Salivary Lysozyme Levels Predict Increased Risk of Cardiovascular Mortality in 18 Years of Follow-up

Objectives: Infections and innate immune activation may contribute to inflammation in atherogenesis. Salivary lysozyme (SLZ) is a bactericidal enzyme expressed by the innate immune system that hydrolyzes muramyl dipeptide in peptidoglycan of the bacterial cell walls. Thus SLZ may represent innate immune activation via bacterial infection. The objective of this study is to investigate whether SLZ as a marker for innate immune activation could predict CVD mortality.

Methods: The data on 471 subjects participating in Kuopio Oral Health and Heart study without any missing values were analyzed utilizing proportional hazard regression methods to examine the association between baseline SLZ and CVD mortality (median follow-up=18.8 years). of the We divided the whole cohort by the SLZ levels into tertiles and the mortality associated with the third tertile was compared to that of the reference group. As the data dictated, the two lower tertiles comprised the reference group. We adjusted established confounders such as age, sex, smoking status, hypertension, diabetes, Total/HDL cholesterol ratio, and income. We additionally adjusted for CRP to control for the non-infectious inflammation from metabolism.

Results: The multivariate adjusted hazard ratio for CVD mortality was 1.74; (the 95% confidence interval 1.1 - 2.76; p-value = 0.02). Adjusting for systemic inflammatory marker C-reactive protein (CRP) attenuated the association of SLZ with CVD mortality slightly (HR=1.68) but the association remained statistically significant (p=0.03).

Conclusions: Innate immune activation assessed by SLZ was associated with increased risk of CVD mortality by a significant 74% and this relationship was independent of metabolic inflammation.