Dear Editor,
We read with interest the study by Winning et al. (2025) published in The Journal of Nutrition, Health and Aging [1]. Drawing upon 15 years of longitudinal data, the authors demonstrate a significant association between tooth loss (defined as having fewer than 20 natural teeth) and the incidence of mild cognitive impairment (MCI) and dementia. Moreover, they identify dietary diversity score (DDS) as a partial mediator in this relationship. We highly commend the methodological rigor of this study, particularly its valuable contribution to the interdisciplinary investigation of oral health and cognitive aging. Building upon these findings, we would like to offer several complementary reflections from the perspectives of structural determinants of health and modeling strategies.
First, in the current analysis, tooth loss is primarily modeled as a behavioral risk factor that compromises dietary intake and subsequently influences cognitive function. While this pathway is biologically plausible, it may underestimate the broader significance of tooth loss as a marker of cumulative social disadvantage. Oral health does not merely reflect present masticatory function, but embodies a long-term sedimentation of structural exposures - ranging from childhood nutrition and dental care access, to occupational hazards and healthcare availability [2]. Even after adjusting for educational attainment and material conditions, tooth loss remains significantly associated with MCI/dementia (Model 3 OR = 2.06), suggesting that its influence extends beyond nutritional pathways. Reframing tooth loss as a mediator - rather than merely a risk factor - between structural inequality and cognitive decline may better capture its role in the oral-cognition nexus.
Second, while a threshold-based approach to defining functional dentition is widely used in clinical and public health contexts [3], its dichotomization may oversimplify a socially patterned and continuous process. For instance, individuals with 10 and 19 teeth may differ significantly in oral function, yet are treated as equivalent exposures - potentially flattening gradients of disadvantage embedded in tooth loss. To better capture exposure variability and potential dose-response relationships, future studies might consider modeling tooth count as a continuous variable, using ordinal categories (e.g., 0–9, 10–19, 20+), or applying non-linear strategies such as restricted cubic splines for more flexible estimation. These approaches may yield a more nuanced understanding of how oral health disparities relate to cognitive outcomes over the life course.
Third, regarding covariate selection, the inclusion of denture use as a binary control variable reflects an important consideration of oral function. However, the actual functional benefit of dentures depends heavily on their stability, fit, wear habits, and masticatory efficiency. Prior research has shown that poorly fitting or infrequently used dentures may exacerbate dietary limitations and nutritional deficiencies [4], thereby accelerating cognitive decline. We suggest that future research expand the operationalization of denture-related variables to include functional satisfaction, self-reported chewing ability, and objective assessments such as the Masticatory Performance Index [5]. Such enhancements would enable more accurate identification of dentures’ potential moderating effects on diet and cognition.
In conclusion, this study provides robust empirical evidence linking oral health, dietary diversity, and cognitive decline, offering a valuable framework for interdisciplinary aging research and public health intervention. We sincerely thank the authors for their significant contribution to the field and look forward to future work that further elucidates the complex pathways connecting oral health, diet, and cognitive trajectories.
Declaration of Generative AI and AI-assisted technologies in the writing process
I have not used any AI at all.
Funding
There is no funding for this work.
Declaration of competing interest
The authors declare no competing interests.
References
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