Risk of pneumonia and mortality after routine dental scaling in patients with moderate-to-severe cerebral palsy: A nationwide cohort study

Abstract

Background/purpose

Pulmonary infection is a major cause of hospitalization and death in individuals with cerebral palsy. The impact of routine dental scaling, a standard procedure for removing oral biofilm, on the risk of pneumonia and mortality in individuals with cerebral palsy is unknown. This study aimed to investigate the association between routine dental scaling and the risk of pneumonia and mortality in individuals with moderate-to-severe cerebral palsy.

Materials and methods

This nationwide, population-based cohort study used data derived from Taiwan’s National Health Insurance Research Database between 2009 and 2019. 12,853 individuals with moderate-to-severe cerebral palsy were identified. Individuals who received routine dental scaling for at least three consecutive years were compared to those without dental scaling. Propensity-score matching was applied to balance baseline characteristics. Multivariable Cox proportional hazards models and Fine–Gray competing-risks survival analyses were employed to estimate the hazard ratios (HRs) and 95 % confidence intervals (CIs) of pneumonia, pneumonia-related mortality, and all-cause mortality during 5-year follow-up period.

Results

Among 2,440 matched pairs, routine dental scaling was significantly associated with reduced risks of pneumonia (HR: 0.41, 95 % CI: 0.28–0.58), pneumonia-related mortality (HR: 0.23, 95 % CI: 0.13–0.41), and all-cause mortality (HR: 0.24, 95 % CI: 0.19–0.32). These findings remained consistent across various subgroup and sensitivity analyses.

Conclusion

This 11-year nationwide cohort study provides real-world evidence that routine dental scaling is associated with a substantially reduced risk of pneumonia and mortality in individuals with moderate-to-severe cerebral palsy. These findings highlight the importance of oral healthcare in preventing severe health outcomes in this vulnerable population.

Introduction

Cerebral palsy (CP) is a lifelong neurodevelopmental disorder resulting from injury to the developing brain. It encompasses a diverse spectrum of motor, sensory, cognitive, communicative, and behavioral impairments. Life expectancy among individuals with CP who have moderate to severe impairments is often shorter than the general population. 1–3 This vulnerable population commonly experiences dysphagia, aspiration and impaired airway clearance, which increase susceptibility to respiratory infections.4,5 Respiratory diseases, particularly pneumonia, constitute the primary cause of mortality, accounting for approximately 53 %–74 % of deaths in CP reported in population-based studies.2,3,6 In addition, pulmonary disorders frequently lead to recurrent hospital admissions and impose a considerable healthcare burden in people with CP.7–9

Previous studies have identified potential respiratory pathogens on tooth surfaces and dentures.10,11 Aspiration of microorganisms from the oral cavity may elevate the risk of pneumonia, particularly in patients with dysphagia or immunodeficiency. Clinical trials have shown that oral healthcare measures, such as mechanical tooth cleaning and the application of chemical disinfectants, can significantly reduce the occurrence of nosocomial pneumonia,12 ventilator-related pneumonia,13,14 and aspiration pneumonia among nursing home residents.15,16

Individuals with moderate-to-severe CP commonly exhibit impaired chewing function due to poor perioral muscle coordination, which can lead to food residue retention. Upper-limb motor limitations frequently necessitate caregiver-assisted oral hygiene; however, effective plaque removal remains challenging because of abnormal perioral muscle tone and exaggerated biting or gag reflexes. Consequently, maintaining adequate oral hygiene in this population is difficult. Previous studies have reported poorer oral hygiene indices and a higher prevalence of dental caries in the primary dentition among children with CP compared with the general population.17–19 Microorganisms released from dental plaque and calculus can be aspirated into the lower respiratory tract, leading to pulmonary infection. In addition, oral bacteria may produce hydrolytic enzymes or proinflammatory cytokines that alter respiratory epithelial surfaces, thereby facilitating the adhesion and colonization by respiratory pathogens.20 Professional dental scaling has been shown to significantly reduce the oral microbial load, and routine performance of this procedure helps maintain low levels of oral microorganisms, and potentially mitigate aspiration-related pneumonia risk in this vulnerable population.21

