Elevated C-reactive protein associated with late- and very-late-onset schizophrenia in the general population: a prospective study.
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.


METHOD
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).


CONCLUSION
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.
['Wium-Andersen|Marie Kim|MK|', 'Ørsted|David Dynnes|DD|', 'Nordestgaard|Børge Grønne|BG|']
D000328:Adult D017668:Age of Onset D000368:Aged D000369:Aged, 80 and over D002097:C-Reactive Protein D003430:Cross-Sectional Studies D003718:Denmark D005260:Female D005500:Follow-Up Studies D006801:Humans D008297:Male D057182:Mendelian Randomization Analysis D008875:Middle Aged D011446:Prospective Studies D011618:Psychotic Disorders D012042:Registries D012306:Risk D012559:Schizophrenia D055815:Young Adult
schizophrenia genetics epidemiology inflammation