Association Between Statin use and Chronic Periodontitis: A Longitudinal Follow-Up Study using Korean National Health Screening Cohort

Background: Since potential link between statin and the risk of adverse chronic periodontitis (CP) has been raised, we aimed to validate the associations of statin use on the incidence of CP using a nationwide cohort data. Methods: This longitudinal follow-up study included 169,381 patients who were administered statins matched with an equal number of controls using propensity score from the Korean National Health Insurance Service-Health Screening Cohort database (2002–2015). A Cox proportional hazard model was used to assess the occurrence of CP following statin use after adjusting for multiple covariates. Results: The occurrence of CP was signicantly higher with long-term use (1–3 years, 3–5 years, or >5 years) than with short-term use ( ≤ 1 year). After adjustment, statin users exhibited a 1.32-fold higher occurrence of CP (95% condence interval=1.30–1.33) than the matched non-users (incidence: 25.0 and 22.0 per 100 person-years, respectively). Subgroup analyses supported the adverse impact of statins on CP independent of age and sex. Conclusions: Statin use in individuals aged >40 years, of both sexes, may slightly increase the risk of occurrence of CP, especially with long-term use, warranting a caution regarding the onset of CP as a possible adverse effect of long-term statin use.


Introduction
Statins are the most widely used lipid-lowering agents for treating hypercholesterolemia and cardiovascular disease. They inhibit 3-hydroxy-3 methylglutaryl-coenzyme A (HMG-CoA) reductase and statin therapy is generally considered safe and well-tolerated 1 . Statins e ciently suppress low-density lipoprotein cholesterol levels and have pleiotropic effects of systemic anti-in ammatory activity including locally atherosclerotic plaques and enhancing antimicrobial and fungicidal activities and bone modulation [1][2][3][4] . Considering these bene ts, many studies had suggested that statins have the supplemental clinical bene ts of reducing periodontal in ammation and preventing alveolar bone loss in periodontitis 5,6 ; other studies reported contradictory results [7][8][9][10] .
Chronic periodontitis (CP) is a multifactorial infectious in ammatory disease closely related to the host immune system and environmental risk factors 11 . It is characterized by immune-in ammatory in ltration of the deeper compartments of the periodontium, resulting in destruction of the tooth-supporting tissues such as cementum, periodontal ligament, and alveolar bone and impaired masticatory function, which culminates in tooth loss and negatively impacts quality of daily life 12,13 . CP is highly prevalent among the elderly, who are often prescribed statins to control cardiovascular disease 14 ; this highlights the signi cance of exploring the effects of statins in periodontitis. Orally administered statins were reported to improve healing outcomes and decreased in ammatory activity in experimental periodontitis in rat models and patients with CP undergoing treatment 2,5,15−18 . Local administration of statins, adjunctive to non-surgical/surgical periodontal treatment, was also effective in preventing alveolar bone loss in clinical and animal studies of periodontitis 6, 19 . Nevertheless, its safety has not been fully elucidated in the short-and long-term with regard to CP.
Risk of unexpected adverse events related to the statin use has been reported in the last two decades, raising safety concerns regarding statin therapy 4,20 . The mechanism underlying these observations remains unclear.
Recent systematic reviews have reported statins to be safe therapeutic agents in improving oral health 12,21 . Most of the previous clinical and animal studies focused on the relatively short-term effects of statins on the severity of pre-existing periodontitis and had limited sample sizes 6-8, 15,18 . Research has been scarce on the long-term effects of statin on large cohorts of patients with CP. Alghofaily et al. 16 demonstrated higher healing outcomes in patients with periodontitis on statins for long periods compared with controls; however, the duration of statin intake was not clearly described, and the groups were not age or sex matched. Therefore, longitudinal studies on different populations and with large sample sizes are needed to con rm the relationship between statins and clinical outcomes in CP.
Based on these evidences, we hypothesized that long-term and short-term statin use might have different effects in CP. A longitudinal follow-up study using a nationwide, population-based cohort among Korean adults was carried out to estimate the potential impact of statins on periodontitis-related outcomes depending on the duration of statin intake.

Participant Selection
This study was approved by the ethics committee of Hallym University (approval number 2019-10-023) and the requirement for written informed consent was waived by the institutional review board and performed in accordance with the relevant guidelines and regulations (Declaration of Helsinki).
The present was conducted retrieved from information from the Korean National Health Insurance Service-Health Screening (KNHIS-HS) database, which offers population-based electronic les for research purposes that were deidenti ed in the identi cation codes with anonymous information of the Korean population, as previously described 22 . The diagnostic codes of the KNHIS-HS data follow the International Classi cation of Diseases, 10th Revision, Clinical Modi cation (ICD-10-CM). From a total of 514,866 individuals with 615,488,428 medical claim codes (from 2002 to 2015), those who rst had statin prescriptions for a minimum of 6 months were included in the statin-user group (n = 192,296), while others who had never prescribed statins were included in the control group (n = 322,570). We excluded the statin users from 2002 to 2003 (n = 17,670), as we included pre-existing CP before the index date in the analysis. Further, we excluded patients who did not have total cholesterol records (n = 68), blood pressure records (n = 23), fasting blood glucose records (n = 6), or body mass index (BMI, kg/m 2 ) records (n = 6) from the statin user group.
In the control group, we excluded 1,474 individuals who either died before 2004 or had no records since and 23,650 patients who received a single prescription of statins from 2002 to 2015.
The statin-user group was matched 1:1 with the control group by means of propensity-score matching through logistic regression for age, sex, income, and region of residence. To avoid any selection bias, statin non-users were extracted according to a random number order. The index date of each statin user was de ned as the rst date of statin prescription. The index date of control group was determined as the index date of their matched statin users. During the matching process, 128,065 control group and 5,142 statin users were excluded. Finally, 169,381 statin users were matched with 169,381 control group in 1:1 ratio for the study, and then the risk of CP was analyzed as the primary objective.
The statin-user group was subcategorized according to the duration of statin use as: ≤1 year (n = 57,791), >1 year to ≤3 years (n = 47,117), >3 years to ≤5 years (n = 29,176), and >5 years (n = 35,297). The risk of CP was analyzed among them as the secondary objective. Figure 1 summarizes the ow illustration of the study population enrollment.

Independent variable (statin prescription)
Statin prescription was considered the independent variable. The date on which statins were rst prescribed was de ned as the index date, and subsequent statin use data was analyzed. Statin-user group was con gured as patients who were prescribed statins for a minimum of 6 months between 2002 and 2015. The patients deemed short-term users as 6 months-1 year prescription, as previously described. 23 Dependent variable (chronic periodontitis) CP was considered the dependent variable. Diagnosis of CP according to ICD-10 code (K05.3: Chronic periodontitis) and treatment by dentists was analyzed.

Covariates
Participants were classi ed according to age into 10 groups of 5-year intervals: from 40-44 years to >85 years, according to income into ve classes (class 1 [lowest]-class 5 [highest]), according to regions of residence into urban and rural provinces, based on the previous study 24 . Tobacco smoking, alcohol consumption, and obesity (BMI [body mass index], kg/m 2 ) were subdivided as described in our previous study 24 . Dyslipidemia was considered as treatment history with two or more times due to diagnosis with dyslipidemia according to ICD-10 code (E78). Fasting blood glucose level (mg/dL), systolic blood pressure (SBP, mmHg), diastolic blood pressure (DBP, mmHg), and total cholesterol level (mg/dL) were obtained. The number of previous diagnoses of CP before the index date was determined. The Charlson Comorbidity Index (CCI) score was calculated, which is widely applied to quantify disease burden using seventeen comorbidities, as the continuous variable (0 [no comorbidities] to 29 [multiple comorbidities]) 25 .

Statistical Analyses
Differences between study and control groups were adjusted through propensity-score matching calculated by logistic regression with aforementioned four baseline covariates using greedy option of nearest-neighbor matching algorithm 26 . After matching, balance between groups was evaluated again. Categorical data were summarized with numbers and percentages. Continuous data were depicted as mean and standard deviation. Characteristics between the statin user and control groups were compared using the chi-square test for categorical variables and the independent t-test or one-way analysis of variance (ANOVA) for continuous variables.
To analyze the hazard ratio (HR), with 95% con dence interval (CI), for CP (primary objective) between statin user and control groups, a strati ed Cox proportional hazard model was applied; crude and adjusted models (adjusted for fasting blood glucose, alcohol consumption, obesity, dyslipidemia history, total cholesterol, smoking, SBP, DBP, the number of preexisting CP, and CCI scores) were calculated. The analysis was strati ed according to age, sex, areas of residence, and income. For the further subgroup analyses, participants were subdivided according to age (<60 and ≥60 years old) and sex (men and women) and both the crude and adjusted models were analyzed.
To analyze the HR, with 95% CI, for CP among the duration of statin use (secondary objective), an unstrati ed cox proportional hazard method was performed. In this analysis, crude model 1 (adjusted for fasting blood glucose, CCI scores, obesity, smoking, total cholesterol, alcohol consumption, SBP, and DBP), and model 2 (dyslipidemia history and the number of previous CP diagnoses added to model 1) were calculated.

