title: Factor analysis of risk variables associated with low-grade inflammation.
abstract: BACKGROUND
  Chronic subclinical inflammation, manifesting as elevated levels of inflammatory markers such as C-reactive protein (CRP), predicts future atherothrombotic events. The pathophysiology of low-grade inflammation is complex, and multiple intercorrelated conditions have been associated with elevated CRP.
  
  
  METHODS
  Principal factor analysis was used to investigate clustering of variables associated with elevated CRP using data from 1435 subjects without known coronary disease. Components of the metabolic syndrome, uric acid, liver enzymes, pulmonary function tests, smoking status, cardiorespiratory fitness (measured by maximal treadmill test), and high-sensitivity C-reactive protein were determined in each subject.
  
  
  RESULTS
  Factor analysis identified three factors, which explained 51.0% of the total variance in the dataset (24.4% factor 1, 17.3% factor 2, and 9.3% factor 3). Based on factor loadings of >or=0.5, these factors were interpreted as (1) "metabolic factor" including BMI, fasting glucose, HDL cholesterol, triglycerides, systolic blood pressure, and uric acid; (2) a cardiorespiratory factor that included fitness level, forced expiratory volume in 1s and sex; and (3) "smoking" factor that included cigarette smoking and age. Each of these factors was significantly associated with the presence of high-risk CRP (>or=3mg/L) in the study population. The ability of a multivariate model that included these three factors to predict high-risk CRP was comparable to a model containing the original 10 variables (area under the receiver-operator characteristics curve 0.7 vs. 0.72, respectively).
  
  
  CONCLUSIONS
  Metabolic perturbations, cardiorespiratory fitness, and smoking are separate and largely independent factors in the pathophysiology of chronic, low-grade inflammation.
authors.affiliation: Department of Cardiology, Rambam Medical Center and the Ruth and Bruce Rappaport School of Medicine, Technion-Israel Institute of Technology, Haifa, Israel. daronson@tx.technion.ac.il
authors.forename: Doron
authors.initials: D
authors.lastname: Aronson
authors.forename: Ophir
authors.initials: O
authors.lastname: Avizohar
authors.forename: Yishai
authors.initials: Y
authors.lastname: Levy
authors.forename: Peter
authors.initials: P
authors.lastname: Bartha
authors.forename: Giris
authors.initials: G
authors.lastname: Jacob
authors.forename: Walter
authors.initials: W
authors.lastname: Markiewicz
mesh_terms: D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000276:immunology*; D005080:Exercise Test; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007249:Inflammation / Q000276:immunology*; D008297:Male; D024821:Metabolic Syndrome / Q000276:immunology*; D008875:Middle Aged; D012129:Respiratory Function Tests; D012907:Smoking / Q000276:immunology
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein