnosing AR and quantifying SHS exposure should be performed to better evaluate the relationship between AR and SHS in adults and children.