Baseline characteristics
The study comprised 169,381 patients with history of statin use and those equivalent numbers of matched controls were retrieved from the database. The average duration from January 1, 2002 to CP diagnosis was 454,036 person-years in the statin user group and 484,893 person-years in the control group. Age, region of residence, sex, and income were evenly matched between the two groups (P = 1.000; Table 1). Development of new CP during the study period was higher in the statin user group (66.9% [113,349 of 169,381]) than in the control group (62.9% [106,562 of 169,381]) (P<0.001). Compared with the controls, statin users were more likely to have dyslipidemia, obesity, smoking habit, comorbidities, frequent alcohol consumption (≥1/week), and higher total cholesterol or fasting glucose level, or hypertension (P<0.001).

Characteristics of statin users according to the duration of use
Participants in the statin user group aged between 50 to 70 years were than other age groups (P<0.001) ( Table  2). Women tended to use statins for a longer durations than men (P<0.001). Long-term statin users (>5 years) tended to have higher income, were more likely to be from an urban region, obese (BMI 25-30), non-smokers, or consumed less alcohol (less than once a week), and had more comorbidities than short-term users (≤1 year) (P<0.001). Blood pressure, fasting blood glucose level, and total cholesterol level were the highest among those who used statins for >5 years (all P<0.001). The rate of pre-existing periodontitis decreased with increased duration of statin use (P<0.001), while the incidence of dyslipidemia and subsequent CP tended to increase with an increase in duration (1-3 years, 3-5 years, or >5 years) compared to short-term duration (≤1 year) (each P<0.001).  * Strati ed Cox proportional hazard model, Signi cance at P < 0.05 † Models were strati ed by age, sex, income, and region of residence. ‡ Adjusted for dyslipidemia history, total cholesterol, systolic blood pressure, diastolic blood pressure, fasting blood glucose, obesity, smoking, alcohol consumption, the number of previous CP, and CCI scores.
The incidence of CP during the study period was higher in statin users than in control group in all age and sex subgroups. In subgroup analyses, statin use was consistently associated with a high likelihood of having  (Table 4). However, the HRs were slightly reduced in the group with >5 years of statin use compared to durations of 3-5 years or 1-3 years (P for trend = 0.002). Abbreviations: FU, Follow-up duration; IR, Incidence rate per 100 person-years; CCI, Charlson comorbidity index; CP, chronic periodontitis.
* Un-strati ed Cox proportional hazard model, Signi cance at P < 0.05 † A model 1 was adjusted for total cholesterol, systolic blood pressure, diastolic blood pressure, fasting blood glucose, obesity, smoking, alcohol consumption, and CCI scores. ‡ A model 2 was adjusted for model 1 plus dyslipidemia history and the number of previous CP.

Discussion
Using a nationwide and large-scale cohort data, this longitudinal follow-up study demonstrated that both men and women aged over 40 years who use statins have an increased likelihood of newly occurring CP compared with matched controls. Among long-term statin users, pre-existing periodontitis was low while newly occurring periodontitis was high. The relation between statin use and increased likelihood of CP occurrence remained signi cant even after adjustment for confounders, indicating that statin use was independently involved in an increased tendency to develop CP.
Large-scale nationwide studies are scarce on the relationship between statin use and CP risk based on duration of use. Among the 338,762 participants aged ≥40 years, those receiving statin exhibited a 1.32-fold higher chance for developing CP (95% CI 1.30-1.33) than matched control participants (incidence: 25.0% and 22.0% per 100 person-years, respectively). Although the magnitude of risk is low, statin use may slightly increase the risk of developing CP. Long-term statin users (1-3 years, 3-5 years, or >5 years) had a higher risk for CP than short-term users (≤1 year). Pre-existing periodontitis decreased in long-term statin users compared to shortterm users, implying that statins may likely be effective in decreasing pre-existing periodontitis but adversely effects newly occurring periodontitis. Decrease in pre-existing CP during the 5-year period is partly in line with results from a prospective double-blind, randomized study among 83 participants conducted in USA, which demonstrated that 12 week-therapy of statin markedly reduced periodontitis 5 . The trend of reduction in periodontitis was perceived in rst 28 days after initiation of statin intake 5 . An epidemiologic study reported that the use of any statin is associated with a 48% decrease in CP-related tooth loss in the initial three years, which may suggest that statins possess anti-in ammatory and bone modulating features during the rst several years that may positively in uence pre-existing CP 17 .
Conversely, literature is still scarce to support our ndings on increased risk of CP occurrence due to statin therapy among long-term users. The accuracy of the present data is supported by the similar clinical characteristics of statin users with respect to obesity, smoking, increased comorbidities, alcohol drinking, or dyslipidemia, and high total cholesterol, blood pressure, or fasting glucose level, as reported in previous studies 1,4,5,16,20 . This may be because most of the previous studies focused on the relatively short-term effects of statins on the in ammatory parameters of pre-existing periodontitis. In a previous study 2 , it was mentioned that subsequent 15 periodontitis among 29 patients with hyperlipidemia treated with statins were observed during a statin intake period of 3 to 132 months; though the observed duration ranged widely, compared to other studies relatively long-term use of statins was studied. Notably, a preliminary study identi ed that a high percentage of oral symptoms are associated with statin use, and these symptoms markedly improved after suspension of the treatment 9 , raising the possibility of diverse statin-induced oral adverse effects.
Myopathy, rhabdomyolysis, diabetes, and cancers have been reported as adverse effects of statins 4,27−29 . An association between statin-induced adverse events and statin therapy is infrequent 4,27−29 . Clinical trials of pravastatin therapy for hypercholesterolemia with a 15-year follow-up reported a greater incidence of prostate cancer in these patients 1 , which indicates that adverse effects may become evident after a long time such as a decade or more. Likewise, incidence of CP related to statin use might have been underestimated because of the short periods of previous studies. Our ndings may be of importance with respect to the safety of the long-term use of statins in the development of periodontitis. Therefore, patients who are prescribed statin therapy needs to be informed of the increased risk of diseases, including CP.
The mechanism underlying the association between statin use and increased risk of CP remains unclear. Statins have cholesterol-independent or pleiotropic effects attributable to several mechanisms vital to cellular functions via the post-transcriptional modi cation of mevalonate intermediates in multiple tissues, including the periodontium 1-4, 20,21,30 . In fact, the systemic administration of statins have potential effects in the periodontium, and it has been reported that their concentration in gingival crevicular uid is 10-to 100-fold higher than in the serum, with an anti-in ammatory effect that in uences the level of IL-1β in the gingiva. As statins also possess immunomodulatory and antimicrobial properties 31 , their long-terms effects might include a shift in the microbial balance between pathogenic and nonpathogenic species in oral cavity which has over 700 microoranisms; this deteriorates periodontal homeostasis and immune response of the host 13,32 .
Interactions between the polymicrobial synergistic and dysbiotic action, host response, and modifying factors may determine the defense against CP or its progression 13 . Individuals with defective neutrophil recruitment or neutrophil adhesion de ciencies reportedly have increased susceptibility to periodontitis 33,34 . The range of drug action observed in statin therapy seems to be greater than expected and the precise predictions of adverse events are not possible until those events occur 32 .
The strengths of this study are its large, representative, nationwide population-based data and analysis that was fully adjusted for socioeconomic status, potential risk factors, and comorbidities related to CP or statin use (e.g., fasting blood glucose, total cholesterol, obesity, alcohol, smoking, and blood pressure). To the best of our knowledge, a nationwide follow-up epidemiologic study on the association between long-term statin intake and CP risk has not previously attempted. As the KNHIS-HS data encompass information from every hospital and clinic across the entire nation without exception, full medical histories could be obtained during the followup period.
There are limitations to our study. Statin users had been treated with different statins. No information pertaining to the severity of periodontitis, measurements such as probing depth and clinical attachment loss at interproximal sites that could help diagnose CP, type, dosage, and frequency of statins, family history and genetic data of related systemic diseases were available in the health insurance database; however, the possibility of missing data was not taken into consideration.
In summary, our nationwide cohort study indicates that both men and women aged over 40 years taking statins may have a slightly increased likelihood of subsequent CP onset, especially if used long term, which warrants potential cautions regarding the onset of CP as a possible adverse effect of long-term statin use.

Data Availability
Releasing of the data by the researcher is not allowed legally. All data are available from the database of National Health Insurance Sharing Service (NHISS) https://nhiss.nhis.or.kr/ NHISS allows access to all of this data for the any researcher who promises to follow the research ethics at some cost. If you want to access the data of this article, you can download it from the website after promising to follow the research ethics.

Declarations Data Availability
Releasing of the data by the researcher is not allowed legally. All data are available from the database of National Health Insurance Sharing Service (NHISS) https://nhiss.nhis.or.kr/ NHISS allows access to all of this data for the any researcher who promises to follow the research ethics at some cost. If you want to access the data of this article, you can download it from the website after promising to follow the research ethics.