ABSTRACT
Objectives
This study aimed to determine the effectiveness of regular dental scaling by evaluating the association between the frequency of dental scaling and the risk of dementia in individuals with moderate to severe periodontal disease.
Methods
This study used the Korean National Health Insurance Service‐National Health Screening cohort database. Following the implementation of the dental scaling reimbursement policy, subjects were categorised into three groups based on the frequency of dental scaling. To enhance comparability of dementia risk across dental scaling frequency categories, we applied the inverse probability of treatment weighting method. Restricted cubic splines were utilised to examine hazard ratio trends for dementia. Landmark analyses were conducted to further strengthen the reliability of the results.
Results
In the Landmark analysis with follow‐up after 1 year, the adjusted hazard ratio was 0.51, and the inverse probability of treatment weighting hazard ratio was 0.40. In the Landmark analysis with follow up after 2 years, the adjusted hazard ratio was 0.50, and the inverse probability of treatment weighting hazard ratio was 0.39.
Conclusions
This study suggested that regular dental scaling in patients with moderate to severe periodontitis is associated with a reduced risk of dementia. In particular, changes in reimbursement policies are needed to ensure that underprivileged individuals with periodontal disease have access to regular dental scaling services.
Keywords: dementia, dental scaling, health policy, Korean National Health Insurance Service, periodontitis
1. Introduction
Dementia is characterised by cognitive decline that impairs daily functioning [1]. It is a broad term for mental decline, with Alzheimer's disease (AD) being the primary cause [2]. Aging is the primary risk factor for influencing dementia, making it a significant global health concern [3]. The World Health Organization projects that dementia cases will double by 2030 and triple by 2050 [4].
Dementia is a multifactorial neurodegenerative disorder with a complex aetiology [1]. Research encompasses its physical, social, and economic implications. Dementia presents with neurological and systemic manifestations. Its risk factors include genetic predisposition and environmental influences such as hypertension, diabetes, cerebrovascular disease, ischemic heart disease, and depression [5, 6]. Treatments strategies, including psychological intervention, antihypertensives, and statins, have demonstrated efficacy in managing dementia [7, 8, 9, 10]. Furthermore, advanced age and male sex are associated with increased severity of dementia and AD [11].
Chronic periodontitis is a multifactorial inflammatory disease resulting from dysbiotic dental biofilms [12]. Dental scaling, a fundamental periodontal therapy, effectively reduces clinical inflammation and pocket probing depth [13, 14]. To prevent the recolonisation of periodontal pathogens, regular removal of subgingival biofilms at patient‐specific intervals is essential. This underscores the importance of periodontal maintenance therapy, which involves subgingival debridement and/or scaling of pockets ≥ 4 mm deep [15].
Extensive research has identified poor oral health as a risk factor for dementia. Kusdhany et al. [16] demonstrated correlation between oral hygiene status and cognitive function, highlighting the potential impact of oral health on neurodegenerative decline. Similarly, Nadim et al. [17] compared dementia incidence between individuals with and without periodontitis, reporting that those with periodontitis had nearly twice the risk of developing dementia. A recent study has reported significant correlations between severe periodontal disease and AD prevalence [18]. Kim et al. [2] further indicated that the risk of developing dementia increases with the severity of periodontitis. Additionally, Yoo et al. [19] found that improved oral health care, including professional dental treatment and frequent tooth brushing, might reduce dementia risk associated with periodontal diseases. Their findings suggest that treating periodontitis could significantly lower dementia incidence.
Although previous studies have established an association between poor dental health and dementia, few have directly examined the impact of dental treatment on dementia onset. The evidence supporting a causal relationship between dental treatment and dementia remains limited, and the potential benefits of such interventions are not yet well understood. Beydoun et al. [20] examined the relationship between clinical periodontal markers and dementia incidence, suggesting that probing pocket depth contributes to AD development and that dental care could improve oral health in vulnerable elderly populations. However, their study did not account for the effects of improved dental hygiene on dementia prevention. While Yoo et al. [19] proposed that professional dental cleaning could modify dementia risk, their findings were based on comparisons between individuals who received professional cleaning and those who did not, leaving the impact of regular dental scaling on dementia prevention unclear. This study examines the effect of regular dental scaling on dementia incidence among patients with moderate to severe periodontitis, using population‐based retrospective cohort data from Korea.
