Impact of Sociodemographic, Clinical, and Oral Health Factors on Clinical Outcomes in Hospitalized COVID-19 Patients: A Case-Control Study

Abstract

This study aimed to explore the relationships between sociodemographic factors, clinical variables, and oral hygiene status in COVID-19 patients and examine their association with disease severity, mortality, and hospital discharge. The case-control study was conducted from March to October 2021 at a university hospital. The study included 112 hospitalized patients, divided into two groups: 68 COVID-19-positive and 44 COVID-19-negative patients. Oral hygiene was assessed using the Critical Patient Oral Hygiene Index (CPOHI), and clinical data such as comorbidities, ventilation type, and lung involvement were extracted from medical records. The study found that COVID-19 positive patients were younger, had greater lung involvement, and were more likely to require mechanical ventilation compared to the control group. A higher number of remaining teeth and better dentition status were associated with better clinical outcomes, including hospital discharge. Poor oral hygiene, as indicated by higher CPOHI scores, was associated with worse outcomes, including longer ICU stays, greater lung involvement. This study highlights the significant impact of oral health on the prognosis of hospitalized COVID-19 patients, underscoring the need for improved oral hygiene management in clinical settings to enhance patient outcomes. Further research is needed to explore the long-term effects of oral care on hospitalized patients.

Keywords:
Coronavirus Infections; Oral Hygiene Index; Hospitalization; Demographic Factors; Mortality

HIGHLIGHTS

Hospitalized COVID-19 patients often exhibit poor oral hygiene, which may contribute to higher mortality.

Integrating oral health care into hospital protocols could improve overall patient health outcomes.

INTRODUCTION

At the end of 2019, the COVID-19 pandemic, caused by SARS-CoV-2, a novel strain of the Coronaviridae family, emerged in China and rapidly spread worldwide within three months [¹], triggering severe acute respiratory syndrome [²-⁵]. The clinical presentation of COVID-19 varied widely, ranging from asymptomatic cases to severe disease [⁶], with increased morbidity and mortality linked to factors such as age, gender, comorbidities, hospitalization setting, type of ventilation, severity of pulmonary involvement, and length of hospital stay [⁷]. Age was a significant demographic risk factor, with individuals over 55 years more likely to require hospitalization [⁸], while male patients faced a higher risk of severe disease [⁹]. Comorbidities, including cardiovascular disease, diabetes mellitus, hypertension, chronic obstructive pulmonary disease, and obesity, further elevated the risk of mechanical ventilation under endotracheal intubation, complications, and mortality [³, ⁵]. Hospitalized patients with severe dyspnea were at greater risk of poor outcomes [¹⁰, ¹¹], and when dyspnea progressed alongside pneumonia unresponsive to non-invasive respiratory support, ICU admission and mechanical ventilation became necessary [¹²]. Chest X-rays and CT scans were critical for assessing pulmonary involvement and monitoring progression, as greater lung impairment correlated with higher complication risks [¹³].

In addition to systemic and respiratory complications, emerging evidence suggests a link between oral health and COVID-19 severity. Poor oral hygiene has been associated with an exaggerated immune response, increasing the risk of thromboembolic complications, lung damage, and mortality in affected patients [⁶, ¹⁴-¹⁶]. This underscores the importance of oral care, particularly in hospitalized patients who may have limited ability to maintain proper hygiene. To address this, the Critical Patient Oral Hygiene Indicator (CPOHI) was developed as an assessment tool to evaluate oral hygiene in such population. The CPOHI scores the presence of dental plaque/biofilm, gingivitis, tongue coating, halitosis, airway secretions or crusts, blood, and food debris. A score of one indicates satisfactory oral hygiene, two to three indicates deficient hygiene, and more than four signifies poor hygiene [¹⁷, ¹⁸].

With the COVID-19 pandemic now largely under control, understanding its impact on hospitalized patients remains a factor to consider for future healthcare preparedness. This study aimed to investigate the relationships between sociodemographic factors (age, gender), clinical variables (comorbidities, ventilation type, pulmonary involvement), and hospital parameters (hospitalization setting, total hospitalization duration) with oral hygiene status, disease severity, and clinical outcomes. Building on prior evidence linking poor oral health to worsened COVID-19 prognosis, we compared oral health characteristics, including edentulism, number of teeth, and the oral hygiene index, between COVID-19-positive and negative patients, and examined how these factors correlated with disease severity, hospital discharge, and mortality.

MATERIAL AND METHODS

Study design

This case-control study aimed to examine the association between sociodemographic, clinical, and oral health factors and the clinical outcomes of hospitalized COVID-19 patients. The main hypothesis is that patients with poorer oral hygiene would have worse clinical outcomes, including increased severity and mortality. The study was conducted from March to October 2021 at an university hospital and was approved by the Institutional Human Research Ethics Committee (Approval No. #4.483.614). Additionally, the research adhered to the STROBE reporting guidelines [¹⁹].

Sample size

The sample size was calculated considering the difference in the proportions of oral alterations between patients admitted to the hospital with a positive (observed oral alterations: 55%) or negative (observed oral alterations: 25%) diagnosis for COVID-19 before the start of the study (January to February 2021). For a balanced sample size (N2/N1=1), we obtained at least 42 patients per observation group, with α error = 5% and power (1-β)=80%, considering the proportions of oral alterations in positive and negative patients for COVID-19 [²⁰]. The sample calculation can be referenced by the published article “COVID-19 hospitalized patients and oral changes: a case-control study” [²¹].

