Q&A: Oral disorders

Dr. Eduardo Bernabe shares the latest findings on the burden of oral disorders.

The following transcript has been lightly edited for clarity

What are the key findings of your research?

In 2023, the WHO published the Global Oral Health Action Plan. And with that came a series of global targets and actions for many stakeholders and actors. So, one of those targets is overarching Target B, which refers to achieving a reduction of 10% in the combined prevalence of oral conditions. So for that, we actually need data to prove that by the end of 2030, by the end of this decade, we were able to achieve that reduction.

It has been challenging to collect data for the GBD enterprise. I mean, typically, we rely heavily on primary data, and that means oral health surveys that are done by government, by countries around the world. Now, there are two key features that I would like to emphasize in Figure 1 of our manuscript. So, the first one is that, for two conditions, oral cancers and cleft palate, there is much more data compared to the other conditions, dental caries, periodontitis, and edentulism. And that is probably due to the fact that cancers and cleft are not relying on oral health surveys. They are typically collected in a routine manner, from hospital records, from administrative information. So, that gives much more data compared to the other oral conditions.

There are two key findings of our research in terms of the trends in oral diseases over the past three decades. The first key finding is that oral conditions are very common. They are the most common conditions around the world. The combined prevalence of these conditions is around 47% globally. And that means they are affecting 3.7 billion people worldwide.

Of all of the oral conditions, untreated dental caries is the most common, affecting 2.5 billion people. The second key finding is that there have been considerable inequalities, or differences, between geographical regions in the world. I mean, looking at the six WHO regions, we can see that the European region is going ahead compared to the other regions in terms of controlling the burden of oral conditions, while other regions, such as the African and the Eastern Mediterranean regions, generally experience worse outcomes compared to the other four regions.

How does studying both 'prevalent cases' and 'prevalence rate' help your understanding of the results of your research?

One of the key indicators in the Global Burden of Disease is prevalence, and that can be measured in two ways. One is the number of cases of people with the condition, with the disease we are interested in. And the other one is the proportion of people affected, the frequency of people affected.

And these are two complementary indicators. So, on one side we have how many people are affected. But numbers alone don’t tell us much, because if the population grows, or if the life expectancy or the longevity of a population increases, then there would be more cases available of the disease. And that doesn’t give us a full picture.

That is why we also tend to use the prevalence, the percentage of people affected. So, what we see in Figure 2 of our manuscript is that the red line, the trends in prevalent cases, show an increase over time, over the past three decades. Just to give you an example, if we focus on the panel in the middle of the figure for main oral conditions, there has been an increase in the number of cases of 53%.

And the largest increase has been seen in the panel for oral cancer, where there is an increase of 162% in the number of cases. Now, as I said before, this depends a lot on the population growth and increases in longevity. So, to account for those demographic changes, we use also the prevalence as a percentage.

And that is what we see in the blue lines, in the blue trends. And what you see there in oral conditions is that that thing is flat. So there hasn’t really been a change in the prevalence of these oral diseases, except for oral cancer, where we can also see an increase of around 28% in the prevalence.

What is the importance of DALYs in understanding the impact of oral conditions?

Disability-adjusted life years, or DALYs, are an important metric in the in the full study because they allow comparing different conditions and different geographies. Now, for oral conditions in particular, they are quite relevant because they capture both elements. They don’t only measure the years of life lost because of premature mortality – so, not only conditions that kill, but also conditions that cause disability.

And of all the five conditions we evaluate in GBD related to the mouth, most of them don’t actually kill. They are not lethal. So we are talking about untreated dental caries here, periodontitis, and edentulism: of these five conditions, only orofacial cleft and oral cancer will kill.

So, by bringing together the DALYs associated to disability, and the DALYs associated with premature mortality, we can get a better picture about the burden of oral conditions globally and at a regional level.

So I think, in my personal opinion, we need a combined effort in terms of prevention and handling disease, management of disease. So, in terms of prevention, I think all our efforts should be to align with current preventive strategies for non-communicable diseases, especially because they share some determinants with oral conditions, such as alcohol intake, smoking, an unhealthy diet, especially in relation to intake of free sugars.

Now, in terms of addressing the current burden, the existing burden of disease, we should be advocating for the integration of oral health care services into universal health coverage, because I believe that will provide access to many people around the world that currently don’t have access to these services, and will actually protect people from the financial risk associated with out-of-pocket payment for dental care.