Dental Status Is Unrelated to Risk of Dementia: A 20‐Year Prospective Study

Good dental status and oral health have been discussed in association with successful aging,1 cognitive functioning,2 and dementia.3 Whether the absence of natural teeth increases the risk of incident dementia was investigated in a large population-based sample of older adults (≥60 at baseline). A variety of demographic factors and apolipoprotein E (APOE) genotype were controlled for in the analyses. The data used in the present study emanate from the Betula prospective cohort study, established in Umeå, Sweden, in 1988.4 Baseline information about dental status was available for 2,120 participants aged 60 and older. Participants diagnosed with dementia were compared with those without over a follow-up period of up to 20 years. Those with dementia at baseline (n = 19), who were diagnosed with dementia shortly after the latest assessment (n = 10), or who died shortly after (<1 year) inclusion (n = 16) were discarded from the analyses. Thus, 2,075 participants were included in the analyses (917 men, 1,158 women). Their mean baseline age was 71.2 ± 8.2. Dental status was based on self-reports that divided the participants into three groups: only natural teeth (n = 1,110, mean age 68.5 ± 7.6; 52% female), natural teeth and dentures (n = 439, mean age 73.0 ± 7.7; 57% female), and edentulous and dentures (n = 526, mean age 75.5 ± 7.6; 63% female). Dementia was diagnosed using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition.5 A clinical and research geriatric psychiatrist performed the analyses, which covered 1989 to 2010.6 APOE genotyping was performed using polymerase chain reaction.7 Because it has been suggested that there might be a protective effect of the ε2 allele in relation to dementia,8 and because the ε4 is a risk factor,9 the combination of ε2/ε4 (n = 34) was not included in the analyses. Cox proportional hazards regression analysis was performed. First age, sex, and years of formal education were adjusted for (Model 1). Next, APOE ε4 allele status was added (Model 2). The same procedure was repeated for analyses of men and women, separately. Additional analyses were also performed following the same procedure but restricted to Alzheimer's disease (AD) as the outcome variable. The regional ethical vetting board at Umeå University approved this study (approval no. 04–169M, 08–132, 2012/12–31, 2013/92–31). Written informed consent was obtained from all participants. Over the follow-up period, 403 individuals developed dementia (n = 227 AD), and 1,672 remained dementia-free (n = 2,075). The results from the Cox proportional hazards regression analyses are presented in Table 1. In Model 1, adjusted for demographic variables, no significant hazard ratio (HR) was observed for the different dental status groups (natural and dentures: HR = 0.97, 95% confidence interval (CI) = 0.75–1.25; dentures: HR = 0.98, 95% CI = 0.77–1.25). Further adjustment for the APOE ε4 allele (Model 2) did not alter the results. Separate analyses for men and women did not change the outcome, and the same pattern was seen when only targeting AD. The current study investigated whether dental status (presence or absence of natural teeth) is a risk factor for dementia. Using a longitudinal design with a follow-up period of up to 20 years, the results did not corroborate earlier findings that dental status is a risk factor for dementia in general3 or for AD. A limitation of the current study is that dental status was assessed according to self-report. This method of obtaining dental data limits, to some extent, the validity of the current study, although 100 of the edentulous participants in the present population were randomly contacted in retrospect to verify dental status, and fewer than 5% of the self-reported data indicated any mismatch.10 A previous study found an association between dental status (number of natural teeth) and risk of dementia using self-reported data concerning dental status.3 The present study deviates from previous studies3 in that almost all of the individuals without natural teeth indicated that they used dentures; only four individuals without natural teeth did not have dentures. With the stated caveats in mind, the present findings strongly suggest that dental status is not a risk factor for dementia. The authors acknowledge the contribution by the staff in the Betula project. We also wish to thank the subjects for participating in the study. This work was supported by the Swedish Council for Social Research (Grant 421–2009–1268 to Jan Bergdahl). The Betula study is supported by the Swedish Council for Social Research (Grant 1988–1990: 88–0082, 311/1991–2000), the Swedish Research Council (Grant 345–2003–3883, 315–2004–6977), and the Knut and Alice Wallenberg Foundation. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Study design and conceptualization: Nilsson, Nyberg, Adolfsson, Bergdahl, Bergdahl. Statistical analyses: Hansson, Sörman. Interpretation of results and reviewing the manuscript: all authors. Drafting and revising manuscript: Hansson, Sörman. All authors approved the final manuscript. Sponsor's Role: None.