2. Materials and Methods
2.1. Study Population
This study used data from the Korea National Health Insurance Service‐National Health Screening cohort (NHIS‐HEALS) database, which includes approximately 0.5 million individuals aged ≥ 40 years. These individuals represent 10% of randomly selected Koreans participating in NHIS health screening programs. To ensure representativeness, the sampling was stratified by sex, age, income level, and region. The NHIS‐HEALS database includes diagnoses based on the International Classification of Diseases, 10th revision (ICD‐10), and records of medical procedures and prescribed medications. Participants were monitored from January 1, 2002, to December 31, 2019.
In this study, patients with moderate to severe periodontal disease (n = 26,149) were selected in July 2013, when the dental scaling reimbursement policy was introduced, with the period before this designated as the washout phase. Following the implementation of this policy, patients were categorised into three groups based on the frequency of dental scaling: the regular group (frequency > 0.8), the occasional group (frequency between 0.3 and 0.8), and the infrequent group (frequency < 0.3). The final analysis included 10,971 participants in the regular group, 9610 in the occasional group, and 5589 in the infrequent group. To enhance the reliability of dementia risk assessment, landmark analysis was performed at 1 year (regular group = 10,702; occasional group = 9559; infrequent group = 5555) and 2 years (regular group = 10,308; occasional group = 9482; infrequent group = 5531) after the implementation of the dental scaling reimbursement policy (Figure 1).
FIGURE 1.
The flow of study population.
2.2. Definition of Moderate to Severe Periodontal Disease
The number of periodontitis‐related dental procedures was identified using ICD‐10 diagnostic codes for periodontal disease (K05) from January 2014 to January 2015. Treatment codes for patients with moderate to severe periodontal disease included subgingival curettage (U1010), tooth extraction (U4412), periodontal flap surgery (U1051, U1052), bone grafting for alveolar bone defects (U1071, U1072), and guided tissue regeneration (U1081–U1083) (Table S1) [2].
2.3. Outcome
The NHIS defined dementia based on ICD‐10 codes F00, F01 and F03. Patients were classified as having dementia if they had at least one hospital admission or two or more outpatient visits (Table S1) [2].
2.4. Variables
To analyze the baseline characteristics of the study population, clinical variables were extracted from the NHIS database based on the date of the first periodontitis‐related procedure for each participant. The extracted variables included demographics (sex, age, income level, and residential area) and major non‐communicable diseases, such as hypertension (I10, I11), diabetes (E10–E14), dyslipidemia (E78), cerebrovascular disease (I60–I69), myocardial infarction (I21, I22), and depression (F32, F33) using ICD‐10 codes. The Charlson Comorbidity Index (CCI) was used to assess the burden of comorbidities [21] based on pre‐existing conditions within 1 year using ICD‐10 codes (Table S1).
2.5. Statistical Analysis
Variables are presented as means with standard deviations or frequencies with percentages. Differences in covariates among the three groups were assessed using the analysis of variance and chi‐square tests. The incidence rate of dementia was expressed per 1000 person‐years for each group over the follow‐up period.
To analyse dementia risk, Kaplan–Meier survival curves were generated, and differences between groups were evaluated using the log‐rank test. The Cox proportional‐hazards model was employed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for dementia risk. This model was adjusted for covariates, including age, sex, income level, residential area, hypertension, diabetes, dyslipidaemia, cerebrovascular disease, myocardial infarction, depression, and CCI. For subgroup analysis, participants were stratified by sex and age. To enhance comparability in dementia risk across the frequency categories of dental scaling, the inverse probability of treatment weighting (IPTW) method was applied [22]. Propensity scores were calculated using a multinomial logistic regression model, incorporating all measured covariates to determine the probability of assignment to each group. IPTW analysis was then performed to balance covariates across the three groups, with the Infrequent group (frequency < 0.3) serving as the reference. The analyses were repeated after IPTW weighting, and results were reported as HRs and 95% CIs. Additionally, restricted cubic splines were used to assess HR trends and their 95% CIs for dementia risk based on dental scaling frequency.
