title: The longitudinal associations between C-reactive protein and depressive symptoms: evidence from the English Longitudinal Study of Ageing (ELSA).
abstract: OBJECTIVE
  The inflammatory marker C-reactive protein (CRP) is associated with depression. We examined the directional relations between CRP and symptoms of depression among older adults.
  
  
  METHODS
  The sample consisted of 3397 participants from the English Longitudinal Study of Ageing, a prospective study of community-dwelling older adults. CRP and depressive symptoms were measured at baseline and follow-up. A high CRP level was dichotomized as >3 mg/L. Elevated depressive symptomatology was defined as ≥4 using the 8-item Center for Epidemiologic Studies Depression Scale. Logistic regressions computed the association between high CRP levels at baseline with elevated depressive symptoms at follow-up, and vice versa.
  
  
  RESULTS
  After adjusting for baseline depressive symptoms, baseline high CRP levels were associated with subsequent elevated symptoms of depression (OR = 1.49; 95% CI, 1.19-1.88). This relationship was no longer significant after simultaneous adjustments for metabolic and health variables. In the other direction, after adjusting for baseline CRP levels, baseline elevated depressive symptoms was not associated with subsequent high CRP levels (OR = 1.12; 95% CI, 0.88-1.42).
  
  
  CONCLUSIONS
  High CRP levels at baseline are related to elevated depressive symptomatology at follow-up due to clinical factors. No association was found in the opposite direction.
authors.affiliation: Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada.|Douglas Mental Health University Institute, Montreal, Quebec, Canada.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Au
authors.affiliation: Douglas Mental Health University Institute, Montreal, Quebec, Canada.|Department of Psychiatry, McGill University, Montreal, Quebec, Canada.
authors.forename: Kimberley J
authors.initials: KJ
authors.lastname: Smith
authors.affiliation: Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada.|Douglas Mental Health University Institute, Montreal, Quebec, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Gariépy
authors.affiliation: Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada.|Douglas Mental Health University Institute, Montreal, Quebec, Canada.|Department of Psychiatry, McGill University, Montreal, Quebec, Canada.|Montreal Diabetes Research Center, Montreal, Quebec, Canada.
authors.forename: Norbert
authors.initials: N
authors.lastname: Schmitz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D015415:Biomarkers / Q000378:metabolism; D002097:C-Reactive Protein / Q000032:analysis*; D003866:Depressive Disorder / Q000378:metabolism*; D004739:England; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein
keywords: C-reactive protein; depression; inflammation; longitudinal; older adults