Inclusion criteria

Patients aged 18 years and older, of both genders, who agreed to participate in the research (or whose guardians consented) by signing the Informed Consent Form, were admitted to the Medical Clinic-COVID, ICU-COVID, General Medical Clinic, and General ICU. For the case group, confirmation of COVID-19 was required through a positive RT-PCR test for SARS-CoV-2. For the control group, participants needed to provide confirmation that SARS-CoV-2 infection had been ruled out through a negative RT-PCR test [²²].

Exclusion criteria

The exclusion criteria included patients who tested positive or negative for COVID-19 via RT-PCR but lacked sufficient data for subsequent comparisons.

Data collection

All COVID-19 biosafety protocols were strictly followed during patient assessments, which were conducted by a qualified dentist responsible for delivering oral care [²³]. Hospitalized patients were selected for both groups based on stable clinical status and vital signs, ensuring safe dental evaluations. Bedside oral assessments were performed for COVID-19-positive patients in the COVID-ICU and clinical ward, as well as for COVID-19-negative patients in the non-COVID-ICU and clinical ward. A trained and calibrated examiner conducted a single-session physical examination using a clinical mirror and an exploratory probe, recording the number of teeth present and assessing oral hygiene. Oral hygiene was evaluated using the Critical Patient Oral Hygiene Index (CPOHI), which measures seven variables: biofilm, gingivitis, coating, halitosis, secretion/crust, blood, and food residue. The index classifies hygiene status on a scale from 0 to 7, where scores of 0–1 indicate satisfactory hygiene, 2–3 denote deficient hygiene, and 4–7 represent poor hygiene [¹⁸]. Additionally, sociodemographic variables (age, sex, comorbidities) and hospital/clinical data (hospitalization setting, type of ventilation, lung involvement, and length of hospital stay until the date of dental evaluation) were retrieved from electronic medical records on the same day as the oral assessment.

Statistical analysis

JAMOVI software (JAMOVI project, 2024, Version 2.5.3.0; https://www.jamovi.org/) was used for data analysis, employing descriptive and inferential methods [²⁴]. A two-tailed significance level of p ≤ .05 was considered statistically significant. The variables were categorized as continuous, ordinal, or nominal, and appropriate statistical tests were selected based on their characteristics and by checking the statistical test assumptions for validation. Student's t-test or Mann–Whitney test were applied for numerical variables, while the Chi-square test (χ²) and Fisher's exact test were used for categorical variables.

RESULTS

After excluding 54 patients due to missing data necessary for between group comparisons, the final sample comprised 112 patients, divided into two groups: 44 patients in the control group (presenting flu-like symptoms, shortness of breath, or difficulty breathing but with a negative COVID-19 test result) and 68 patients in the case group (confirmed COVID-19 positive).

Gender distribution was similar between groups (p = 0.5), and comorbidities were not significantly associated with COVID-19 status (p = 0.7). The COVID-19-positive group had a lower average age (56.5 years) compared to the control group. The need for mechanical ventilation (p = 0.003) and lung involvement greater than 50% (p < 0.001) were significantly higher in the case group. Regarding oral health, COVID-19-positive patients had a greater number of teeth (13) and were more likely to be dentate rather than edentulous (p = 0.01) compared to the control group.

When evaluating all patients (control and case groups) concerning hospital discharge, those who were discharged were significantly younger (58.1 years), more likely to use spontaneous ventilation (p < 0.001), more frequently admitted to a medical ward (p < 0.001), and had a greater number of teeth (Table 1).

Table 1.
Sociodemographic and clinical data were categorized based on COVID-19 diagnosis and clinical outcomes.

Variables	COVID-19 (n=112)		p-value	Clinical outcome (n=112)		p-value
	Positive (n=68)	Negative (n=44)		Hospital discharge (n=75)	Death (n=37)
Age in years
Mean ± SD	56.5 ± 11.5	65.5 ± 14.8	† <0.001(s)	58.1 ± 13.8	63.6 ± 12.6	† 0.044 (s)
Gender (%)
Female	25 (22)	19 (17)	**0.55 (ns)	33 (30)	11 (10)	**0.15(ns)
Male	43 (39)	25 (22)		42 (37)	26 (23)
Comorbidities (%)
Absent	11 (10)	6 (5)	**0.79(ns)	12 (11)	5 (4)	**1.00(ns)
Present	57 (51)	38 (34)		63 (56)	32 (29)
Ventilation (%)
Spontaneous	34 (30)	35 (32)	**0.003(s)	62 (55)	7 (6)	**<0.001(s)
Mechanical	34 (30)	9 (8)		13 (12)	30 (27)
Hospital setting (%)
ICU	38 (34)	17 (15)	**0.085(ns)	25 (22)	30 (27)	**<0.001(s)
Medical clinic	30 (27)	27 (24)		50 (45)	7 (6)
Lung involvement (%)
No involvement	0 (0)	2 (2)	*<0.001(s)	2 (2)	0 (0)	*0.85(ns)
Until 50%	25 (22)	2 (2)		19 (17)	8 (7)
>50%	37 (33)	4 (4)		26 (23)	15 (13)
Atypical	1 (1)	29 (26)		20 (18)	10 (9)
No information	5 (4)	7 (6)		8 (7)	4 (4)
Number of days of hospitalization until oral evaluation
Mean ± SD	11.5 ± 8.2	10.0 ± 6.7	†0.31(ns)	10.7 ± 8.2	11.6 ± 6.3	†0.56(ns)
Total days of hospitalization
Mean ± SD	23.0 ± 16.9	22.0 ± 21.1	†0.78(ns)	21.5 ± 21.5	24.9 ± 10.5	†0.35(ns)
Dentition (%)
Edentulous	10 (9)	16 (14)	**0.011(s)	16 (14)	10 (9)	**0.63(ns)
Toothed	58 (52)	28 (25)		59 (53)	27 (24)
Dentition in number of teeth
Mean ± SD	13.1 ± 9.2	8.8 ± 9.1	†0.014(s)	12.8 ± 9.7	8.9 ± 8.1	†0.032(s)
Critical patient oral hygiene index
Satisfactory	9 (8)	12 (11)	*0.13(ns)	15 (13)	6 (5)	*0.75(ns)
Deficient	40 (36)	24 (21)		41 (37)	23 (21)
Precarious	19 (17)	8 (7)		19 (17)	8 (7)