The landmark method was applied in this study to mitigate potential biases in assessing the association between dental scaling frequency and dementia incidence. This method involves establishing arbitrary landmark points and analysing only those participants who were exposed to a drug or treatment after these points while classifying others into non‐exposure groups [23]. Participants who experienced an event before the landmark time were excluded from the analysis to prevent misclassification related to individual time frames. Additionally, this approach reduces the risk of confounding by minimising collider bias, which might arise when selecting individuals based on survival‐related factors [24, 25]. For this study, landmark points were set at 1‐year and 2‐year intervals. All statistical analyses were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) and R version 4.3.0 (R Foundation for Statistical Computing, Vienna, Austria). Statistical significance was set at p < 0.05.
2.6. Ethics Statement
This study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines [26]. Additionally, it complied with the ethical principles of the Declaration of Helsinki for research involving human participants and human data [27]. Given its retrospective design and the use of anonymous claims data, the requirement for informed consent was waived. Ethical approval was obtained from the Institutional Review Board of Youngsan University (YSUIRB‐202408‐HR‐160‐02).
3. Results
3.1. Demographic Characteristics by Frequency of Dental Scaling
The study included 26,149 individuals with moderate to severe chronic periodontitis. Table 1 presents the baseline characteristics of the study population, categorised into three groups based on dental scaling frequency. Among them, 5568 individuals were in the regular group (frequency > 0.8), 9610 individuals were in the occasional group (frequency between 0.3 and 0.8), and 10,971 individuals were in the infrequent group (frequency < 0.3). With increasing frequency of dental scaling, the mean age of the participants decreased, while the proportion of individuals with higher income levels and urban residence increased. In contrast, the prevalence of underlying conditions such as hypertension, diabetes, cerebrovascular disease, myocardial infarction, and depression was higher among individuals with lower scaling frequency. Additionally, the CCI decreased as the scaling frequency increased. The mean scaling frequencies in the three groups were 0.1 ± 0.1, 0.4 ± 0.1, and 0.9 ± 0.1, respectively (Table 1).
TABLE 1.
Baseline characteristics of study population.
| Variable | Infrequent group (n = 10,971) | Occasional group (n = 9610) | Regular group (n = 5568) | p | |
|---|---|---|---|---|---|
| Sex (%) | Male | 5703 (52.0) | 5069 (52.7) | 2928 (52.6) | 0.52 |
| Female | 5268 (48.0) | 4541 (47.3) | 2640 (47.4) | ||
| Age (years) | Mean (SD) | 65.5 (9.5) | 61.9 (7.6) | 60.7 (6.8) | < 0.001 |
| Income level (%) | 1st quartile | 1891 (17.2) | 1494 (15.5) | 787 (14.1) | < 0.001 |
| 2nd quartile | 2499 (22.8) | 2019 (21.0) | 1041 (18.7) | ||
| 3rd quartile | 3338 (30.4) | 2859 (29.8) | 1496 (26.9) | ||
| 4th quartile | 3243 (29.6) | 3238 (33.7) | 2244 (40.3) | ||
| Residence (%) | Rural | 5077 (46.3) | 3359 (35.0) | 1455 (26.1) | < 0.001 |
| Urban | 5894 (53.7) | 6251 (65.0) | 4113 (73.9) | ||
| Hypertension (%) | 6026 (54.9) | 4459 (46.4) | 2436 (43.8) | < 0.001 | |
| Diabetes (%) | 1980 (18.0) | 1324 (13.8) | 659 (11.8) | < 0.001 | |
| Dyslipidemia (%) | 4229 (38.5) | 3596 (37.4) | 2146 (38.5) | 0.20 | |
| Cerebrovascular accident (%) | 1551 (14.1) | 918 (9.6) | 502 (9.0) | < 0.001 | |
| Myocardial infarction (%) | 405 (3.7) | 312 (3.2) | 157 (2.8) | 0.010 | |
| Depression (%) | 2827 (25.8) | 2288 (23.8) | 1313 (23.6) | 0.001 | |
| Charlson comorbidity index (%) | 0 | 3808 (34.7) | 3721 (38.7) | 2178 (39.1) | < 0.001 |
| 1 | 2734 (24.9) | 2522 (26.2) | 1540 (27.7) | ||
| 2 | 1784 (16.3) | 1564 (16.3) | 894 (16.1) | ||
| ≥ 3 | 2645 (24.1) | 1803 (18.8) | 956 (17.2) | ||
| Ratio | Mean (SD) | 0.1 (0.1) | 0.4 (0.1) | 0.9 (0.1) | < 0.001 |
3.2. Restricted Cubic Spline Analysis of the Association Between Dental Scaling Frequency and Dementia
A restricted cubic spline analysis was conducted to visualise the linear relationship between HR for dementia and dental scaling frequency among patients with moderate to severe periodontitis. The analysis revealed a decreasing trend in dementia risk with increasing scaling frequency (Figure 2). In the spline plot, the blue line represents the HR, while the shaded region depicts the 95% CIs for dementia incidence. The horizontal dotted line indicates the reference HR of 1.0, and a dental scaling frequency of 0.4 was selected as the reference point.
FIGURE 2.
Restricted cubic spline of hazard ratio with 95% confidence intervals for dementia.
3.3. Dementia Risk Comparison Based on Dental Scaling Frequency
Among the 26,149 study participants, dementia cases were most common in the infrequent group (922 cases), followed by the occasional group (324 cases), and the regular group (94 cases). The incidence rate (per 1000 person‐years) was lower in the regular group (3.44) compared to the occasional group (6.95). The crude HRs for dementia, relative to the infrequent group, were 0.19 (95% CI, 0.16–0.24) for the regular group and 0.39 (95% CI, 0.35–0.45) for the occasional group. The adjusted HRs were 0.52 (95% CI, 0.41–0.64) for the regular group and 0.78 (95% CI, 0.68–0.89) for the occasional group. The IPTW HRs were 0.42 (95% CI, 0.36–0.49) and 0.68 (95% CI, 0.61–0.77) for the regular and occasional groups, respectively.
Landmark analyses further supported these findings. After 1 year of follow‐up, among 25,816 participants, 765 cases of dementia were observed in the infrequent group, 274 in the occasional group, and 81 in the regular group. Dementia incidence remained lowest in the regular group (2.96 per 1000 person‐years) compared to the occasional group (5.88 per 1000 person‐years). The crude HR for the regular group was 0.20 (95% CI, 0.16–0.25), the adjusted HR was 0.51 (95% CI, 0.40–0.65), and the IPTW HR was 0.40 (95% CI, 0.34–0.47).
Similarly, after 2 years of follow‐up, among 25,321 participants, 520 cases of dementia were observed in the infrequent group, 207 in the occasional group, and 57 in the regular group. The incidence rate was 2.09 per 1000 person‐years in the regular group versus 4.46 per 1000 person‐years in the occasional group. The crude HR for dementia in the regular group was 0.21 (95% CI, 0.16–0.27), the adjusted HR was 0.50 (95% CI, 0.38–0.67), and the IPTW HR was 0.39 (95% CI, 0.32–0.48) (Table 2).
TABLE 2.
Association between ratio and dementia.
