School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK.
Experimental Psychology Department, University College London, London, UK.
Int J Geriatr Psychiatry. 2024 Jun;39(6):e6112. doi: 10.1002/gps.6112.
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.
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.
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.
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.
阿尔茨海默病（AD）患者的意识水平和内容会发生变化，但关于临床前 AD 和轻度认知障碍（MCI）患者的意识生物标志物的研究较少。本研究旨在探讨 MCI 患者的意识水平是否降低。
对包含 83 名 MCI 患者和 83 名年龄匹配对照者的多中心脑磁图（MEG）数据集 BIOFIND 进行分析。通过计算θ-α 比（TAR）评估觉醒（和困倦）水平。使用 Lempel-Ziv 算法（LZ）量化脑活动的信息含量，LZ 值越高表示复杂度越高，意识水平可能越高。
与对照组相比，MCI 组的 LZ 值较低，表明 MCI 患者的意识水平降低。与对照组相比，MCI 组的 TAR 值较高，表明 MCI 患者的觉醒水平（即困倦增加）降低。LZ 还与简易精神状态检查（MMSE）评分相关，表明 MCI 患者认知障碍与意识水平之间存在关联。
在 MCI 中可以看到意识和觉醒水平下降。随着 MMSE 评分所衡量的认知障碍恶化，意识和觉醒水平降低。这些发现强调了使用生物标志物监测意识如何有助于理解和管理 AD 临床前阶段的损害。需要进一步研究来探索从 MCI 进展为痴呆的人与未进展为痴呆的人之间的意识标志物，以及在中度和重度 AD 患者中，以促进以患者为中心的护理。