• ^†
  Unpaired Student’s t-test;
• ^‡
  Mann-Whitney test;
• ^*
  χ²;
• ^**
  Fisher’ exact test;
• ^(s)
  significant;
• ^(ns)
  non-significant / ICU intensive care unit

Comparing the case and control groups in relation to hospital discharge, COVID-19-positive patients who were discharged were significantly younger (54.3 years), more likely to use spontaneous ventilation (p = 0.011), had lung involvement greater than 50% (p < 0.001), were dentate (p = 0.003), and had a greater number of teeth (p = 0.005). In contrast, mortality among COVID-19-positive patients was higher in those who were younger (60.0 years), required mechanical ventilation (p = 0.007), and had pulmonary involvement greater than 50% (p < 0.001) (Table 2).

Table 2.
Sociodemographic and clinical data based on outcome divided by COVID-19 status.

Variables	Hospital discharge (n=75)		p-value	Death (n=37)		p-value
	COVID-19 positive (n=45)	COVID-19 negative (n=30)		COVID-19 positive (n=23)	C COVID-19 negative (n=14)
Age in years
Mean ± SD	54.3 ± 11.3	63.7 ± 15.4	†0.003(s)	60.0 ± 11.2	69.5 ± 13.0	† 0.024(s)
Gender (%)
Female	17 (23)	16 (21)	**0.13(ns)	8 (22)	3 (8)	**0.47(ns)
Male	28 (37)	14 (19)		15 (40)	11 (30)
Comorbidities (%)
Absent	7 (9)	5 (7)	**1.0(ns)	4 (11)	1 (3)	**0.63(ns)
Present	38 (51)	25 (33)		19 (51)	13 (35)
Ventilation (%)
Spontaneous	33 (44)	29 (39)	**0.011(s)	1 (3)	6 (16)	**0.007(s)
Mechanical	12 (16)	1 (1)		22 (59)	8 (22)
Hospital setting (%)
ICU	17 (23)	8 (11)	**0.45(ns)	21 (57)	9 (24)	**0.08(ns)
Medical clinic	28 (37)	22 (29)		2 (5)	5 (14)
Lung involvement (%)
No involvement	0 (0)	2 (3)	*<0.001(s)	0 (0)	0 (0)	*<0.001(s)
Until 50%	18 (24)	1 (1)		7 (19)	1 (3)
>50%	24 (32)	2 (3)		13 (35)	2 (5)
Atypical	1 (1)	19 (25)		0 (0)	10 (27)
No information	2 (3)	6 (8)		3 (8)	1 (3)
Number of days of hospitalization until oral evaluation
Mean ± SD	10.9 ± 8.7	10.4 ± 7.7	†0.77(ns)	12.8 ± 7.0	9.5 ± 4.2	†0.11(ns)
Total days of hospitalization
Mean ± SD	22.2 ± 19.2	20.4 ± 24.8	†0.72(ns)	24.6 ± 11.3	25.6 ± 9.3	†0.78(ns)
Dentition (%)
Edentulous	4 (5)	12 (16)	**0.003(s)	6 (16)	4 (11)	**1.0(ns)
Toothed	41 (55)	18 (24)		17 (46)	10 (27)
Dentition in number of teeth
Mean ± SD	15.3 ± 9.1	9.0 ± 9.6	†0.005(s)	9.0 ± 8.2	8.3 ± 8.3	†0.8(ns)
Critical patient oral hygiene index
Satisfactory	6 (8)	9 (12)	*0.13(ns)	3 (8)	3 (8)	*0.79(ns)
Deficient	25 (33)	16 (21)		15 (40)	8 (22)
Precarious	14 (19)	5 (7)		5 (13)	3(8)

• ^†
  Unpaired Student’s t-test;
• ^‡
  Mann-Whitney test;
• ^*
  X²;
• ^**
  Fisher’ exact test;
• ^(s)
  significant;
• ^(ns)
  non-significant
• ICU intensive care unit

Spontaneous ventilation (p = 0.03) and ICU admission (p = 0.03) were significantly more frequent among COVID-19 patients with poor CPOHI than in those without the disease. Patients with COVID-19 and satisfactory CPOHI showed a statistically significant association with pulmonary involvement of less than 50% and atypical pulmonary findings (p = 0.014). In contrast, COVID-19-positive patients with poor CPOHI (p < 0.001) and very poor CPOHI (p < 0.001) were significantly more likely to have pulmonary involvement exceeding 50% compared to the control group. Additionally, a higher number of teeth was strongly associated with better oral hygiene, with statistical significance observed in COVID-19 patients with both satisfactory CPOHI (p = 0.001) and deficient CPOHI (p = 0.001) (Table 3).

Table 3.
Sociodemographic and clinical data based on CPOHI divided by COVID-19 status.

Variables	CPOHI Satisfactory (n=21)		p-value	CPOHI Deficient (n=64)		p-value	CPOHI Precarius (n=27)		p-value
	COVID-19 positive (n=9)	COVID-19 negative (n=12)		COVID-19 positive (n=40)	COVID-19 negative (n=24)		COVID-19 positive (n=19)	COVID-19 negative (n=8)
Age in years
Mean ± SD	59.4±13.9	72.0±11.6	†0.035(s)	55.5±11.6	56.2±10.4	†0.009(s)	57.8±12.6	57.8±12.6	†0.72(ns)
Gender (%)
Female	5 (4)	4 (5)	**0.39(ns)	16 (16)	10 (10)	**1.0(ns)	4 (6)	5 (3)	**0.07(ns)
Male	4 (5)	8 (7)		24 (24)	14 (14)		15 (13)	3 (5)
Comorbidities (%)
Absent	0 (0)	1 (1)	**1.0(ns)	8 (7)	4 (5)	**1.0(ns)	3 (3)	1 (1)	**1.0(ns)
Present	9 (9)	11 (11)		32 (33)	20 (19)		16 (16)	7 (7)
Ventilation (%)
Spontaneous	5 (7)	11 (9)	**0.12(ns)	21 (25)	19 (15)	**0.03(s)	8 (9)	5 (4)	**0.42(ns)
Mechanical	4 (2)	1 (3)		19 (15)	5 (9)		11 (10)	3 (4)
Hospital setting (%)
ICU	3 (3)	5 (5)	**1.0(ns)	23 (19)	7 (11)	**0.039(s)	12 (12)	5 (5)	**1.0(ns)
Medical clinic	6 (6)	7 (7)		17 (21)	17 (13)		7 (7)	3 (3)
Lung involvement (%)
No involvement	0 (0)	0 (0)	*0.014(s)	0 (1)	2 (1)	*<0.001(s)	0 (0)	0 (0)	*<0.001(s)
Until 50%	5 (3)	1 (3)		13 (9)	1 (5)		7 (5)	0 (2)
>50%	4 (3)	3 (4)		22 (14)	0 (8)		11 (8)	1 (4)
Atypical	0 (2)	5 (3)		1 (12)	19 (8)		0 (3)	5 (2)
No information	0 (1)	3 (2)		4 (4)	2 (2)		1(2)	2 (1)
Number of days of hospitalization until oral evaluation
Mean ± SD	12.3±9.5	8.6±4.4	†0.251(ns)	10.1±6.9	11.0±8.2	†0.655(ns)	14.2±9.5	9.3±4.1	†0.18(ns)
Dentition in number of teeth
Mean ± SD	17.2±9.6	1.8±4.4	†0.001(s)	14.9±6.8	7.4±7.9	†0.001(s)	14.3±6.0	14.0±9.6	†0.92(ns)
Outcome (%)
Hosp. Discharge	6 (6)	9 (9)	**1.0(ns)	25 (26)	16 (15)	**0.79(ns)	14 (13)	5 (6)	**0.65(ns)
Death	3 (3)	3 (3)		15 (14)	8 (9)		5 (6)	3 (2)

• ^†
  Unpaired Student’s t-test;
• ^‡
  Mann-Whitney test;
• ^*
  χ²;
• ^**
  Fisher’ exact test;
• ^(s)
  significant;
• ^(ns)
  non-significant
• ICU intensive care unit

DISCUSSION

Several risk factors can influence the potential mortality impact of COVID-19 in adults, including older age, male gender, and pre-existing comorbidities [²⁵]. The need for mechanical ventilation in severe cases and the extent of lung involvement are also linked to poorer outcomes in hospitalized patients [¹²]. Vaccination is widely regarded as an effective measure to prevent the progression of COVID-19 and reduce mortality by inducing a protective immune response [²⁶]. However, at the time this study was conducted, patients had not yet received any doses of the COVID-19 vaccine, which may help explain some of the observed results.

In this study, no statistically significant differences in disease incidence or mortality were found between genders. This contrasts with other studies that have highlighted gender differences, particularly regarding male susceptibility. It has been suggested that elevated serum testosterone levels in men may facilitate viral entry into host cells and promote viral spread [²⁵, ²⁷]. Additionally, men are more likely to engage in lifestyle risk factors such as smoking, which can increase their vulnerability to the virus [²⁸]. Men also tend to have higher rates of comorbidities, contributing to an elevated risk of severe outcomes, including the development of a cytokine storm, a key factor in COVID-19-related mortality [²⁹]. These factors indicate that while our study did not observe significant gender-based differences in outcomes, biological and lifestyle factors likely play a role in the varying mortality rates observed in broader populations.