| Group | Number | Events | Follow‐up duration (person‐years) | Incidence rate (per 1000 person‐years) | Crude HR (95% CIs, p) | Adjusted HR (95% CIs, p) | IPTW HR (95% CIs, p) |
|---|---|---|---|---|---|---|---|
| Infrequent group | 10,971 | 922 | 52,256 | 17.64 | 1 (Reference) | 1 (Reference) | 1 (Reference) |
| Occasional group | 9610 | 324 | 46,600 | 6.95 | 0.39 (0.35–0.45, p < 0.001) | 0.78 (0.68–0.89, p < 0.001) | 0.68 (0.61–0.77, p < 0.001) |
| Regular group | 5568 | 94 | 27,362 | 3.44 | 0.19 (0.16–0.24, p < 0.001) | 0.52 (0.41–0.64, p < 0.001) | 0.42 (0.36–0.49, p < 0.001) |
| Landmark analysis (follow up after 1 year) | |||||||
| Infrequent group | 10,702 | 765 | 52,099 | 14.68 | 1 (Reference) | 1 (Reference) | 1 (Reference) |
| Occasional group | 9559 | 274 | 46,567 | 5.88 | 0.40 (0.35–0.46, p < 0.001) | 0.77 (0.66–0.88, p < 0.001) | 0.67 (0.59–0.76, p < 0.001) |
| Regular group | 5555 | 81 | 27,355 | 2.96 | 0.20 (0.16–0.25, p < 0.001) | 0.51 (0.40–0.65, p < 0.001) | 0.40 (0.34–0.47, p < 0.001) |
| Landmark analysis (follow up after 2 years) | |||||||
| Infrequent group | 10,308 | 520 | 51,487 | 10.10 | 1 (Reference) | 1 (Reference) | 1 (Reference) |
| Occasional group | 9482 | 207 | 46,445 | 4.46 | 0.45 (0.38–0.52, p < 0.001) | 0.83 (0.70–0.98, p = 0.03) | 0.73 (0.62–0.85, p < 0.001) |
| Regular group | 5531 | 57 | 27,318 | 2.09 | 0.21 (0.16–0.27, p < 0.001) | 0.50 (0.38–0.67, p < 0.001) | 0.39 (0.32–0.48, p < 0.001) |
Note: The model was adjusted for age, sex, income level, residence, hypertension, diabetes, dyslipidemia, cerebrovascular accident, myocardial infarction, depression, and Charlson comorbidity index.
The Kaplan–Meier survival analysis demonstrated a significantly higher disease‐free probability in the regular group compared to the occasional group. The log‐rank test confirmed this difference, yielding a statistically significant p‐value of 0.0001. Additionally, landmark analyses with follow‐up periods of 1 and 2 years revealed that disease‐free probability remained higher in the regular group compared to the occasional group, as depicted by the Kaplan–Meier curves. Both analyses produced a statistically significant p‐value of 0.0001 (Figure 3).
FIGURE 3.
Kaplan–Meier curve for the association between ration and dementia.
3.4. Subgroup Analysis According to Sex and Age
The subgroup analysis by age categorised participants into two groups: ≥ 65 years and < 65 years. In both age groups, the incidence of dementia was lower in the regular scaling group compared to the occasional group. The adjusted HR for dementia incidence in the regular group, relative to the infrequent group, was 0.55 (95% CI, 0.43–0.69) for individuals aged ≥ 65 years and 0.38 (95% CI, 0.21–0.69) for those aged < 65 years. Similarly, in the subgroup analysis by sex, dementia incidence was lower in the regular group than in the occasional group for both males and females. The adjusted HR for dementia incidence in the occasional group, compared to the infrequent group, was 0.67 (95% CI, 0.53–0.83) for males and 0.84 (95% CI, 0.71–0.99) for females. In the regular group, the adjusted HR for dementia was 0.38 (95% CI, 0.26–0.55) for males and 0.61 (95% CI, 0.47–0.80) for females (Figure 4).
FIGURE 4.
Subgroup analysis for association between dental scaling and dementia.
4. Discussion
Periodontitis is a highly prevalent chronic disease, affecting 10% to 60% of adults worldwide [28], with severe cases accounting for approximately 10% of the global population [29]. Despite numerous studies suggesting a potential link between dental health and dementia, the evidence remains inconclusive [16, 30]. This study is the first to confirm that regular dental scaling significantly reduces the risk of dementia among individuals with moderate to severe periodontitis in the Korean population. This study analysed 26,149 participants with moderate to severe periodontitis to evaluate the association between regular dental scaling and dementia risk, using data from the NHIS‐HEALS cohort in Korea. Participants were categorised into three groups based on the frequency of dental scaling. The regular group had an average frequency of 0.9, equivalent to undergoing scaling approximately once a year. The occasional group had an average frequency of 0.4, corresponding to scaling approximately once every 2 years, while the infrequent group had an average frequency of 0.1, indicating rare dental scaling.
In this study, the Cox proportional‐hazards model demonstrated a significantly higher risk of dementia among individuals who underwent dental scaling less frequently. The Kaplan–Meier curve further revealed significant differences in disease‐free survival across the three groups, with the regular group exhibiting the highest likelihood of remaining disease‐free (Figure 3A). Additionally, restricted cubic spline analysis indicated that when the scaling frequency was < 0.4, all 95% CI values exceeded 1 (Figure 2). These findings underscore the importance of undergoing dental scaling at least once every 2 years to mitigate dementia risk. Supporting this, Chen et al. [31] analysed national data from Taiwan and reported that patients with periodontitis who did not undergo scaling within 3 years had a 1.22 fold higher risk of developing dementia than those without periodontitis, emphasising the significance of regular dental scaling. Consistent with these findings, our results indicate that compared to the infrequent group, the occasional group had a reduced dementia risk by 0.78 (adjusted HR) and 0.68 (IPTW HR), while the regular group demonstrated an even lower risk, with an adjusted HR of 0.52 and IPTW HR of 0.42, respectively (Table 2).
Dementia typically develops over 5 to 20 years, making it challenging to establish an immediate causal relationship between dental scaling and dementia onset [32]. To address this, 1‐ and 2‐year landmark analyses were implemented, excluding individuals diagnosed with dementia or periodontal disease before the introduction of the scaling reimbursement policy, to assess the subsequent risk of dementia. Our findings indicate that after a year, the regular scaling group had up to 51% lower adjusted HR and up to 40% lower IPTW HR than the infrequent group (Table 2, Figure 3B). After 2 years, the risk reduction remained significant, the regular scaling group had up to 50% lower adjusted HR and up to 39% lower IPTW HR than the infrequent group. (Table 2, Figure 3C). Notably, even with a 2‐year follow‐up, regular dental scaling continued to demonstrate a significant protective effect against dementia. These results highlight not only the direct effect of plaque and calculus removal through scaling but also the indirect benefits of ongoing exposure to oral health education. Similarly, Yoo et al. [19] reported that professional dental cleaning reduced dementia risk by 0.91, while frequent tooth brushing lowered the risk by 0.83, further emphasising the crucial role of consistent oral hygiene management in dementia prevention.
Subgroup analyses by sex and age demonstrated that regular dental scaling was more effective in reducing dementia risk among men and individuals aged < 65 years (Figure 4). This aligns with previous research indicating that women are at a higher risk of developing dementia than men [33, 34]. Therefore, in men—who generally have a lower incidence of dementia—regular dental scaling might provide a more pronounced preventive effect. Aging remains the primary risk factor for dementia, with prevalence rates reaching 37.4% in individuals aged 70–79 years and 34% in those aged 80–89 years [31]. Given this, implementing periodontal disease management through regular dental scaling earlier in life, rather than after the onset of old age, might contribute to a lower dementia risk over time.
Regular dental scaling has been shown to reduce the risk not only of dementia but also of cardiovascular disease [35] and spontaneous intracranial haemorrhage [36], underscoring the importance of annual dental scaling. In South Korea, a dental scaling reimbursement policy covers 70% of the cost for one annual, and the number of beneficiaries has been gradually increasing [13]. Our analysis of socio‐demographic characteristics revealed that individuals in the infrequent scaling group were older, had lower incomes, resided in rural areas, and exhibited a higher prevalence of comorbidities (Table 1). These findings align with previous research, confirming the effectiveness of the dental scaling reimbursement policy in Korea [37]. However, despite the significant rise in scaling use since the implementation of the 2013 policy, disparities in access to insurance benefits persist for certain demographic groups [13]. To enhance the benefits of dental scaling among vulnerable populations, targeted interventions might be necessary, such as increasing reimbursement frequency for individuals with systemic diseases or adjusting coverage levels based on income.
