Refining exposure definitions for studies of periodontal disease and systemic disease associations.

Background: Substantial variation exists in reported associations between periodontal infections and cardiovascular disease. Imprecise periodontal exposure definitions are possible contributors to this variability. We studied appropriate exposure definitions for studying associations between clinical periodontal disease (PD) and systemic disease.
Methods: Data originate from men and women aged 20-79 enrolled in the Study of Health in Pomerania (SHIP) from 1997-2001. Age and sex-adjusted correlation analysis identified PD definitions with the highest cross-sectional associations with three subclinical markers of systemic disease: plasma fibrinogen (n = 3481), serum hemoglobin A1c (HbA1c) (n = 3480), and common carotid artery intima-media thickness (c-IMT) (n = 1745, age > or = 45).
Results: In men and women, percent of sites with attachment loss (AL) > or =6 mm and tooth loss both revealed the highest correlation with HbA1c (rho = 0.11; several other definitions related similarly), while the strongest fibrinogen correlation was observed with percent of sites with pocket depth > or =3 mm (rho = 0.19). Findings for c-IMT among men were strongest for percent of sites with AL > or =6 mm (rho = 0.14; several other definitions related similarly) while among women, percent of sites with pocket depth > or =5 or 6 mm had the highest observed correlation (rho = 0.13).
Conclusions: A range of near optimal definitions varied according to gender and whether the systemic disease marker reflected an acute or chronic situation. Pocket depth was more strongly correlated with the acute marker fibrinogen while attachment and tooth loss tended to be more strongly correlated with the chronic markers, HbA1c, and c-IMT. These findings can be useful in designing future studies investigating the association between PD and systemic disease.