Introduction:
Aim: To synthesize the available evidence in scientific papers of smokefree legislations (SFL) effects on respiratory diseases (such as asthma, chronic obstructive pulmonary disease [COPD]) and lung infections (pneumoniae, bronchitis) among all populations (adults, children or general population).

Methods:
Systematic review and meta-analysis were carried out. PRISMA guidelines were followed. A search between January 1995 and February 2015 was performed in PubMed, EMBASE, Cochrane Library, Scopus, Web of Science, and Google Scholar databases. The inclusion criteria were: 1)Original scientific studies concerning SFL, 2) With data before and after its implementation and 3) assessment of the impact of SFL on respiratory diseases. A meta-analysis was performed using the Review Manager (RevMan, version 5.3). The effect of SFL was estimated by risk ratios (RR) and risk difference (RD). Pooled effect measures were computed applying the inverse-variance method in a random-effect model. Heterogeneity was quantified with the I2 statistic. Subgroup and sensitivity analysis were performed.

Results:
17 studies reported effects on asthma, 9 on COPD and 4 on lung infections admissions. All the meta-analysis concerned comprehensive SFL settings. Six studies were included in a meta-analysis for asthma admissions in general population, 5 in children and 7 in adults. There was a significant decrease of 13% after SFL in general population (RR 0.87; 95%CI 0.81, 0.93; I2 78%) and of 15% both in children (95%CI 0.79, 0.91; I2 87%) and adults (95%CI 0.73, 0.99; I2 65%). In contrast, the 6 studies for COPD admissions showed a non significant decrease of 20% after SFL (95%CI 0.63, 1.00; I2 96%). For lung infections admissions, only 2 studies showed a non significant decrease of 14% after SFL (95%CI 0.67, 1.10; I2 55%).

Conclusions:
SFL appears to decrease rates of admissions for asthma in all populations in comprehensive settings but not for COPD or lung infections.

Funding:
This work was supported by the Instituto de Salud Carlos III (Institute of Health Carlos III, ISCiii) of the Ministry of Economy and Competitiveness (Spain) through the Network for Prevention and Health Promotion in Primary Care (redIAPP, RD12/0005/0001; RD16/0007/0001), co-financed with European Union ERDF funds.