Although individuals with moderate-to-severe CP are known to have a markedly increased risk of developing pneumonia,4,5 limited studies have investigated the impact of oral healthcare on the risk of pneumonia in individuals with CP or other neurologic impairment.22,23 In particular, the effect of routine dental scaling on pneumonia and mortality among individuals with moderate-to-severe CP is unknown. We hypothesized that routine dental scaling would reduce the 5-year risks of pneumonia and mortality in this population. To address this gap, we conducted a nationwide, population-based cohort study using medical claims data in Taiwan to investigate the associations between routine dental scaling and the risk of pneumonia, pneumonia-related mortality, and all-cause mortality in individuals with moderate-to-severe CP.

Materials and methods

Data sources

Data on individuals with CP were obtained from the Registry for Catastrophic Illness Patients, a subcomponent of the National Health Insurance Research Database (NHIRD) in Taiwan. The available data of the NHIRD include sex, age, diagnoses, examinations, and prescriptions collected from outpatient, emergency, and inpatient services. The accuracy and validity of this database have been verified in previous studies.24,25 Mortality data, including pneumonia-related and all-cause deaths, were retrieved from the National Death Registry database. All datasets were encrypted and de-identified, and data analyses were conducted in secure onsite facilities in compliance with data privacy regulations.

Study design, population and outcomes

This retrospective cohort study identified all individuals with CP registered between 2009 and 2019 in the Registry for Catastrophic Illness Patients, based on the diagnostic codes from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM 343.x) or Tenth Revision (ICD-10-CM G80.x). According to Taiwan’s National Health Insurance (NHI) Administration, only CP individuals with moderate-to-severe disability are eligible for issuing a catastrophic illness certificate, which provides exemption from copayments and includes dental scaling benefits every three months.

Individuals who received dental scaling at least once annually for three consecutive years were classified as the exposed group, representing those receiving routine dental scaling. Dental scaling procedures were obtained via outpatient claims using the following codes: full-mouth scaling (91004C and 91104C), localized scaling (91003C and 91103C), and tooth prophylaxis (91014C and 91114C) (Supplementary Table 1). The index date was defined as the date of the first dental scaling in the third consecutive year.

The non-exposed group comprised individuals who did not receive any dental scaling procedure during the observation period. To minimize the potential confounding, a 1:1 ratio propensity score matching (PSM) was performed between two groups, accounting for the following covariates: (1) sociodemographic characteristics, such as sex, age, level of residence urbanization, low-income households, and healthcare facilities; (2) Charlson Comorbidity Index (CCI) score, previous hospital admission within one year, and comorbid conditions previously linked to pneumonia risk in CP (including dysphagia with tube feeding, epilepsy, gastro-esophageal reflux disease, asthma, pressure ulcer, and scoliosis).26 Relevant ICD-9-CM and ICD-10-CM codes of the above covariates are provided in Supplementary Table 1. To ensure identification of new-onset pneumonia, we excluded individuals hospitalized for pneumonia within one year prior to the index date.

The primary outcome was hospitalization for pneumonia, defined using primary diagnosis codes (ICD-9-CM: 480–486, 507.0, 507.8; ICD-10-CM: J12–J18, J69.0, J69.8). The secondary outcomes were pneumonia-related mortality and all-cause mortality, identified by the National Death Registry (Supplementary Table 1).

Statistical analysis

Baseline characteristics between the exposed and non-exposed groups were compared using the absolute standardized mean difference (ASMD). Generally, ASMD value less than 0.1 denotes a negligible difference and serves as a measure of matching degree.