This study has several limitations. First, as the analysis relied on NHIS‐HEALS data, discrepancies might exist between actual treatment practices and insurance claims. Additionally, non‐covered dental scaling procedures could not be accounted for, potentially leading to variations in the frequency of scaling. Second, since the study included patients with moderate to severe periodontitis, many might have undergone additional periodontal treatments alongside scaling during the follow‐up period. However, given that scaling is a prerequisite for other periodontal treatments, it remains a critical factor in slowing or halting periodontitis progression. The primary objective of this study was to assess the association between regular dental scaling and dementia risk. Future research will aim to analyse dementia risk across all patients with periodontal disease, distinguishing between those with healthy, cured, and ongoing periodontal conditions. Third, despite adjustments for multiple confounding factors, some unaccounted variables might still influence the results. For instance, lifestyle factors such as smoking and alcohol consumption, which could affect dementia risk, were not adjusted for. Nonetheless, various comorbidities were adjusted and IPTW was applied to enhance group homogeneity. Fourth, residual confounding due to physician's treatment decisions and unmeasurable factors remains a limitation of observational studies. Thus, the findings should be interpreted as associations rather than causal relationships. Lastly, although landmark analysis classifies individuals into exposure groups only after a defined period, it does not eliminate selection bias, as those surviving until the landmark time point might differ systematically from those who do not. Despite these limitations, this study is the first to confirm an association between regular dental scaling and reduced dementia risk in patients with moderate to severe periodontitis. To increase the reliability of the findings, the study focused on patients with moderate to severe periodontitis and applied landmark analysis at 1‐ to 2‐year intervals following scaling. These results suggest that improving periodontal health through regular dental scaling might contribute to a reduced risk of dementia in patients with moderate to severe periodontitis.
5. Conclusion
Using the NHIS‐HEALS database of Korea, this study provides compelling evidence that regular dental scaling in patients with moderate to severe periodontitis is significantly associated with a reduced risk of developing dementia. This study highlights the need for policy adjustments that address the needs of underprivileged populations, thereby enhancing the effectiveness of dental scaling reimbursement policies. Additionally, future well‐designed prospective studies are essential to comprehensively evaluate the long‐term impact of regular dental scaling on dementia risk.
6. Clinical Relevance
6.1. Scientific Rationale for the Study
Many studies have already revealed the relationship between periodontal disease and dementia. In comparison, there is very little evidence on the relationship between regular dental scaling to prevent periodontal disease and dementia.
6.2. Principal Findings
Our findings confirm that patients with moderate–severe periodontitis have a lower risk of developing dementia if they undergo regular dental scaling.
6.3. Practical Implications
Since the relationship between regular dental scaling and dementia has been confirmed, oral examinations and regular dental scaling to prevent periodontitis will be necessary to reduce the incidence of dementia.
Author Contributions
Conceptualisation, Minkook Son, Seon‐Rye Kim and Yu‐Rin Kim have made substantial contributions to the conception and design of the study. Minkook Son, Seon‐Rye Kim and Yu‐Rin Kim have been involved in data collection. Minkook Son and Seon‐Rye Kim have been involved in data interpretation, drafting the manuscript Minkook Son, Yu‐Rin Kim and Seon‐Rye Kim have been reviewed the data and revising it critically. All authors have given final approval of the version to be published have been reviewed the data and drafted the manuscript.
Funding
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS‐2024‐00342613), by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (RS‐2025‐02223073).
Ethics Statement
This study was approved by the Institues Ethics Board of Youngsan University (IRB No. YSUIRB‐202408‐HR‐160‐02) conducted in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) and waived the need for the informed consent.
Consent
This study was retrospective and used anonymous claims data. Therefore, consent was not required to provide information.
Conflicts of Interest
The authors declare no conflicts of interest.
Supporting information
Table S1: Definitions of diseases by disease classification codes and insurance claim codes.
Acknowledgements
The authors have nothing to report.
Data Availability Statement
The data that support the findings of this study are openly available in National Health Insurance Data Sharing Service at https://nhiss.nhis.or.kr/en/z/a/001/lpza001m01en.do.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1: Definitions of diseases by disease classification codes and insurance claim codes.
Data Availability Statement
The data that support the findings of this study are openly available in National Health Insurance Data Sharing Service at https://nhiss.nhis.or.kr/en/z/a/001/lpza001m01en.do.