Tooth loss is associated with reduced muscle mass: the mediating roles of DII and CDAI

Background Tooth loss may contribute to sarcopenia not only through impaired mastication but also by altering diet-related inflammation and antioxidant capacity. We investigated whether the dietary inflammatory potential index (DII) and composite dietary antioxidant capacity (CDAI) mediate the association between tooth loss and skeletal muscle mass. Methods Using NHANES 2011–2018, we included adults aged ≥ 20 years who had dentition examinations and DXA-derived appendicular skeletal muscle measurements (n = 10,080). Dentition status was categorized by the number of remaining natural teeth (NRT; <20 vs ≥ 20) and functional tooth loss (NFTL; >16 vs ≤ 16). ASMI was calculated as ASM/height². We conducted weighted multivariable regression, performed prespecified subgroup analyses, and applied parallel mediation with 5,000 bootstrap resamples. Results In fully adjusted models, more favourable dentition status was independently associated with higher ASMI (NRT ≥ 20: β = 0.15, 95% CI 0.04–0.26, P = 0.01; NFTL ≤ 16: β = 0.20, 95% CI 0.07–0.33, P = 0.004). Both DII and CDAI partially mediated these relationships (NRT: 10.09% and 4.61%; NFTL: 7.98% and 3.72%; all P < 0.05). The associations were generally consistent across strata and were more pronounced among men, current smokers, and individuals with dysglycaemia-related phenotypes. Conclusions Among U.S. adults, tooth loss was associated with lower skeletal muscle mass, and diet-related inflammatory potential and oxidant capacity explained a measurable proportion of this association. The results support an “oral health–dietary inflammation/oxidation status–muscle” axis and suggest that improving diet quality may represent a modifiable pathway for sarcopenia prevention, particularly for adults with poor dentition status.