To evaluate the association between routine dental scaling and mortality outcomes, we utilized multivariable Cox proportional hazards regression to estimate adjusted hazard ratios (HRs) and 95 % confidence intervals (CIs) for both pneumonia-related and all-cause mortality. When examining the impact of routine dental scaling on pneumonia, Fine–Gray proportional hazards models were applied while accounting for death as a competing event. We estimated the cumulative incidences for pneumonia, pneumonia-related and all-cause mortalities; and the log-rank test was applied to compare the difference in cumulative incidence between two groups. The duration of follow-up was 5 years. Study end points were defined as either the occurrence of pneumonia, 5-year follow-up, death or withdrawal from the NHI Program whichever came first.

Subgroup analyses were conducted according to sex, age, and CCI score. To enhance our findings, we conducted various sensitivity analyses using different follow-up duration and alternative definition criteria for primary outcome, respectively.

All analyses were performed using Statistical Analysis Software version 9.4 (SAS Institute Inc., Cary, NC, USA). A two-sided P value < 0.05 was considered statistically significant.

Ethics statement

This study is a retrospective observational study. All procedures were conducted in accordance with the principles outlined in the Declaration of Helsinki and the Declaration of Taipei on ethical considerations regarding health databases, issued by the World Medical Association. The study protocol was reviewed and approved by the Institutional Review Board of the Chang Gung Medical Foundation (IRB No: 202300800B0C601). The usage right of NHIRD and Death Registry were approved by the Health and Welfare Data Science Center, Ministry of Health and Welfare of Taiwan.

Results

A total of 12,853 individuals with moderate-to-severe CP between 2009 and 2019 were identified in the study. Among them, 5,500 individuals (42.8 %) met the criteria for routine dental scaling and were classified into the exposed group. After performing 1:1 ratio PSM, 2,440 matched pairs were obtained. The flow chart of individual selection process is shown in Fig. 1. Table 1 shows the baseline characteristics and related comorbidities. The median age of CP individuals at the index date was 21 years (interquartile range, 15–30 years). After matching, all ASMD values were less than 0.1, indicating no major imbalances at baseline.

Figure 1.

The flow chart of individual selection process.

Table 1.

Baseline characteristics of the study cohort before and after propensity score matching.

Characteristic	Before propensity score matching			After propensity score matching
	Routine dental scaling	No dental scaling	ASMD	Routine dental scaling	No dental scaling	ASMD
	(n = 3430)	(n = 2656)		(n = 2440)	(n = 2440)
	n (%)	n (%)		n (%)	n (%)
Sex			0.017			0.008
Male	1991 (58.1)	1564 (58.9)		1447 (59.3)	1437 (58.9)
Female	1439 (42)	1092 (41.1)		993 (40.7)	1003 (41.1)
Age at index date, median (Q1-Q3)	20 (14–29)	22 (15–30)	0.081	21 (15–30)	21 (15–30)	0.007
<20 years	1590 (46.4)	1118 (42.1)	0.084	1090 (44.7)	1059 (43.4)	0.026
≥20 years	1840 (53.6)	1538 (57.9)		1350 (55.3)	1381 (56.6)
Charlson Comorbidity Index			0.055			0.035
0	3051 (89)	2407 (90.6)		2201 (90.2)	2226 (91.2)
≥1	379 (11.1)	249 (9.4)		239 (9.8)	214 (8.8)
Urbanization level			0.267			0.000
Urban	1957 (57.1)	1167 (43.9)		1122 (46)	1131 (46.4)
Suburban	1197 (34.9)	1156 (43.5)		1056 (43.3)	1049 (43)
Rural	276 (8.1)	333 (12.5)		262 (10.7)	260 (10.7)
Low-income household	346 (10.1)	255 (9.6)	0.016	225 (9.2)	231 (9.5)	0.008
Healthcare facility			0.084			0.053
Medical center	1067 (31.1)	865 (32.6)		783 (32.1)	793 (32.5)
Regional hospital	1109 (32.3)	789 (29.7)		765 (31.4)	754 (30.9)
District hospital	538 (15.7)	381 (14.3)		347 (14.2)	356 (14.6)
Local clinic	716 (20.9)	621 (23.4)		545 (22.3)	537 (22)
Comorbidity Dysphagia with tube feeding	50 (1.5)	134 (5.1)	0.203	50 (2.1)	51 (2.1)	0.003
Epilepsy	1089 (31.8)	784 (29.5)	0.048	717 (29.4)	712 (29.2)	0.005
GERD	65 (1.9)	43 (1.6)	0.021	42 (1.7)	34 (1.4)	0.026
Asthma	91 (2.7)	59 (2.2)	0.028	52 (2.1)	53 (2.2)	0.003
Pressure ulcer	14 (0.4)	18 (0.7)	0.037	13 (0.5)	11 (0.5)	0.012
Scoliosis	96 (2.8)	33 (1.2)	0.111	33 (1.4)	30 (1.2)	0.011
Hospital admission within 1 year	430 (12.5)	303 (11.4)	0.035	278 (11.4)	265 (10.9)	0.017

