title: Elevated C-reactive protein associated with late- and very-late-onset schizophrenia in the general population: a prospective study.
abstract: BACKGROUND
  Individuals with autoimmune diseases and severe infections have persistent or acutely elevated inflammatory biomarkers and increased risk of schizophrenia. We tested the hypothesis that baseline elevated plasma levels of the inflammatory biomarker, C-reactive protein (CRP), associate with increased risk of late- and very-late-onset schizophrenia in the general population, and if such an association possibly is causal.
  
  
  METHODS
  We analyzed data from 78 810 men and women, aged 20-100 years, from 2 large population studies. Endpoints were hospitalization with schizophrenia and schizophrenia and schizophrenia-like psychosis combined. We performed prospective and cross-sectional analyses adjusted for potential confounders with up to 20 years of follow-up. Furthermore, we used genetic variants influencing plasma CRP levels to perform a Mendelian randomization study.
  
  
  RESULTS
  Age- and gender-adjusted hazard ratios vs individuals in the first quartile of CRP were 1.7 (95% CI: 0.3-8.9) for second quartile, 2.1 (0.4-10) for third quartile, and 11 (2.8-40) for fourth quartile individuals. The corresponding hazard ratio for fourth quartile individuals after multifactorial adjustment was 5.9 (1.4-24). Furthermore, individuals with vs without schizophrenia had 63% increased plasma levels of CRP (P = 1 × 10(-4)). Finally, when CRP was on a continuous scale, a doubling in CRP yielded an age- and gender-adjusted observational OR of 1.5 (1.3-1.8) and a corresponding causal OR of 1.4 (0.5-4.3) (observed vs causal: P = .89).
  
  
  CONCLUSIONS
  Baseline elevated plasma CRP is associated with a 6- to 11-fold increased risk of late- and very-late-onset schizophrenia in the general population. We cannot exclude that this is a causal association. These are novel findings.
authors.forename: Marie Kim
authors.initials: MK
authors.lastname: Wium-Andersen
authors.forename: David Dynnes
authors.initials: DD
authors.lastname: Ørsted
authors.affiliation: Boerge.Nordestgaard@regionh.dk.
authors.forename: Børge Grønne
authors.initials: BG
authors.lastname: Nordestgaard
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000032:analysis*; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D057182:Mendelian Randomization Analysis; D008875:Middle Aged; D011446:Prospective Studies; D011618:Psychotic Disorders / Q000097:blood* / Q000453:epidemiology* / Q000235:genetics; D012042:Registries; D012306:Risk; D012559:Schizophrenia / Q000097:blood* / Q000453:epidemiology* / Q000235:genetics; D055815:Young Adult
chemical_list: D002097:C-Reactive Protein
keywords: epidemiology; genetics; inflammation; schizophrenia