Abstract
BackgroundDepression and chronic inflammatory medical conditions have been linked to impaired cognitive ability. However despite frequent comorbidity, their combined association with cognitive ability has rarely been examined. MethodsThis study examined associations between self-reported depression and chronic inflammatory diseases and their interaction with cognitive performance in 456,748 participants of the UK Biobank, adjusting for sociodemographic and lifestyle factors. Numbers with available data ranged from 94,899 to 453,208 depending on the cognitive test. ResultsSelf-reported depression was associated with poorer performance compared to controls in several cognitive tests (fully adjusted models, reaction time: B = 6.08, 95% CI = 5.09, 7.07; pairs matching: incidence rate ratio = 1.02, 95% CI = 1.02, 1.03; Trail Making Test B: B = 1.37, 95% CI = 0.88, 1.87; Digit Symbol Substitution Test (DSST): B = −0.35, 95% CI = −0.44, −0.27). Self-reported chronic inflammatory conditions were associated with slower reaction time (B = 3.79, 95% CI = 2.81, 4.78) and lower DSST scores (B = −0.21, 95% CI = −0.30, −0.13). No interaction effects were observed. DiscussionIn this large, population-based study we provide evidence of lower cognitive performance in both depression and a comprehensive category of chronic inflammatory conditions. Results are consistent with additive effects of both types of disorder on cognitive ability. Clinicians should be aware of such effects, particularly as cognitive impairment is linked to poorer disease outcomes and quality of life.
Highlights
Depression and certain medical conditions associated with chronic inflammation are associated with cognitive deficits [1,2], with inflammation proposed as a potential shared mechanism underlying these deficits [3]
Most other characteristics followed a relatively linear worsening pattern from controls to depression plus inflammation: depression and/or chronic inflammatory conditions were associated with greater deprivation, reduced educational attainment, decreased proportion of neversmokers, and worse unadjusted cognitive performance
We provide evidence of inverse associations of self-reported depression and chronic inflammatory conditions with cognitive performance in a large population-based cohort
Summary
Depression and certain medical conditions associated with chronic inflammation are associated with cognitive deficits [1,2], with inflammation proposed as a potential shared mechanism underlying these deficits [3]. Increased peripheral inflammatory markers (e.g., Interleukin-6 (IL-6), Creactive protein (CRP), tumour necrosis factor alpha (TNFα)) are associated with worse cognitive performance even in the absence of disease [6], consistent with a contribution of inflammation to the cognitive decline seen in depression [3]. Chronic inflammatory conditions such as RA and SLE are associated with higher prevalence of depression [7], and this comorbidity has been associated with worse disease outcomes, e.g., in remission rates, pain, and physical disability [8].
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