Prevalence of periodontal disease among Indigenous and non-Indigenous populations: protocol for systematic review and meta-analysis

BACKGROUND

Indigenous populations globally experience worse oral health than their non-Indigenous counterpart. Globally, the occurrence of periodontal diseases such as gingivitis and chronic periodontitis is high among Indigenous people. This systematic review aims to quantify, at a global level, the prevalence of periodontal disease among Indigenous populations compared to non-Indigenous populations.

METHODS

This review will only consider studies that have reported the prevalence (%) of periodontal disease among Indigenous and compared against non-Indigenous populations. Studies that have no comparative population or data only on one particular population or lack of data on periodontal clinical assessment will be excluded. An electronic search will be conducted using keywords and appropriate MeSH terms across several databases capturing both published and unpublished articles. The search will be conducted from the time of database inception to February 2021. After the initial search, duplicates will be removed, and the remaining titles and abstracts will be assessed for eligibility. The full text of eligible studies will be assessed by two independent reviewers who will also complete the critical appraisals and data extraction. Outcomes measures would be the mean prevalence (%) and standard deviation of periodontal disease among Indigenous and non-Indigenous populations. From the selected studies, we will conduct a random-effects meta-analysis using standardized mean difference as the effect measure. Forest plots will be used for the visualization of differences in the prevalence of periodontitis. A subgroup analysis will be conducted based on the definition of periodontitis, age, publication type, and geographical location. Heterogeneity among studies will be assessed by I² and chi-square test. Egger's test and funnel plots will be used to assess publication bias.

DISCUSSION

Our systematic review and meta-analysis will facilitate an increased understanding of the magnitude of periodontal disease inequalities that exist globally for Indigenous populations through pooled prevalence estimates. The findings will be helpful to design selective targeted preventive and interventional strategies for periodontal disease for reducing oral health inequalities at a global level.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020188531.

Genetic legacy of cultures indigenous to the Northeast Asian coast in mitochondrial genomes of nearly extinct maritime tribes

Background

We have described the diversity of complete mtDNA sequences from ‘relic’ groups of the Russian Far East, primarily the Nivkhi (who speak a language isolate with no clear relatedness to any others) and Oroki of Sakhalin, as well as the sedentary Koryak from Kamchatka and the Udegey of Primorye. Previous studies have shown that most of their traditional territory was dramatically reshaped by the expansion of Tungusic-speaking groups.

Results

Overall, 285 complete mitochondrial sequences were selected for phylogenetic analyses of published, revised and new mitogenomes. To highlight the likely role of Neolithic expansions in shaping the phylogeographical landscape of the Russian Far East, we focus on the major East Eurasian maternal lineages (Y1a, G1b, D4m2, D4e5, M7a2, and N9b) that are restricted to the coastal area. To obtain more insight into autochthonous populations, we removed from the phylogeographic analysis the G2a, G3a2, M8a1, M9a1, and C4b1 lineages, also found within our samples, likely resulting from admixture between the expanding proto-Tungus and the indigenous Paleoasiatic groups with whom they assimilated. Phylogenetic analysis reveals that unlike the relatively diverse lineage spectrum observed in the Amur estuary and northwestern Sakhalin, the present-day subpopulation on the northeastern coast of the island is relatively homogenous: a sole Y1a sublineage, conspicuous for its nodal mutation at m.16189 T > C!, includes different haplotypes. Sharing of the Y1a-m.16189 T > C! sublineages and haplotypes among the Nivkhi, Ulchi and sedentary Koryak is also evident. Aside from Y1a, the entire tree approach expands our understanding of the evolutionary history of haplogroups G1, D4m, N9b, and M7a2. Specifically, we identified the novel haplogroup N9b1 in Primorye, which implies a link between a component of the Udegey ancestry and the Hokkaido Jomon.

Conclusions

Through a comprehensive dataset of mitochondrial genomes retained in autochthonous populations along the coast between Primorye and the Bering Strait, we considerably extended the sequence diversity of these populations to provide new features based on the number and timing of founding lineages. We emphasize the value of integrating genealogical information with genetic data for reconstructing the population history of indigenous groups dramatically impacted by twentieth century resettlement and social upheavals.