A Theoretical Investigation of the Oral-Systemic Disease Nexus in Sub-Saharan African Populations

The bidirectional relationship between oral disease and systemic conditions including cardiovascular disease, diabetes, and preterm birth has been established in Western populations, yet the specific mechanisms, effect magnitudes, and clinical implications of this nexus in sub-Saharan African populations require original theoretical investigation that accounts for the region's distinct disease burden and health system contexts. This study conducted an original theoretical investigation of the oral-systemic disease nexus in sub-Saharan African populations, with empirical grounding in Nigeria. A constructive theory-building methodology was employed, drawing on systematic review of oral-systemic relationship literature for SSA (78 publications from 2018 to 2024), empirical analysis of national survey datasets exploring oral disease and systemic disease co-occurrence in three zones, and expert consultation with 25 oral medicine, medicine, and obstetrics specialists. Systematic review confirmed that existing evidence on the oral-systemic nexus in SSA is predominantly from South Africa, with Nigeria providing minimal data, and that existing theoretical models inadequately account for the high infectious disease co-morbidity burden affecting inflammatory pathway modelling in African populations. The original Sub-Saharan African Oral-Systemic Nexus Theory proposes three SSA-specific pathway modifications: malaria-periodontal immune cross-activation, protein-energy malnutrition amplification of oral infection systemic effects, and HIV-mediated oral-systemic inflammatory bidirectionality. Expert review by 22 specialists confirmed the framework's theoretical originality. Recommendations include multi-site prospective cohort studies examining these pathways in Nigerian hospitalised populations.

Keywords: oral-systemic disease nexus, sub-Saharan Africa, periodontal disease, theoretical framework, Nigeria