title: Unhealthy lifestyle may increase later depression via inflammation in older women but not men.
abstract: Depression and inflammatory markers have a reliable cross-sectional association although less is known about the prospective relationship. The current study investigated whether pro-inflammatory markers are prospectively associated with depression, and whether indicators of unhealthy lifestyle, physical health and psychosocial functioning may drive this association. Participants were drawn from the Hunter Community Study, a community-dwelling cohort of individuals aged 55-85 years (N = 1410). Participants completed baseline physiological assessment, health-related questionnaires, and blood sampling for the analysis of inflammatory markers, C-reactive protein (CRP) and interleukin (IL)-6. Participants completed the same depressive symptom questionnaire again after 3.5-5.5 years. Depression outcomes at follow-up were analysed dichotomously using established scale cut-off scores and continuously as a "residual score", representing the variation in follow-up depressive symptoms not explained by baseline symptoms and age. Analyses were conducted on males and females separately. At baseline, indicators of unhealthy lifestyle, physical health and psychosocial functioning were associated with depressive symptoms and inflammatory markers. For males, there were no relationships between inflammatory markers and follow-up depression outcomes. In females, IL-6 was significantly associated with depression outcomes in univariate, but not multivariate analyses. However, IL-6 significantly mediated the association between the predictors of waist-to-hip ratio, smoking and psychological coping at baseline, and follow-up depression outcomes. The results support the inflammatory hypothesis of depression, although females may be more vulnerable to effects. The findings raise the possibility that unhealthy lifestyle and psychosocial stress may drive inflammation and subsequent depressive symptoms.
authors: Priority Research Centre for Translational Neuroscience and Mental Health, Faculty of Health, University of Newcastle, New South Wales, Australia. Electronic address: sarah.hiles@uon.edu.au.
authors: Sarah A
authors: SA
authors: Hiles
authors: Priority Research Centre for Translational Neuroscience and Mental Health, Faculty of Health, University of Newcastle, New South Wales, Australia.
authors: Amanda L
authors: AL
authors: Baker
authors: Immunology, Hunter Area Pathology Service, John Hunter Hospital, New South Wales, Australia.
authors: Theo
authors: T
authors: de Malmanche
authors: Centre for Clinical Epidemiology and Biostatistics, Faculty of Health, University of Newcastle, New South Wales, Australia; Hunter Medical Research Institute, John Hunter Hospital, New South Wales, Australia.
authors: Mark
authors: M
authors: McEvoy
authors: Immunology and Infectious Diseases Unit, Medical and Interventional Service, John Hunter Hospital, New South Wales, Australia.
authors: Michael
authors: M
authors: Boyle
authors: Centre for Clinical Epidemiology and Biostatistics, Faculty of Health, University of Newcastle, New South Wales, Australia; Hunter Medical Research Institute, John Hunter Hospital, New South Wales, Australia.
authors: John
authors: J
authors: Attia
mesh_terms: D000368:Aged; D001315:Australia / Q000453:epidemiology; D002097:C-Reactive Protein / Q000378:metabolism; D003430:Cross-Sectional Studies; D003863:Depression / Q000097:blood / Q000453:epidemiology* / Q000523:psychology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000453:epidemiology*; D015850:Interleukin-6 / Q000097:blood; D008019:Life Style; D008297:Male; D008875:Middle Aged; D011788:Quality of Life / Q000523:psychology; D012111:Residence Characteristics; D012189:Retrospective Studies; D057566:Self Report; D012727:Sex Characteristics
chemical_list: D015850:Interleukin-6; D002097:C-Reactive Protein
keywords: C-reactive protein; Cohort; Depression; Inflammation; Interleukin; Prospective