Oral Candida carriage in smokers and tobacco users: A systematic review and meta-analysis of observational studies

To synthesize evidence from observational studies that evaluated the association between smoking and smokeless tobacco with oral Candida carriage.

Following the PRISMA guidelines, we searched through PubMed/MEDLINE, Web of Science, Embase, and Scopus without restrictions until April 2020 for studies that assessed this association. Following study retrieval and selection, relevant data were extracted, and the risk of bias was assessed by two independent authors using the Newcastle-Ottawa Scale. A fixed-effect meta-analysis was performed due to insignificant heterogeneity between studies.

We identified 14 studies that were eligible for inclusion in this review. The pooled odds ratio (OR; six studies) for Candida carriage among smokers and non-smokers was 2.15 (95% confidence interval [CI]: 1.47, 3.14; I² = 8%; P < 0.0001). The OR (five studies) for Candida carriage among smokeless tobacco users and non-users was 1.77 (95% CI: 1.29, 2.44; I² = 46%; P = 0.0004).

Our findings suggest a significant relationship between smoking/smokeless tobacco users and oral Candida carriage. However, observational studies cannot clarify whether the observed epidemiologic association is a causal effect or the result of some unmeasured confounding variables. Therefore, continued efforts to measure the association between smoking and oral Candida carriage are required.