Early detection of Mild Cognitive Impairment (MCI) in older adults is pivotal for dementia intervention. As a faithful indicator of brain function, speech and language offer an ideal non-invasive monitoring window. This study reviews neurophysiological foundations and assessment paradigms to analyze MCI-related anomalies across acoustic, semantic, and syntactic dimensions. Addressing the limitations of purely structural linguistic analysis, we propose redefining speech and language as biosocial markers. This framework integrates emotional prosody and pragmatic mechanisms (e.g., conversational alignment and repair) to capture early, occult social cognitive deficits. Finally, we discuss the technical and ethical challenges of interactive signal acquisition and envision the potential for home-based ecological monitoring. This multidimensional approach provides a theoretical framework with enhanced ecological validity and clinical interpretability for precision MCI screening.