Passive smoking is a risk factor for poor sleep quality of non-smokers. Studies have found that poor cooking conditions, improper cooking behaviors, and poor ventilation conditions in kitchen are also related with sleep quality. However, few reports have demonstrated the individual effects of above factors and their interaction effects with passive smoking on nonsmokers' sleep quality.

This study investigates the individual effects of cooking conditions, cooking behaviors, and ventilation in kitchen as well as their interaction effects with passive smoking on sleep quality of non-smokers.

Questionnaire surveys and physical examinations were conducted among 514 non-smoking employees in a Guangxi enterprise in September 2017 using cluster sampling. Sociodemographic information, passive smoking, cooking conditions (such as kitchen area), cooking behaviors (such as whether preheating oil to smoke before cooking), and ventilation conditions (such as the usage of ventilators and ventilation effect) in kitchen were collected through questionnaires. Sleep quality was evaluated by Pittsburgh Sleep Quality Index (PSQI). According to the study objective, participants who had been previously diagnosed or self-reported chronic diseases, anxiety, and depression, as well as those with major information missing were further excluded. Eventually, a total of 426 non-smokers were included in this study. Logistic regression was used to analyze the individual and interaction effects of passive smoking, cooking conditions, cooking behaviors, and ventilation conditions in kitchen on sleep quality of non-smokers.

The total PSQI score of the participants was 5.50±0.14. The total PSQI score in the group with passive smoking exposure was higher than that in the group without (P=0.002). Passive smoking (OR=2.06, 95%CI: 1.34-3.16) and poor kitchen ventilation (OR=2.00, 95%CI: 1.32-3.04) were the risk factors affecting the overall sleep quality of the non-smokers. The interaction analysis results showed that compared with the non-smokers without passive smoking and with good cooking conditions/cooking behaviors/ventilation conditions in kitchen, the nonsmokers with passive smoking plus kitchen area ≤ 5m² (OR_{sleep latency}=2.47, OR_{overall sleep quality}=2.35, P < 0.05), plus preheating oil to smoke before cooking (OR_{overall sleep quality}=2.59, P < 0.05), plus without mechanical ventilation in kitchen (OR_{daytime dysfunction}=1.97, OR_{overall sleep quality}=2.13, P < 0.05), or poor kitchen ventilation (OR_{sleep latency}=2.13, OR_{daytime dysfunction}=1.58, OR_{overall sleep quality}=3.86, P < 0.05) had higher risks of poor sleep quality.

Passive smoking and poor ventilation in kitchen are both risk factors for overall sleep quality of non-smokers, and the coexposure to passive smoking and kitchen area ≤ 5 m², preheating oil to smoke before cooking, without mechanical ventilation or poor ventilation in kitchen are more harmful.