Is low-grade inflammation related to cognitive performance during a sustained attention task in depression? – A case-control study

This study aimed to investigate the associations between inflammatory cytokines and cognitive performance in individuals with depression compared to healthy controls, while accounting for variables, such as perceived fatigue, BMI, and age. Individuals diagnosed with depression (n = 23) and healthy controls (n = 31) were included in the study. A 15-minute sustained attention task (subtest of the Test Battery for Attention, version 2.3.1) was administered with concurrent electroencephalographic recordings to evaluate P300 amplitude and latency. Peripheral inflammation was assessed by measuring IL-6, IL-1β, and TNF-α levels. Perceived fatigue was assessed using the German version of the Fatigue Impact Scale. Generalized linear models (GLM) were used to evaluate the main aims of the study. Results indicated that depression was associated with reduced P300 amplitudes (p = 0.011), and age was significantly associated with P300 amplitude, with older participants showing reductions (p = 0.016). However, no significant effects of inflammatory markers on P300 components were found. While no group differences were observed in the total number of hits, both perceived fatigue (p = 0.033) and TNF-α (p = 0.007) were significantly associated with hit accuracy. A post-hoc mediation analysis explored that perceived fatigue mediates the relationship between depression and number of hits. These findings suggest that low-grade inflammation may not directly influence P300 components, though inflammation and fatigue appear linked to accuracy deficits. Finally, the impact of depression on the number of hits is primarily mediated by perceived fatigue, suggesting that fatigue is a crucial factor in how depression affects cognition.