Neural markers of reduced arousal and consciousness in mild cognitive impairment

Objectives People with Alzheimer's Disease (AD) experience changes in their level and content of consciousness, but there is little research on biomarkers of consciousness in pre‐clinical AD and Mild Cognitive Impairment (MCI). This study investigated whether levels of consciousness are decreased in people with MCI. Methods A multi‐site site magnetoencephalography (MEG) dataset, BIOFIND, comprising 83 people with MCI and 83 age matched controls, was analysed. Arousal (and drowsiness) was assessed by computing the theta‐alpha ratio (TAR). The Lempel‐Ziv algorithm (LZ) was used to quantify the information content of brain activity, with higher LZ values indicating greater complexity and potentially a higher level of consciousness. Results LZ was lower in the MCI group versus controls, indicating a reduced level of consciousness in MCI. TAR was higher in the MCI group versus controls, indicating a reduced level of arousal (i.e. increased drowsiness) in MCI. LZ was also found to be correlated with mini‐mental state examination (MMSE) scores, suggesting an association between cognitive impairment and level of consciousness in people with MCI. Conclusions A decline in consciousness and arousal can be seen in MCI. As cognitive impairment worsens, measured by MMSE scores, levels of consciousness and arousal decrease. These findings highlight how monitoring consciousness using biomarkers could help understand and manage impairments found at the preclinical stages of AD. Further research is needed to explore markers of consciousness between people who progress from MCI to dementia and those who do not, and in people with moderate and severe AD, to promote person‐centred care. Key points Consciousness and Arousal in MCI: This study found that patients with Mild Cognitive Impairment (MCI) show reduced neural complexity and arousal levels, as measured by LZsum and theta‐alpha ratio (TAR), respectively. These reductions correlate with the severity of cognitive impairment. Correlation with Cognitive Tests: There is a significant correlation between the LZsum and TAR biomarkers and the Mini‐Mental State Examination (MMSE) scores, both overall and within the MCI group, indicating that these neural markers can reflect the extent of cognitive decline. Potential Early Indicators: The biomarkers used in the study not only showed a significant difference between MCI patients from controls, but are also sensitive to the degree of cognitive impairment, supporting their use in mon