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Nascimento GG, Leite FR et al. J Clin Periodontol 2015;42: 495–505

When a RR (relative risk) >1 means that periodontitis is more likely to occur in the developing periodontitis group, and a 95% CI (confidence interval) indicates there is a 95% chance that the mean lies within that interval. In this systematic review, associations were sought between those becoming overweight and also those becoming obese, and new cases of periodontitis. By examining incidence cases, including only prospective longitudinal studies omitting cross-sectional studies, biased causal effects are avoided. Some 1,398 articles were whittled down to five and these were included in the meta-analysis (n = 42,198 subjects). The Newcastle–Ottawa scale was used to assess the quality of the studies; these were judged to be moderate to high methodological quality. Although there was an association between becoming overweight and becoming obese and incident periodontitis, the investigators were aware that quantifying these measurements are problematic. The relative risk was small but important, as periodontitis is common.