Yesterday, new NHANES 2009-2012 data on prevalence, extent and severity of periodontitis have gone online in the Journal of Periodontology. On first sight, authors confirm findings of the previous, 2009-2010, survey in that prevalence is much larger as previously reported. So, 46% of U.S. adults have periodontitis with almost 9% having severe disease (Eke et al. 2015). The previous report (Eke et al. 2012a) contained an unclear description of how attachment loss was measured concealing that a “signed” measure of recession was used to calculate clinical attachment loss as difference of probing pocket depth and recession (from Latin, recessus, retreat). In a letter to the Editor-in-Chief of the Journal of Dental Research, Professor Giannobile, I had raised more problems in the article when I wrote,
“Teaching in particular undergraduates about how probing parameters periodontal probing depth, attachment level, and recession are measured is quite an effort but usually straightforward. In order to avoid undue exaggeration of prevalence, extent and severity of periodontitis both in the population and in patients attending a common office and to be able to assess treatment outcomes, metric periodontal probing parameters have to be properly defined. I would therefore appreciate if authors could comment on the apparent redefinition of attachment loss in their paper. When analyzing the Figure in the paper by Eke et al. (2012a), what immediately hits the eye is that there seems to be higher prevalence of attachment loss at different thresholds (a) than of pocket depth at respective thresholds (b) in all age groups. Such a pattern may actually be a result of how attachment loss had erroneously been redefined, most probably due to convenience. Just as a trivial example, a 4 mm probing depth without recession may be associated with either 0, 1, 2, 3, or 4 mm attachment loss, but the NHANES oral health data management program would have “instantly calculated” 4 mm. Based on the new case definition using attachment loss in addition to probing depth, prevalence of all periodontitis in the adult population of 30 years and older in the U.S. has now been estimated to exceed 47%, after 35% found in NHANES III during 1988-1994. This much higher prevalence may be due to the redefinition of attachment loss, too. Moreover, as to Eke et al. (2012a), mild periodontitis has a rather low prevalence in all age groups while moderate periodontitis is widespread (Figure c). The picture was different in NHANES III when severe periodontitis occurred with lowest, moderate periodontitis with intermediate and mild periodontitis with highest prevalence, a pattern which, I suppose, applies to many other widespread chronic diseases. The strange new pattern might indeed be explained partly by the redefinition of attachment loss as well, ultimately leading to a different distribution of cases.” (Emphasis added.)
Subtracting recession from periodontal probing depth makes sense only when true recession (the free gingival margin is located apical to the cemento-enamel junction) gets a minus sign. This was circumstantially explained to me in an email by the authors forwarded to me by Professor Giannobile, who never published my original letter. Eke et al. (2012a) had actually concealed that a signed recession definition was used. In the new update of NHANES 2009-2012, calculation of clinical attachment is now correctly described, including the signed recession definition. Eke et al. (2015) may also have realized that there is no complex chronic disease where moderate severity is more prevalent than its mild form. It is rather perplexing to see that authors have now abandoned the differentiation between moderate and mild periodontitis which they call “other” periodontitis (other than severe). They give the following reason,
“These subgroups [mild and moderate periodontitis] are not truly ordinal [sic] as the label suggests because many ‘moderate’ cases had insufficient pocket depth to qualify as ‘mild’ and we have therefore combined them and used the label ‘other‘ periodontitis.”
Eke et al. (2015) may have understood that their case definitions were not so straightforward as actually intended. In Eke et al. (2012b), mild periodontitis was defined as two or more interproximal sites with 3 mm or more clinical attachment loss AND two or more interproximal sites with pockets of 4 mm or more (not on the same tooth) OR one site with a pocket of 5 mm or more; while moderate periodontitis was suggested for cases with two or more interproximal sites with loss of clinical attachment of 4 mm or more (not on the same tooth); OR 2 or more interproximal sites with pockets of 5 mm or more (not on the same tooth). Not only our undergraduate students at UiT have some difficulties with the application of these definitions. I wondered whether the authors had noted that in many cases interproximal attachment loss of 4 mm may be present but no deep pockets of 5 mm or more. Even then, the case would be diagnosed moderate periodontitis, not mild. Since periodontitis is characterized by increased pockets and attachment loss (and Eke et al. (2015) point to that in their update), it is not clear why the definitions for mild and moderate periodontitis include the logical operator OR for just increased pocket depth without mentioning attachment loss. Only 3 years after these case definitions had been applied for the first time in the 2009-2010 NHANES, they seem already to be obsolete. The troubling message that moderate and severe periodontitis are so much more prevalent than previously thought, has been somewhat modified since “many ‘moderate’ cases had insufficient pocket depth to qualify as ‘mild'”. Case definitions make sense only if treatment would be different, but mild “moderate” cases may easily be treated by nonsurgical therapy and do not require periodontal surgery. Anyway, 9% severe periodontitis is actually quite a proportion. Authors still stress that their case definitions do not include furcation involvement and thus prevalence still may be underestimated. The question remains why they had abandoned furcation involvement which had been assessed in the 1988-1994 NHANES III.
18 February 2015 @ 6:52 pm.
Last modified February 19, 2015.