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government and international health organizations web pages, even conference reports, theses, government reports and unpublished survey data (gray literature).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.