How Oral Health Influences Aspiration Pneumonia Risk in Elderly Stroke Patients

A Hidden Link Between the Mouth and the Lungs

Aspiration pneumonia is one of the most serious and life-threatening complications faced by elderly stroke patients. It occurs when food particles, saliva, or bacteria from the mouth are accidentally inhaled into the lungs. While swallowing difficulties after stroke are widely recognized, the role of oral hygiene and oral function in triggering aspiration pneumonia has often received less attention.

A recent study published in the International Dental Journal sheds new light on this connection, showing that the condition of the mouth—how clean it is and how well it functions—can significantly influence both the development and recurrence of aspiration pneumonia in older stroke survivors.

Why Stroke Patients Are Especially Vulnerable

After a stroke, many elderly patients experience impaired swallowing, reduced saliva production, and weakened chewing ability. These changes make it easier for harmful oral bacteria to accumulate and enter the respiratory tract. Aspiration pneumonia is not only common in this group but also associated with longer hospital stays, higher healthcare costs, and increased mortality.

Despite growing global evidence linking oral health to respiratory infections, few studies have specifically examined how oral hygiene and oral function together affect aspiration pneumonia risk in hospitalized stroke patients. This study aimed to fill that gap.

What the Researchers Did

The research team retrospectively analyzed data from 559 elderly stroke patients (aged 65 years and older) who underwent swallowing and oral evaluations at a hospital in Japan. Patients were divided into two main groups: those who developed aspiration pneumonia and those who did not.

To understand recurrence, patients with aspiration pneumonia were further classified into those who experienced repeated episodes and those who had only a single episode. The researchers examined a range of oral hygiene factors—such as dry mouth, food residue, and membranous substances in the oral cavity—as well as oral function indicators, including chewing ability, occlusion, and food intake level.

Key Findings: Oral Hygiene and Pneumonia Onset

The study found clear differences between patients who developed aspiration pneumonia and those who did not. Poor oral hygiene—especially the presence of food residue, dry mouth, and membranous substances—was strongly associated with the initial occurrence of aspiration pneumonia. In addition, patients with poor occlusion, meaning insufficient functional teeth or ineffective dentures, faced a higher risk.

These findings suggest that when the mouth is not properly cleaned or when saliva production is reduced, bacteria can easily multiply. Once aspirated into the lungs, these bacteria may trigger pneumonia—even without obvious choking events.

What Drives Recurrence of Aspiration Pneumonia

When looking at patients who experienced repeated episodes of aspiration pneumonia, the study identified a different pattern. While oral hygiene still mattered, oral function played a more critical role in recurrence. Poor food bolus formation during chewing and lower food intake ability were strongly linked to repeated pneumonia episodes.

In short, while poor oral hygiene increases the risk of pneumonia onset, impaired oral and swallowing function appears to be the main driver of recurrence.

Why These Findings Matter

This study highlights an important clinical message: preventing aspiration pneumonia requires more than treating swallowing problems alone. Structured oral hygiene care can help reduce the initial risk, while oral function rehabilitation—such as improving chewing ability and safe food intake—may be essential to prevent recurrence.

For healthcare providers, especially those involved in stroke rehabilitation, the findings support integrating oral health assessments and dental care into routine stroke management. For patients and caregivers, the message is equally clear: maintaining a clean mouth and functional oral ability is not just about comfort—it can be life-saving.

Conclusion

The study demonstrates that oral hygiene and oral function play distinct but complementary roles in aspiration pneumonia among elderly stroke patients. Poor oral hygiene increases the likelihood of pneumonia onset, while impaired oral function contributes more strongly to recurrence. Addressing both aspects through structured oral care and rehabilitation may significantly improve outcomes for this vulnerable population.

Original Article Reference

Hombo A, Kato K, Jokaji-Ishimiya M, Kobayashi Y, Hase T, Kawashiri S.

Aspiration Pneumonia Incidence and Recurrence in Elderly Stroke Patients: Oral Hygiene and Functional Status.

International Dental Journal. 2025;75:103902.

DOI: https://doi.org/10.1016/j.identj.2025.103902