When all patients were assessed together, older patients were more likely to die. However, when comparing the COVID-19 and control groups, hospitalized COVID-19 patients were, on average, younger. This finding was consistent across both satisfactory and poor CPOHI. This shift in patient demographics may be attributed to the timing of the study, as the early phase of the pandemic predominantly affected older individuals, who had higher mortality rates. Over time, younger individuals increasingly made up the hospitalized patient population, leading to higher mortality rates within this group. This trend, often referred to as “pandemic youth,” reflects a broader demographic shift observed in studies examining the age profile of patients [³⁰]. Additionally, mortality risk was more strongly associated with age during earlier waves of the pandemic [³¹].

Comorbidities are closely tied to older age, as older patients typically have a higher prevalence of underlying conditions [²⁸]. Since this study focused on a younger patient population, this may explain why comorbidities did not show a significant association with COVID-19 outcomes. However, previous reviews have identified hypertension, diabetes, and cardiovascular disease as the most common comorbidities in COVID-19 patients, all of which are associated with increased disease severity [³²]. More recent reviews have also highlighted asthma, COPD, cardiovascular disease, lung cancer, and type 2 diabetes mellitus as comorbidities that worsen COVID-19 outcomes [³¹].

In this study, mechanical ventilation was associated with higher mortality, particularly among patients with COVID-19. Notably, COVID-19 patients who required mechanical ventilation had a higher mortality rate compared to those without COVID-19, who more frequently used spontaneous ventilation. While ventilatory support is essential during the acute phase of COVID-19 [¹²], prolonged mechanical ventilation can lead to lung damage and secondary infections, thereby increasing the risk of mortality [³³, ³⁴]. These findings align with previous studies that have linked mechanical ventilation to higher mortality, particularly as COVID-19 progresses to Severe Acute Respiratory Syndrome [³³, ³⁴].

The study also found a significant association between hospitalization for COVID-19 and increased mortality in patients with >50% lung involvement. Additionally, hospitalized COVID-19 patients with satisfactory oral hygiene had <50% lung involvement, while those with poor or inadequate oral hygiene had >50% lung involvement. Although RT-PCR remains the gold standard for diagnosing COVID-19, non-contrast chest CT can be a valuable tool for early assessment, especially in high-prevalence areas [³⁵, ³⁶]. CT scans typically reveal acute interstitial lung damage caused by the viral infection [³⁵, ³⁷, ³⁸, ³⁹]. The extent of lung involvement, categorized from none to severe, correlates with disease severity, with patients showing >50% involvement being more likely to require ICU admission or succumb to the disease [⁴⁰, ⁴¹]. These findings underscore the critical role of CT in assessing COVID-19 severity and support the results of this study.

Patients hospitalized with COVID-19 were more likely to be discharged if they had a greater number of remaining teeth. Additionally, a higher number of teeth was significant in COVID-19 patients with both satisfactory and poor oral hygiene, but it was not associated with poor hygiene. However, the CPOHI (Decayed, Missing, and Filled Teeth Index) did not show any significant differences between the groups. Both groups had a notably higher number of patients with poor or inadequate oral hygiene compared to those with satisfactory hygiene.

Poor oral hygiene, when combined with COVID-19 infection and its associated treatments, can contribute to negative oral health outcomes. These include opportunistic fungal infections, recurrent oral herpes simplex virus (HSV-1) infections, ageusia, xerostomia (dry mouth due to reduced salivary flow), ulcerations, and gingivitis, all of which may result from an impaired immune system [⁴²]. This study found that ICU admission in COVID-19 patients was associated with poor CPOHI. Poor oral health is prevalent among hospitalized patients and is linked to more severe symptoms of COVID-19, higher rates of ICU admission, and increased mortality. Previous studies have shown that poor dental and periodontal health, assessed using indices such as decayed, missing, and filled teeth, is associated with worse clinical outcomes [⁴³].

Furthermore, oral health assessments in ICU patients, using scores such as the modified Beck Oral Assessment Score, have emphasized the importance of oral hygiene protocols, such as tooth brushing, in reducing oral bacterial imbalances. However, these protocols did not significantly reduce healthcare-associated infections or mortality [⁴⁴]. A comprehensive assessment of sociodemographic, clinical, and oral health factors is crucial for better risk stratification of COVID-19 patients and highlights the need for a multidisciplinary approach that includes oral health care to mitigate complications. Further research is needed to fully understand the relationship between oral health and overall health outcomes in COVID-19.

This study has some limitations, including a relatively small sample size and data from a single hospital, which may affect the generalizability of the findings. The exclusion of participants due to missing data could have introduced selection bias. Its cross-sectional design prevents establishing causality between oral health and clinical outcomes, and oral hygiene was assessed only once, not accounting for changes during hospitalization. Additionally, unmeasured confounders, such as medication use and oral care timing, may have influenced the results.

CONCLUSION

This study highlights the significant impact of sociodemographic, clinical, and oral health factors on the clinical outcomes of hospitalized COVID-19 patients. Key findings indicate that younger age, greater lung involvement, and the need for mechanical ventilation are strongly associated with worse outcomes, including higher mortality. Importantly, oral health emerged as a critical factor influencing patient prognosis. Patients with better dentition status and satisfactory oral hygiene, as measured by the CPOHI, were more likely to be discharged, while those with poor oral hygiene faced longer ICU stays and greater lung involvement.

