Higher depression scores in cognitively unimpaired individuals affect event‐related potentials similar to those of MCI

Abstract Background Depression is common among seniors, both cognitively unimpaired (CU) and in individuals with Mild Cognitive Impairment (MCI). Electroencephalography (EEG) event‐related Potentials‐P300 is one of the most commonly used electrophysiological parameter associated with cognition. This study aimed to investigate P300 mean amplitude differences between CU individuals and those with MCI, with and without depressive symptoms. Method The study included 20 CU individuals with depression [CU‐Dep(+)], 21 MCI patients [MCI‐Dep(+)] with depression, 20 CU individuals without depression [CU‐Dep(‐)] and 22 MCI patients [CU‐Dep(‐)] without depression. Geriatric Depression Scale (GDS) ≥14, was the cut‐off score for classification of Dep (+) or Dep (‐). CU seniors had no significant neurological abnormality or global cognitive impairment. Participants with MCI had cognitive impairment as defined with performances ≥1.5 standard deviations below for age‐and education‐matched controls and with no impairment of daily‐living activities. The ERPs were recorded with a visual classical oddball paradigm, mean P300 amplitudes were measured in the 250‐550ms time window. Result The repeated‐measures ANCOVA showed no effect of age and education on P300 but a LOCATION x GROUP interaction [F(6,158) = 2.56,p = 0.035) and main GROUP effect [F(3,79) = 2.56,p = 0.003). Post‐hoc analysis revealed CU‐Dep(‐) had higher P300 amplitudes than MCI‐Dep(+). Moreover, CU‐Dep(+) had lower P300 amplitudes than CU‐Dep(‐) in frontal electrode location. Although there were no significant results, there were a gradual decline trend from CU‐Dep(‐) to MCI‐Dep(+)(Figure 1., Table 2.). Conclusion The current study showed reduced P300 amplitudes in CU and MCI groups with depression as compared to those without depression. The P300 potential may be a useful tool to determine possible changes or impairments due to sub‐threshold depressive symptoms. However, the lack of significant difference between CU‐Dep(‐) and MCI‐Dep(‐) shows us that the P300 amplitude difference may not always be associated with cognitive status, but may also be associated with depressive symptoms. Thus, it is necessary to consider the depressive symptoms of the participants in cognitive EEG studies.