Associations of smoke-free policies in multi-unit housing with smoking behavior and second-hand smoke exposure: A systematic review

Background and aim
Although considerable progress has been made regarding the implementation of smoke-free policies (SFPs), many people continue to be exposed to second-hand smoke (SHS) in the home environment. The aim of this study was to conduct a systematic review on the association of SFPs in multi-unit housing (MUH) with smoking behavior and SHS exposure.

Methods
In August 2022, we searched five online databases: PubMed, Embase, Web of Science, PsycINFO and CENTRAL. Keywords included terms for SFPs, MUH, smoking behavior and exposure to SHS. We searched for studies that focused on regular combustible cigarettes. Due to the high heterogeneity in methodology and outcomes of the included studies, a meta-analysis was not performed.

Results
Our search yielded 4750 articles. All of them were screened (24 based on full-text), and 17 met the inclusion criteria. All studies were published between 2001 and 2022. Most studies were conducted in the United States (n = 16) and used a cross-sectional design (n = 7) or a longitudinal design (n = 7). Seven studies evaluated smoking behavior. Five of them reported that SFPs in MUH were statistically significantly associated with decreases in either current smoking, smoking quantity, smoking frequency or smoking cessation. Fourteen studies evaluated exposure to SHS. Ten reported that SFPs in MUH were statistically significantly associated with decreases in self-reported exposure to SHS, airborne nicotine levels and particulate matter levels.

Conclusions
Smoke-free policies in multi-unit housing appear to be associated with reduced smoking behavior and second-hand smoke exposure. Successful implementation depends on accessible cessation support and effective enforcement.