• Funding:
  This research was partially supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES) — Finance Code 001.
• Institutional Review Board Statement:
  Approved by the Institutional Ethics Committee on Human Research (# 4.483.614)
• Informed Consent Statement:
  Informed consent was obtained from all subjects involved in the study.

Acknowledgments:

I would like to thank HURCG for allowing us to serve at their establishment, as well as helping us with materials for hospital care.

Data Availability Statement:

data are available on reasonable request for corresponding author.

• Use of Generative Artificial Intelligence:
  The authors declare that no generative artificial intelligence (AI) or AI-assisted technologies were used to generate or modify the scientific content of this manuscript, including the conception of the study, data collection, data analysis, interpretation of results, or creation of original text, figures, tables or graphical abstracts, apart from routine tools for spelling, grammar checking and reference management that do not create original scholarly content.

REFERENCES

• ¹ Gralinski LE, Menachery VD. Return of the Coronavirus: 2019-nCoV. Viruses. 2020 Jan 24;12(2):135. doi: 10.3390/v12020135.
  » https://doi.org/10.3390/v12020135
• ² Dong E, Ratcliff J, Goyea TD, Katz A, Lau R, Ng TK, et al. The Johns Hopkins University Center for Systems Science and Engineering COVID-19 Dashboard: data collection process, challenges faced, and lessons learned. Lancet Infect Dis. 2022 Dec;22(12):e370-6. doi: 10.1016/S1473-3099(22)00434-0. Erratum in: Lancet Infect Dis. 2022 Nov;22(11):e310. doi: 10.1016/S1473-3099(22)00645-4.
  » https://doi.org/10.1016/S1473-3099(22)00434-0
• ³ Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020 Mar 28;395(10229):1054-62. doi: 10.1016/S0140-6736(20)30566-3. Erratum in: Lancet. 2020 Mar 28;395(10229):1038. doi: 10.1016/S0140-6736(20)30606-1. Erratum in: Lancet. 2020 Mar 28;395(10229):1038. doi: 10.1016/S0140-6736(20)30638-3.
  » https://doi.org/10.1016/S0140-6736(20)30566-3
• ⁴ Rothan HA, Byrareddy SN. The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak. J Autoimmun. 2020 May;109:102433. doi: 10.1016/j.jaut.2020.102433.
  » https://doi.org/10.1016/j.jaut.2020.102433
• ⁵ Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020 Feb 15;395(10223):497-506. doi: 10.1016/S0140-6736(20)30183-5. Erratum in: Lancet. 2020 Feb 15;395(10223):496. doi: 10.1016/S0140-6736(20)30252-X.
  » https://doi.org/10.1016/S0140-6736(20)30183-5
• ⁶ Boyapati R, Dhulipalla R, Kolaparthy LK, Bodduru R. COVID-19 and oral implications: An updated review. J Oral Maxillofac Pathol. 2021 Sep-Dec;25(3):400-3. doi: 10.4103/jomfp.jomfp_198_21.
  » https://doi.org/10.4103/jomfp.jomfp_198_21
• ⁷ Gallo Marin B, Aghagoli G, Lavine K, Yang L, Siff EJ, Chiang SS, et al. Predictors of COVID-19 severity: A literature review. Rev Med Virol. 2021 Jan;31(1):1-10. doi: 10.1002/rmv.2146.
  » https://doi.org/10.1002/rmv.2146
• ⁸ CDC COVID-19 Response Team. Severe Outcomes Among Patients with Coronavirus Disease 2019 (COVID-19) - United States, February 12-March 16, 2020. MMWR Morb Mortal Wkly Rep. 2020 Mar 27;69(12):343-6. doi: 10.15585/mmwr.mm6912e2.
  » https://doi.org/10.15585/mmwr.mm6912e2
• ⁹ Palaiodimos L, Kokkinidis DG, Li W, Karamanis D, Ognibene J, Arora S, et al. Severe obesity, increasing age and male sex are independently associated with worse in-hospital outcomes, and higher in-hospital mortality, in a cohort of patients with COVID-19 in the Bronx, New York. Metabolism. 2020 Jul;108:154262. doi: 10.1016/j.metabol.2020.154262.
  » https://doi.org/10.1016/j.metabol.2020.154262
• ¹⁰ Duan J, Wang X, Chi J, Chen H, Bai L, Hu Q, et al. Correlation between the variables collected at admission and progression to severe cases during hospitalization among patients with COVID-19 in Chongqing. J Med Virol. 2020 Nov;92(11):2616-22. doi: 10.1002/jmv.26082.
  » https://doi.org/10.1002/jmv.26082
• ¹¹ Xie J, Covassin N, Fan Z, Singh P, Gao W, Li G, et al. Association Between Hypoxemia and Mortality in Patients With COVID-19. Mayo Clin Proc. 2020 Jun;95(6):1138-47. doi: 10.1016/j.mayocp.2020.04.006.
  » https://doi.org/10.1016/j.mayocp.2020.04.006
