Patients in hospital Intensive Care Units — ICUs — are at increased risk for contracting pneumonia, particularly if they have weakened immune systems or are frail. There appears to be a fairly simple and inexpensive way to reduce this risk and shorten their stay in the ICU: Making sure hospitalized patients' teeth are brushed daily.

Patients in intensive care can contract pneumonia when bacteria in the mouth enter a patient’s airways and infect their lungs. This is especially a risk if the person is on a ventilator.

If patients' teeth were brushed every day, investigators from Brigham and Women’s Hospital reasoned, it would reduce the amount of infectious bacteria in the mouth, potentially lowering the risk of hospital-acquired pneumonia from occurring. This is what their subsequent study found.

When patients' teeth were brushed daily, there was a significantly lower risk for hospital-acquired pneumonia and ICU mortality, fewer days of mechanical ventilation and shorter stays in the ICU.

The researchers using a variety of databases to collect and analyze the results of 15 randomized clinical trials that included more than 2,700 patients. The trials compared the effect of regular toothbrushing versus oral care without toothbrushing on the occurrence of hospital-acquired pneumonia as well as other outcomes.

Their meta-analysis revealed that daily brushing was linked to a significantly lower risk for hospital-acquired pneumonia and ICU mortality — as well as fewer days of mechanical ventilation and a shorter stay in the ICU.

“It’s rare in the world of hospital preventative medicine to find something like this that is both effective and cheap. Instead of a new device or drug, our study indicates that something as simple as brushing teeth can make a big difference,” corresponding author Michael Klompas, a hospital epidemiologist and an infectious disease physician in the Department of Medicine at BWH and Professor of Population Medicine at Harvard Pilgrim Health Care Institute, said. “If a patient cannot perform the task themselves, we recommend a member of the patient’s care team assist.”

Most of the studies in the review explored the effect of daily teeth-cleaning in adults in the ICU; only two of the 15 studies in the meta-analysis evaluated the impact of toothbrushing in non-ventilated patients. In order to know if the protective effects of toothbrushing extend to hospitalized patients in general, studies focusing on non-ventilated and other non-ICU patients are needed.

The study is published in JAMA Internal Medicine.