Note: ASMD, absolute standardized mean difference; GERD, gastro-esophageal reflux disease.

Fig. 2 presents the risk of pneumonia over a 5-year follow-up period between two groups. Individuals who received routine dental scaling had a significantly lower risk of pneumonia compared to their counterpart (HR: 0.41, 95 % CI: 0.28–0.58). Fig. 3 illustrates the cumulative incidence for pneumonia between subjects in two groups, showing a significantly lower cumulative incidence of pneumonia in those with routine dental scaling than their counterpart (P < 0.001).

Figure 2.

Association between routine dental scaling and pneumonia, pneumonia-related mortality, and all-cause mortality during 5-year follow-up.

Note: HR, hazard ratio; CI, confidence interval.

^a adjusted for sex, age, urbanization level, low-income households, healthcare facilities, risk conditions, Charlson Comorbidity Index and hospital admission within 1 year.

^b Shown as a subdistribution hazard ratio derived from a competing-risks survival regression, with all-cause mortality considered as a competing event.

*P value < 0.05.

Figure 3.

Cumulative incidence function of pneumonia by routine dental scaling status, accounting for the competing risk of death (Fine–Gray model).

We also assessed the impact of routine dental scaling on mortality related outcomes and found significantly lower risks of both pneumonia-related mortality (HR: 0.23, 95 % CI: 0.13–0.41) and all-cause mortality (HR: 0.24, 95 % CI: 0.19–0.32) in the routine dental scaling group (Fig. 2). Kaplan–Meier curves demonstrated significantly lower cumulative incidence of both pneumonia-related and all-cause mortalities in the routine dental scaling group (Fig. 4; P < 0.001 for both outcomes).

Figure 4.

Kaplan–Meier plot for mortality outcomes in the routine dental scaling group and no dental scaling group. (A) Pneumonia- related mortality; (B) All-cause mortality.

The results from subgroup analyses stratified by sex, age, and CCI score showed consistent inverse associations between routine dental scaling and pneumonia risk across most subgroups except for the subgroup with CCI ≥1, where the result was not statistically significant, likely due to limited sample size (Table 2). Similar inverse associations were found for pneumonia-related mortality and all-cause mortality across all subgroups (Table 2).

Table 2.

Subgroup analyses of the association between routine dental scaling and relative outcomes.

	Pneumoniab		Pneumonia-related mortality		All-cause mortality
	HR (95 % CI)a	Interaction term (P value)	HR (95 % CI)a	Interaction term (P value)	HR (95 % CI)a	Interaction term (P value)
Sex		0.953		0.723		0.429
Male	0.38 (0.23–0.64)*		0.25 (0.12–0.53)*		0.26 (0.18–0.37)*
Female	0.40 (0.24–0.68)*		0.20 (0.07–0.52)*		0.21 (0.14–0.33)*
Age		0.916		0.081		0.067
<20 years	0.39 (0.23–0.68)*		0.35 (0.16–0.75)*		0.24 (0.16–0.36)*
≥20 years	0.41 (0.25–0.66)*		0.11 (0.04–0.30)*		0.22 (0.15–0.32)*
CCI
0	0.38 (0.25–0.57)*	0.524	0.24 (0.13–0.46)*	0.629	0.24 (0.18–0.32)*	0.800
≥1	0.43 (0.18–1.02)		0.06 (0.01–0.49)*		0.19 (0.10–0.38)*

Note: HR, hazard ratio; CI, confidence interval; CCI, Charlson Comorbidity Index.

