title: Systemic inflammation, depression and obstructive pulmonary function: a population-based study.
abstract: BACKGROUND
  Levels of Interleukin-6 (IL-6) and C-creative protein (CRP) indicating systemic inflammation are known to be elevated in chronic diseases including chronic obstructive pulmonary disease (COPD) and depression. Comorbid depression is common in patients with COPD, but no studies have investigated whether proinflammatory cytokines mediate the association between pulmonary function and depressive symptoms in healthy individuals with no known history of obstructive pulmonary diseases.
  
  
  METHODS
  In a population-based sample (n = 2077) of individuals aged 55 and above with no known history of obstructive pulmonary disease in the Singapore Longitudinal Ageing Study (SLAS), we analyzed the relationships between IL-6 and CRP, depressive symptoms (GDS-15 ≥5) and obstructive pulmonary function (FEV1% predicted and FEV1/FVC% predicted).
  
  
  RESULTS
  High serum levels of IL-6 and CRP were associated with greater prevalence of depressive symptoms (p < 0.05). High IL-6, high CRP and depressive symptoms were independently associated with decreased FEV1% predicted and FEV1/FVC% predicted after adjusting for smoking status, BMI and number of chronic inflammatory diseases. Increasing grades of combination of inflammatory markers and/or depressive symptoms was associated with progressive increases in pulmonary obstruction. In hierarchical models, the significant association of depressive symptoms with pulmonary obstruction was reduced by the presence of IL-6 and CRP.
  
  
  CONCLUSIONS
  This study found for the first time an association of depressive symptoms and pulmonary function in older adults which appeared to be partly mediated by proinflammatory cytokines. Further studies should be conducted to investigate proinflammatory immune markers and depressive symptoms as potential phenotypic indicators for chronic obstructive airway disorders in older adults.
authors.affiliation: Gerontological Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, and Department of Psychological Medicine, National University Hospital System, NUHS Tower Block, 9th Floor, 1E Kent Ridge Road, 119228 Singapore, Singapore.
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Lu
authors.forename: Lei
authors.initials: L
authors.lastname: Feng
authors.forename: Liang
authors.initials: L
authors.lastname: Feng
authors.forename: Ma Shwe
authors.initials: MS
authors.lastname: Nyunt
authors.forename: Keng Bee
authors.initials: KB
authors.lastname: Yap
authors.forename: Tze Pin
authors.initials: TP
authors.lastname: Ng
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D015897:Comorbidity; D003863:Depression / Q000097:blood* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D015850:Interleukin-6 / Q000097:blood*; D008173:Lung Diseases, Obstructive / Q000097:blood* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests / Q000706:statistics & numerical data; D018570:Risk Assessment; D012846:Singapore / Q000453:epidemiology; D018746:Systemic Inflammatory Response Syndrome / Q000097:blood* / Q000453:epidemiology
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein