Inflammatory markers in late-life depression: results from a population-based study.
BACKGROUND
Previous studies have reported conflicting results concerning the association between several inflammatory markers and depression. The association between inflammation and depression may depend on the presence of specific chronic diseases or be relevant in specific sub-groups of depressed patients only.


OBJECTIVE
To assess associations between inflammatory markers and depression in older people, taking account of confounding and effect-modifying factors.


METHODS
Population-based study of 1285 participants of the Longitudinal Aging Study Amsterdam, aged 65 and over. Plasma concentrations of Interleukin-6 (IL-6) and C-reactive protein (CRP) were measured. Major depression (first- or recurrent episode) and sub-threshold depression were assessed. Associations were adjusted for confounding variables. Associations with inflammatory markers were further studied with regard to severity and duration of depression, and with regard to specific depressive symptoms.


RESULTS
High levels of IL-6 (above 5 pg/mL) were associated with major depression (odds ratio 2.49 (1.07-5.80), both in recurrent and first episodes. No significant effect of either one of the markers on specific symptom dimensions of depression was found. Mildly elevated plasma levels of CRP (above 3.2 mg/L) were associated with higher CES-D scores, but not after correction for the confounding effect of age and chronic diseases.


CONCLUSIONS
The cross-sectional design limits conclusions regarding causality.


CONCLUSIONS
A high plasma level of IL-6, but not CRP, is associated with an increased prevalence of major depression in older people, independent of age, chronic diseases, cognitive functioning and anti-depressants. Present results suggest new directions for clinical research into the prevention of physical consequences of depression.
Bremmer
M A
MA
Department of Psychiatry, VU University Medical Center, Amsterdam, The Netherlands. ma.bremmer@vumc.nl
Beekman
A T F
AT
Deeg
D J H
DJ
Penninx
B W J H
BW
Dik
M G
MG
Hack
C E
CE
Hoogendijk
W J G
WJ
D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood*; D002097:C-Reactive Protein / Q000032:analysis*; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006306:Health Surveys; D006801:Humans; D007249:Inflammation / Q000097:blood; D015850:Interleukin-6 / Q000032:analysis*; D008137:Longitudinal Studies; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors
D015415:Biomarkers; D015850:Interleukin-6; D002097:C-Reactive Protein