^aAdjusted for sex, age, urbanization level, low-income households, healthcare facilities, risk conditions, CCI and hospital admission within 1 year.

^bShown as a subdistribution HR derived from a competing-risks survival regression, with all-cause mortality considered as a competing event.

^*Statistical significance (P value < 0.05).

To assess the robustness of our findings, we conducted two sensitivity analyses. First, we extended the follow-up period to the entire study duration, and observed similar reduced risk of pneumonia (HR: 0.37, 95 % CI: 0.27–0.52), pneumonia-related mortality (HR: 0.28, 95 % CI: 0.18–0.43) and all-cause mortality (HR: 0.28, 95 % CI: 0.22–0.34) in the routine dental scaling group (Supplementary Figure 1). When redefining the primary outcome as “new-onset pneumonia identified from any diagnosis of hospitalization”, the association remained significant, with a reduced risk in the routine dental scaling group (HR: 0.31, 95 % CI: 0.22–0.43; Supplementary Figure 2).

Discussion

In this nationwide population-based cohort study of 12,853 individuals with moderate-to-severe CP, including 2,440 matched pairs, routine dental scaling was associated with a 59 % reduced risk of pneumonia. Furthermore, routine dental scaling was also linked to a 77 % reduced risk of pneumonia-related mortality and a 76 % reduced risk of all-cause mortality, respectively. The consistent associations remained across various subgroup and sensitivity analyses, supporting the robustness of our findings. This study reveals compelling real-world evidence that routine dental scaling may significantly reduce the risks of pneumonia and mortality, in this vulnerable population.

Our findings highlight several important clinical implications. This study suggests that professional oral healthcare, specifically routine dental scaling, provides a feasible and effective strategy to reduce the risk of pneumonia, and potentially further reduce pneumonia-related mortality in this vulnerable group. Additionally, routine dental scaling, which helps to maintain good oral health and prevent infections, may also contribute to a reduced risk of all-cause mortality. Based on these findings, we recommend the implementation of routine dental scaling as part of standard care in individuals with CP.

Although an elevated risk of pneumonia in individuals with CP have been well documented, respiratory interventions such as gastrostomy tube placement and chest physiotherapy have shown limited evidence of effectiveness in previous studies.27,28 While earlier studies have suggested that the oral cavity may serve as a reservoir for pneumonia-related pathogens,10,11,29 epidemiological evidence linking oral health interventions to pneumonia prevention in the CP population remains limited. One US retrospective cohort study found that dental care within 180 days of pneumonia-related hospitalization was associated with a lower risk of subsequent pneumonia-related readmissions in children with neurologic impairment, including CP.22 Another registry-based cohort study reported an 11 % reduced risk of pneumonia among CP patients who received two or more dental visits within 180 days.23 However, these two studies examined irregular dental visits without specifying the types of dental procedures. In contrast, our study focused specifically on routine dental scaling, a standard procedure aimed at removing oral biofilm, and provided real-world evidence that routine dental scaling is associated with a significantly reduced risk of pneumonia in individuals with moderate-to-severe CP.

Previous investigations have demonstrated that professional oral biofilm removal procedures significantly decreased pneumonia occurrence among individuals with dysphagia or compromised immune function.13–16 These procedures likely reduce the oral microbial load, consequently attenuating the aspiration of saliva-borne oral bacteria into the lower respiratory tract which can lead to pneumonia. In line with these previous findings, our study demonstrates that routine dental scaling may reduce the risk of pneumonia in individuals with moderate-to-severe CP.

Beyond respiratory outcomes, routine dental scaling was also associated with reduced all-cause mortality in this vulnerable population. Respiratory diseases, mainly pneumonia, account for the majority of deaths in individuals with CP, followed by epilepsy, accidents, cardiovascular diseases, and other infections.2,3 The observed reduction in pneumonia likely contributes substantially to the observed mortality benefit. Furthermore, poor oral hygiene in individuals with CP increase the risk of dental caries and periodontal inflammation, which could plausibly contribute to systemic infections, such as sepsis, particularly in individuals with compromised immune function. Evidence from the general population has linked periodontal infection to increased risks of cardiovascular diseases,30,31 and dental scaling has been associated with reduced cardiovascular events.32–34 These findings suggest that routine dental scaling may confer systemic health effects beyond respiratory outcomes; further research is warranted to elucidate its potential impact on non-respiratory health outcomes in individuals with CP.

Managing the oral health of individuals with moderate-to-severe CP presents substantial challenges for both caregivers and dental professionals. Behavior difficulties, motor impairments and medical comorbidities create significant barriers to accessing dental care, and dental scaling is often difficult to perform because patients are prone to choking and exhibit involuntary movements. These challenges underscore the importance of integrating professional oral healthcare into comprehensive care models for individuals with CP. A multidisciplinary approach involving dentists, dental hygienists, and other healthcare professionals is essential to ensure safe and effective oral care. In Taiwan, the NHI Program provides dental scaling every three months for individuals with disabilities, offering an opportunity to promote preventive oral healthcare in individuals with CP. Public health policies should continue to improve accessibility to dental services for people with disabilities and enhance awareness among patients and caregivers of the potential systemic health benefits of routine professional dental care.

The strengths of this study are to employ PSM and include incident pneumonia in individuals with moderate-to- severe CP to minimize potential confounding at baseline sociodemographic characteristics, comorbidities, and previous pneumonia episodes; and the large sample size gave us sufficient statistical power to address the current research gap in this under-studied population.

Nevertheless, several limitations should be acknowledged. First, information on Gross Motor Function Classification System (GMFCS) levels, a known risk factor of pneumonia in CP, was not available in the NHIRD. However, this study included only individuals with moderate-to-severe disabilities identified from the Taiwan’s Registry for Catastrophic Illness, most of these individuals are likely belonged to higher GMFCS levels. Second, individual-level data on oral hygiene behaviors were also unavailable, raising the possibility of residual confounding. Previous studies have reported poor oral hygiene in individuals with CP, largely attributable to impaired motor function and difficulties with caregiver-assisted oral care,17–19 and caregiver education alone may not substantially reduce plaque accumulation.35,36 Nevertheless, we believe the magnitude of this confounding is likely limited, as professional dental scaling provides mechanical plaque and calculus removal that cannot be achieved through toothbrushing alone. Third, although the diagnosis of pneumonia based on diagnostic code may raise concerns, we defined pneumonia based on the primary diagnosis from inpatient medical claims data, which likely improved the outcome validity. Nonetheless, the findings reported in this study should be interpreted with caution due to the observational nature of the data.

In conclusion, this 11-year nationwide population-based cohort study demonstrates that routine dental scaling is associated with 59 %, 77 %, and 76 % reduction in the risks of pneumonia, pneumonia-related mortality, and all-cause mortality in individuals with moderate-to-severe CP. Given the limited effectiveness of current respiratory interventions in this population, our findings underscore the potential benefits of routine dental scaling in preventing pneumonia and mortality and support the importance of its implementation as standard dental care for individuals with moderate-to-severe CP.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.jds.2025.07.3550.

Funding Statement

This work was supported by grants from National Science and Technology Council of Taiwan (112-2314-B-182-030-MY3, 114-2321-B-182-005, and 111-2314-B-400-040-MY3), Chang Gung Medical Foundation (CMRPG3F1711-3, CMRPG3J0121-3, CMRPG3K1371-2, CMPRG3M1381-3, and CMRPG3N0371-3), and National Health Research Institutes, Taiwan (PH-114-PP-08).