In a previous post, I had questioned how reliable Global Burden of Disease (GBD) estimates of severe periodontitis actually are. The reason was a recent editorial by Kocher and Holtreter (2017) who had asked, “Is the prevalence of periodontitis declining or not?” In a paper by Kassebaum et al. (2014), severe periodontitis had been identified as the 6th most prevalent disease worldwide with 11.2% (743 million) cases in 2010; while in a later paper by the same authors (Kassebaum et al. 2017) an estimate of 7.4% (538 million) in 2015 was published. Case definitions had not changed but maybe the data base has grown?
Prevalence (even incidence) data by Kassebaum et al. (2014, 2017) have been widely discussed, and a questionable measure, disability-adjusted life years (DALY), criticized, as it adopts disability weights which are, in case of severe periodontitis, very low as compared to serious diseases and conditions.
I had contacted Dr. Kassebaum at the University of Washington in Seattle and received meanwhile a kind response. He provided me with a link to the GBD database. Below is displayed the age-standardized prevalence of severe periodontitis in 2016.
Denmark and Kenya lead with more than 20% age-standardized prevalence.
In a recent editorial in Quintessence’s Oral Health & Preventive Dentistry, Kocher & Holtfreter (2017) had asked, “Is the prevalence of periodontitis declining or not?” and had referred to the “landmark paper” by Kassebaum et al. (2014) in which the “global burden of severe periodontitis” was estimated at about 11%, or 743 million. The first Kassebaum paper had sparked considerable interest claiming that severe periodontitis was, in 2010, “the sixth most prevalent condition in the world.”
As with all Global Burden of Disease (GBD) reports, in the paper by Kassebaum et al. (2014) data of a large number of very heterogenous epidemiological studies was used from all over the world and metaregression done. Published studies were supplemented with hand searches of reference lists of relevant publications and textbooks, government and international health organizations web pages, even conference reports, theses, government reports and unpublished survey data (gray literature).
Based on 65 prevalence studies, but only 2 (or 3; reported numbers differ in the flow chart describing selection of studies, and text) incidence studies as well as 5 (or 6) mortality (sic!) studies, Kassebaum et al. (2014) were able to estimate prevalence patterns in 1990 and 2010 (which strangely appear to be static) and made the strong claim (based on 2 or 3 studies) that incidence of severe periodontitis peaks at about age 38 years with more than 2000 new cases per year among 100,000.
Garbage in, garbage out?
A few words on heterogeneity of data. Kassebaum et al. (2014) had “identified 3 comparable quantitative indicators” of severe periodontitis, i.e. CPITN score of 4, attachment loss of >6 mm, and pocket depth of >5 mm. Taken as a singular observation, none of these indicators, per se, would actually point to “severe periodontitis” which would be considered a much more serious disease. Extent of the disease is of importance when describing periodontal disease, something which periodontists are or should be aware of. Mixing partial and full-mouth probing in the various studies considered is another caveat (or flaw) in Kassebaum’s analysis. One might instantly think, garbage in – garbage out.