The association between tooth loss and cognitive decline in the aged population: The mediating role of HDL-cholesterol

Objective: Tooth loss and its impact on cognitive impairment have become a heated topic over the past decade as the global population continues to age. Despite the proliferation of research in this area, the underlying mechanism linking tooth loss and cognitive decline remains poorly understood. Limited investigation has been conducted to explore the potential role of lipid metabolism and its impact on the association between tooth loss and cognitive function. This study endeavored to identify the role of high-density lipoprotein cholesterol (HDL-C) concentration among older adults and its contribution to the link between tooth loss and cognitive impairment. Methods: Data were retrieved from a public database, namely, the National Health and Nutrition Examination Survey (NHANES). Among 1,124 included participants who were aged above 60 years old, linear regression was performed to determine the association between tooth loss (moderate and severe tooth loss) and cognitive function [Consortium to Establish a Registry for Alzheimer's Disease-Immediate Recall (CERAD-IR), Delayed Recall (CERAD-DR), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST)]. Mediation analysis was used to test the effect of HDL-C on the association of tooth numbers and four cognitive tests. Results: Participants with moderate and severe tooth loss had lower scores on cognitive performance (p<0.001) and lower levels of HDL-C (p<0.05). The HDL-C levels were highly correlated with CERAD-IR and DSST, which mediated 2.11% to 5.24% of the total effect between tooth numbers and cognitive function. Conclusion: Tooth loss was negatively associated with cognitive function which was mediated by serum HDL-C levels. Clinical significance: Dentists should realize that the potential broader implications of tooth loss on overall well-being, including cognitive performance. The preservation of natural dentition might serve as a preventive measure against cognitive impairment, possibly mediated by abnormal lipid metabolism.