• ¹² Cronin JN, Camporota L, Formenti F. Mechanical ventilation in COVID-19: A physiological perspective. Exp Physiol. 2022 Jul;107(7):683-93. doi: 10.1113/EP089400.
  » https://doi.org/10.1113/EP089400
• ¹³ Rubin GD, Ryerson CJ, Haramati LB, Sverzellati N, Kanne JP, Raoof S, et al. The Role of Chest Imaging in Patient Management During the COVID-19 Pandemic: A Multinational Consensus Statement From the Fleischner Society. Chest. 2020 Jul;158(1):106-16. doi: 10.1016/j.chest.2020.04.003.
  » https://doi.org/10.1016/j.chest.2020.04.003
• ¹⁴ Amar S, Han X. The impact of periodontal infection on systemic diseases. Med Sci Monit. 2003 Dec;9(12):RA291-9.
• ¹⁵ Vaninov N. In the eye of the COVID-19 cytokine storm. Nat Rev Immunol. 2020 May;20(5):277. doi: 10.1038/s41577-020-0305-6.
  » https://doi.org/10.1038/s41577-020-0305-6
• ¹⁶ Olsen I, Yamazaki K. Can oral bacteria affect the microbiome of the gut? J Oral Microbiol. 2019 Mar 18;11(1):1586422. doi: 10.1080/20002297.2019.1586422.
  » https://doi.org/10.1080/20002297.2019.1586422
• ¹⁷ Farid H, Khan M, Jamal S, Ghafoor R. Oral manifestations of Covid-19-A literature review. Rev Med Virol. 2022 Jan;32(1):e2248. doi: 10.1002/rmv.2248.
  » https://doi.org/10.1002/rmv.2248
• ¹⁸ Saldanha KFD, Costa DC da, Pinto SF, Gaetti Jardim EC. [Assessment of the oral hygiene index of the critically ill patient]. Arch Health Invest [Internet]. 2016 Jan 31;4(6). Brazil. Available from: https://www.archhealthinvestigation.com.br/ARCHI/article/view/1290
  » https://www.archhealthinvestigation.com.br/ARCHI/article/view/1290
• ¹⁹ Von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP; STROBE Initiative. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007 Oct 20;370(9596):1453-7. doi: 10.1016/S0140-6736(07)61602-X.
  » https://doi.org/10.1016/S0140-6736(07)61602-X
• ²⁰ Faul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007 May;39(2):175-91. doi: 10.3758/bf03193146.
  » https://doi.org/10.3758/bf03193146
• ²¹ Ferreira MD, López LZ, da Silva FP, Miléo FC, Bortoluzzi MC, Dos Santos FA. COVID-19 hospitalized patients and oral changes: a case-control study. Clin Oral Investig. 2023 Aug;27(8):4481-91. doi: 10.1007/s00784-023-05070-7.
  » https://doi.org/10.1007/s00784-023-05070-7
• ²² World Health Organization [Internet]. Coronavirus disease (COVID-19). 2021- [cited 2021 Feb 16]. Available at: https://www.who.int/health-topics/coronavirus#tab=tab_1
  » https://www.who.int/health-topics/coronavirus#tab=tab_1
• ²³ Cirillo N. COVID-19 outbreak: succinct advice for dentists and oral healthcare professionals. Clin Oral Investig. 2020 Jul;24(7):2529-35. doi: 10.1007/s00784-020-03323-3.
  » https://doi.org/10.1007/s00784-020-03323-3
• ²⁴ The jamovi project. jamovi (Version 2.5) [Computer Software]. 2024. Available at: https://www.jamovi.org
  » https://www.jamovi.org
• ²⁵ Zhang JJ, Dong X, Liu GH, Gao YD. Risk and Protective Factors for COVID-19 Morbidity, Severity, and Mortality. Clin Rev Allergy Immunol. 2023 Feb;64(1):90-107. doi: 10.1007/s12016-022-08921-5.
  » https://doi.org/10.1007/s12016-022-08921-5
• ²⁶ Hodgson SH, Mansatta K, Mallett G, Harris V, Emary KRW, Pollard AJ. What defines an efficacious COVID-19 vaccine? A review of the challenges assessing the clinical efficacy of vaccines against SARS-CoV-2. Lancet Infect Dis. 2021 Feb;21(2):e26-e35. doi: 10.1016/S1473-3099(20)30773-8.
  » https://doi.org/10.1016/S1473-3099(20)30773-8
• ²⁷ Papadopoulos V, Li L, Samplaski M. Why does COVID-19 kill more elderly men than women? Is there a role for testosterone? Andrology. 2021 Jan;9(1):65-72. doi: 10.1111/andr.12868.
  » https://doi.org/10.1111/andr.12868
• ²⁸ Gao YD, Ding M, Dong X, Zhang JJ, Kursat Azkur A, Azkur D, et al. Risk factors for severe and critically ill COVID-19 patients: A review. Allergy. 2021 Feb;76(2):428-55. doi: 10.1111/all.14657.
  » https://doi.org/10.1111/all.14657
• ²⁹ Pradhan A, Olsson PE. Sex differences in severity and mortality from COVID-19: are males more vulnerable? Biol Sex Differ. 2020 Sep 18;11(1):53. doi: 10.1186/s13293-020-00330-7.
  » https://doi.org/10.1186/s13293-020-00330-7
• ³⁰ Guimarães RM, Portela MC, Villela DAM, Correa Matta G, de Freitas CM. Younger Brazilians hit by COVID-19 - What are the implications? Lancet Reg Health Am. 2021 Sep;1:100014. doi: 10.1016/j.lana.2021.100014.
