Neutrophil-to-Lymphocyte Ratio, Bone Marrow, and Visceral Fat Metabolism as Predictors of Future Cardiovascular Disease in an Asymptomatic Healthy Population

<b>Background/Objectives:</b> The neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, is a known predictor of cardiovascular disease and overall mortality. We examined the relationship between the NLR and the metabolic activity of hematopoietic organs and visceral fat, and their association with the risk of atherosclerotic cardiovascular disease (ASCVD) in an asymptomatic healthy population. <b>Methods:</b> We retrospectively analyzed individuals who underwent F-18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) as part of their health check-ups. Metabolic activity was quantified using standardized uptake values (SUVs) from the lumbar vertebral bone marrow, spleen, visceral, and subcutaneous fat, normalized to target-to-background ratios (TBRs) using the superior vena cava. NLR was calculated from absolute neutrophil and lymphocyte counts. Correlations between NLR, clinical parameters, organ TBRs, and ASCAD risk were analyzed. <b>Results:</b> Among 303 participants from three hospitals, the median NLR was 1.5 (range: 0.5-5.55). NLR showed weak correlation with the TBRs of bone marrow, visceral fat, and subcutaneous fat, as well as high-density lipoprotein cholesterol and body mass index (BMI). In logistic regression analysis adjusted for age and sex, BMI and the TBRs of bone marrow and visceral fat were independent predictors of elevated NLR (≥ 1.5). When integrating these parameters, NLR demonstrated strong predictive performance for identifying a high ASCVD risk (≥20% over 10 years), with an area under the curve of 0.826. <b>Conclusions:</b> In an asymptomatic healthy population, NLR is associated with FDG metabolic parameters of hematopoietic organs and adipose tissue. These combined measures may serve as valuable marker for identifying individuals at elevated ASCVD risk.