Linda Cheng DDS, FAGD, ABGD
Emerging evidence supports an association between metabolic syndrome (MetS) and periodontal disease (PD).
In patients with periodontal disease, is there a bilateral association with MetS compared to those without periodontal disease?
Two independent reviewers searched, with no language restrictions, for case-control, cross-sectional, cohort studies and population surveys in humans with measures of MetS and PD and/or controls in more than four databases and through the references of retrieved studies and published literature, peer-reviewed studies, reports, book chapters, conference abstracts, and narrative reviews. Personal communication with journal editors for existence of grey literature up to May 30, 2012 yielded no additional results. The authors excluded papers for the following reasons: not reporting outcome of interest, duplicate reports, reviews, and focus on medical subgroups. Kappa scores were 85 percent at the initial screening of titles and 100 percent at the final screening of full-text articles. Authors resolved disagreements by consensus.
The authors identified one longitudinal, four case-control, and 15 cross-sectional studies from 12 different countries. The authors noted 6.3 percent to 78.8 percent of the subjects had PD while 5 percent to 78.9 percent had MetS. Each of the studies defined PD and MetS differently, so the authors used existing definitions to set diagnostic criteria for what constituted a “secure” or “insecure/unclear” diagnosis of PD and MetS in this SR. Meta-analysis of cross-sectional and case-control studies shows that MetS is positively associated with PD (odds ratio (OR) = 1.71, 95 percent CI: 1.42 to 2.03, n=36,337) with the association even greater in subjects with “secure” diagnoses of PD (OR = 2.10, 95 percent CI: 1.28 to 3.44, n=16,405). Nearly 40 percent of the total study participants with MetS had PD.
This SR finds that participants with MetS were nearly two times more likely to have PD. Larger longitudinal studies are needed to confirm this association and explore the possibility of preventing or treating PD with an effective management of MetS or vice versa.
Source of Funding:
Periodontal Research Fund of the University College London
Importance and Context:
MetS is a common medical condition that is an ever increasing, considerable public health concern, affecting 17 percent to 32 percent of the general population . Individuals with MetS suffer from obesity, insulin resistance, hypertension, and/or hypercholesterolemia. Researchers suspect PD is associated with MetS, with complications of both conditions increasing with age and benefiting from early intervention and referrals for treatment.
Strengths and Weaknesses of the Systematic Review:
The authors established a detailed a priori protocol in this thorough and well-conducted SR to avoid introducing bias on the direction of causality between PD and MetS. They reported the results following the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guideline and assessed risks of bias. The kappa scores for inter-reviewer agreement were substantial to almost perfect .
Strengths and Weaknesses of the Evidence:
The quality of the studies varied from the lack of adequate diagnosis or definition of controls to lack of adjustments for potential confounders. A wide range of participants, 6.3 percent to 78.8 percent, were diagnosed with PD according to radiographic, clinical or self-defined criteria with no distinction between aggressive or chronic periodontitis while 5.0 percent to 78.9 percent were diagnosed with MetS according to Adult Treatment Panel III (ATP III), National Cholesterol Education Program (NCEP), or International Diabetes Federation (IDF) criteria. Studies ranged from 45 to 62,254 participants. Egger’s test shows a small bias among the studies (p=0.081) with small studies reporting greater odds ratios for MetS; however, meta-regression shows the risk of bias scores was not significant (-0.054; p=0.363). Though they noted an increased prevalence of gingival inflammation in participants with MetS, the authors did not perform a meta-analysis regarding gingivitis because of limited studies available. There was moderate heterogeneity (I-squared=53.6 percent, p=0.004) overall with higher heterogeneity for cross-sectional than for case-control studies which had much smaller sample sizes. Only one longitudinal study, the most appropriate design, was available for observing PD and MetS disease processes, whereas all others were cross-sectional or case-control studies.
Implications for Dental Practice:
Practitioners may see in their practice an increased incidence of PD in patients who have MetS. Future longitudinal and treatment studies may investigate the effectiveness of preventing and/or treating MetS to reduce the risk of developing PD and vice versa and focus on identifying the shared risk factors, predisposing genetic variants, and health behavior and pathogenic factors between the two conditions. The prognosis in patients undergoing periodontal treatment may be improved by the management of MetS.
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