  » https://doi.org/10.1016/j.lana.2021.100014
• ³¹ Zsichla L, Müller V. Risk Factors of Severe COVID-19: A Review of Host, Viral and Environmental Factors. Viruses. 2023 Jan 7;15(1):175. doi: 10.3390/v15010175.
  » https://doi.org/10.3390/v15010175
• ³² Wolff D, Nee S, Hickey NS, Marschollek M. Risk factors for Covid-19 severity and fatality: a structured literature review. Infection. 2021 Feb;49(1):15-28. doi: 10.1007/s15010-020-01509-1.
  » https://doi.org/10.1007/s15010-020-01509-1
• ³³ Grasselli G, Cattaneo E, Florio G, Ippolito M, Zanella A, Cortegiani A, et al. Mechanical ventilation parameters in critically ill COVID-19 patients: a scoping review. Crit Care. 2021 Mar 20;25(1):115. doi: 10.1186/s13054-021-03536-2.
  » https://doi.org/10.1186/s13054-021-03536-2
• ³⁴ Ñamendys-Silva SA, Gutiérrez-Villaseñor A, Romero-González JP. Hospital mortality in mechanically ventilated COVID-19 patients in Mexico. Intensive Care Med. 2020 Nov;46(11):2086-8. doi: 10.1007/s00134-020-06256-3.
  » https://doi.org/10.1007/s00134-020-06256-3
• ³⁵ Pontone G, Scafuri S, Mancini ME, Agalbato C, Guglielmo M, Baggiano A, et al. Role of computed tomography in COVID-19. J Cardiovasc Comput Tomogr. 2021 Jan-Feb;15(1):27-36. doi: 10.1016/j.jcct.2020.08.013.
  » https://doi.org/10.1016/j.jcct.2020.08.013
• ³⁶ Ai T, Yang Z, Hou H, Zhan C, Chen C, Lv W, et al. Correlation of Chest CT and RT-PCR Testing for Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases. Radiology. 2020 Aug;296(2):E32-E40. doi: 10.1148/radiol.2020200642.
  » https://doi.org/10.1148/radiol.2020200642
• ³⁷ Felsenstein S, Herbert JA, McNamara PS, Hedrich CM. COVID-19: Immunology and treatment options. Clin Immunol. 2020 Jun;215:108448. doi: 10.1016/j.clim.2020.108448.
  » https://doi.org/10.1016/j.clim.2020.108448
• ³⁸ Giamarellos-Bourboulis EJ, Netea MG, Rovina N, Akinosoglou K, Antoniadou A, Antonakos N, et al. Complex Immune Dysregulation in COVID-19 Patients with Severe Respiratory Failure. Cell Host Microbe. 2020 Jun 10;27(6):992-1000.e3. doi: 10.1016/j.chom.2020.04.009.
  » https://doi.org/10.1016/j.chom.2020.04.009
• ³⁹ Qin C, Zhou L, Hu Z, Zhang S, Yang S, Tao Y, et al. Dysregulation of Immune Response in Patients With Coronavirus 2019 (COVID-19) in Wuhan, China. Clin Infect Dis. 2020 Jul 28;71(15):762-8. doi: 10.1093/cid/ciaa248.
  » https://doi.org/10.1093/cid/ciaa248
• ⁴⁰ Li K, Fang Y, Li W, Pan C, Qin P, Zhong Y, et al. CT image visual quantitative evaluation and clinical classification of coronavirus disease (COVID-19). Eur Radiol. 2020 Aug;30(8):4407-16. doi: 10.1007/s00330-020-06817-6.
  » https://doi.org/10.1007/s00330-020-06817-6
• ⁴¹ Ruch Y, Kaeuffer C, Ohana M, Labani A, Fabacher T, Bilbault P, et al. CT lung lesions as predictors of early death or ICU admission in COVID-19 patients. Clin Microbiol Infect. 2020 Oct;26(10):1417.e5-1417.e8. doi: 10.1016/j.cmi.2020.07.030.
  » https://doi.org/10.1016/j.cmi.2020.07.030
• ⁴² Dziedzic A, Wojtyczka R. The impact of coronavirus infectious disease 19 (COVID-19) on oral health. Oral Dis. 2021 Apr;27 Suppl 3(Suppl 3):703-6. doi: 10.1111/odi.13359.
  » https://doi.org/10.1111/odi.13359
• ⁴³ Costa CA, Vilela ACS, Oliveira SA, Gomes TD, Andrade AAC, Leles CR, et al. Poor oral health status and adverse COVID-19 outcomes: A preliminary study in hospitalized patients. J Periodontol. 2022 Dec;93(12):1889-1901. doi: 10.1002/JPER.21-0624.
  » https://doi.org/10.1002/JPER.21-0624
• ⁴⁴ Gregorczyk-Maga I, Pałka A, Fiema M, Kania M, Kujawska A, Maga P, et al. Impact of tooth brushing on oral bacteriota and health care-associated infections among ventilated COVID-19 patients: an intervention study. Antimicrob Resist Infect Control. 2023 Mar 8;12(1):17. doi: 10.1186/s13756-023-01218-y. Erratum in: Antimicrob Resist Infect Control. 2023 May 29;12(1):51. doi: 10.1186/s13756-023-01256-6.
  » https://doi.org/10.1186/s13756-023-01218-y

Edited by

• Editor-in-Chief:
  Paulo Vitor Farago

• Associate Editor:
  Paulo Vitor Farago

Publication Dates

• Publication in this collection
  27 July 2026
• Date of issue
  2026

History

• Received
  03 June 2025
• Accepted
  31 Dec 2025