Global prevalence of oral pigmentation and its related factors: a systematic review and meta-analysis

Oral pigmentation is due to the accumulation of one or more pigments in tissues, causing changes in the color of the oral mucosal surfaces. Understanding the exact global prevalence of oral pigmentation and its associated factors helps researchers make the proper interventions at the right time; in this respect, the objective of the present systematic review and meta-analysis was to determine the global prevalence of oral pigmentation and its related factors.

A systematic review and meta- analysis were conducted using the following databases: Magiran, SID, Scopus, Embase, PubMed, Web of Science (WoS), and Google Scholar. The search was run to retrieve articles published from inception until July 2021, and the following keywords were applied in the search strategy: "Epidemiolo*", "Prevalen*", "Factor*", "Pigment*", "Mouth", and "Oral". The I² index was used to assess the heterogeneity of the studies, and Egger's test was used to examine the publication bias.

Sixty-nine articles, with a sample size of 70,668 people, meeting the inclusion criteria were included in the study. The pooled of prevalence of oral pigmentation was estimated to be 20.8% (95% confidence interval: 17.1-1.25%). The prevalence of oral pigmentation raised significantly towards the end of the timespan covered by the study (P˂ 0.001). The majority of the examined studies reported that the prevalence of oral pigmentation is significantly higher in men, smokers or those exposed to secondhand smoke, people with fair skin, and who were affected by Yusho patients.

The results of the present study show that the prevalence of oral pigmentation is high, with higher prevalence in men, smokers or those exposed to cigarette smoke, people with fair skin, and Yusho patients compared to other groups. It is recommended that. these findings be used in policy makers' decisions to deliver better health care.