Can a toothbrush a day keep the doctor away?

A new study on brushing teeth in the hospital reveals some surprising findings.

Although it’s the place we should be when we’re very sick, the hospital is nevertheless a dangerous place. For starters, simply having an illness that requires hospitalization in the first place puts patients at increased risk for new problems. Then, there’s risks associated with the various treatments we give patients—risks we believe are outweighed by the benefits of such treatments, but risks nonetheless. Then there’s risks of simply being in the hospital, away from routines, in an uncomfortable bed, being awoken for vital signs and blood draws.

It’s no wonder, then, that patients who come into the hospital with one problem frequently develop new, “hospital acquired” conditions. Some of these are benign, but annoying; constipation plagues hospital units around the world. Others are more serious and even life threatening, like blood clots or pneumonias.

But as a new study highlights, there’s one simple intervention that can reduce the risk of pneumonia for hospitalized patients—so simple, a toddler could do it: brushing their teeth.

What is pneumonia, anyways?

Because the lungs are filled with air, they usually appear black on an x-ray. Pneumonia can fill up the air spaces in the lungs, making them appear white, as we can see on the left side of this stock image of a (horizontally flipped) x-ray.

Pneumonia is one of the most common causes of hospitalization and death in the U.S. and across the world. It’s a serious illness that is the result not only of a bacteria or virus infecting the lung, but the inflammatory response that the infection triggers. This can render large portions of the lung unusable for the purposes of adding oxygen to and removing carbon dioxide from the bloodstream—essential functions for life.

To cause pneumonia, bacteria need to make their way into the lungs; the main way this happens is that bacteria work their way down from the mouth with other liquids that enter the airway in an event called “aspiration.” We’re all aspirating in tiny amounts all the time, and occasionally we aspirate in larger amounts (think of that overly-aggressive sip of water you choked on that made everyone ask if you were OK). Our airways have mechanisms to clear out things that shouldn’t be down there, but under the right conditions, once deep in the lung, certain bacteria can cause pneumonia.

For patients who are in the ICU on ventilators, one way we try to prevent pneumonias is by washing their mouths out with a disinfectant called chlorhexadine. Because these patients have a breathing tube going down their throat and many of them are unconscious, the usual mechanisms that prevent bacteria-containing liquid from entering their lungs aren’t working. The idea is that if you kill the bacteria in their mouth, any saliva that does end up down in the lungs won’t have as much bacteria in it. Studies on chlorhexidine for oral care for patients on ventilators, however, are mixed when it comes to their ability to reduce pneumonia and save lives.

Of course, the rest of us reduce the burden of bacteria in our mouths using a toothbrush, a centuries-old tool that, along with toothpaste, helps remove bacteria and debris those bacteria feed on. And while the reason we do this every day is to benefit our teeth and gums, it does make you wonder: can toothbrushing help prevent pneumonia in the hospital?

The data on toothbrushing

Photo by Diana Polekhina on Unsplash

A new meta-analysis study by Harvard researchers Selina Ehrenzeller and Michael Klompas combined data from 15 different randomized controlled trials from around the world on toothbrushing to prevent hospital acquired pneumonia. They combined these studies to make one large study that included 2,786 patients randomized to a toothbrushing intervention versus control. (The control arms of these studies varied slightly, though most commonly they were comparing chlorhexidine + toothbrushing to the use of chlorhexidine alone).

They found that across these studies, toothbrushing cut down the risk of pneumonia by about one third, both for regular hospitalized patients and for patients on ventilators (a patient who can’t do it themselves would have their teeth brushed for them). The results were similar whether patients brushed their teeth 2, 3, or 4 times a day.

For patients in the ICU, the toothbrushing was associated with a 19% reduced risk of death in the ICU (studies of other patients did not include data on mortality). These ICU patients who had their teeth brushed also tended to spend less time on the mechanical ventilator and less time in the ICU than those who didn’t get their teeth brushed.

What does this mean for hospital care?

While this study is a departure from the natural experiments we typically focus on, it does demonstrate that a simple, everyday activity can have a real impact on patients. It also highlights how disruptive hospital care can be—toothbrushing is a part of everyday life for most patients, but it can easily be dismissed as unimportant when patients are feeling unwell (or unconscious as many are in the ICU).

We should also touch on the advantage of the meta-analysis research strategy of combining smaller randomized trials into one big one: it preserves the benefits of randomization from each trial. At the same time, it provides more clarity and confidence in the estimate of the effect size by including more patients. In this case, the effect appears pretty sizable, and it comes at very little cost—we have toothbrushes and toothpaste for patients in the hospital already, we just don’t always do it.

For hospital wards and ICUs that were unsure of the benefits of oral care and toothbrushing, we hope this study will help ensure it doesn’t get forgotten as a part of daily patient care. Remembering, of course, is easier said than done, which is why it’s important to make toothbrushing a part of daily protocols and routines in both the busy hospital environment as well as the chaotic environment of a household with two toddlers—though the Worsham family gets some assistance from Daniel Tiger, of course: