Functional near-infrared spectroscopy and vagus somatosensory evoked potentials add to the power of established parameters such as poor cognitive performance, dsyosmia and APOe genotype to predict cognitive decline over 8 years in the elderly

Abstract

Alzheimer’s dementia is the main cause of cognitive impairment in people over the age of 65, with Alzheimer’s disease starting presumably 10–15 years before the onset of clinical symptoms. It is therefore important to recognize dementia at an early stage and identify possible predictors. The existing methods, like different parameters of ß-Amyloid and Tau quantification in cerebrospinal fluid (CSF) or the living brain by measure of PET, are invasive and expensive. Therefore, the present study investigates the predictive value of a battery of clinical, neuropsychological, and blood parameters as well as two neurophysiological methods (functional near-infrared spectroscopy [fNIRS] and vagus somatosensory evoked potentials [VSEP]) which are easy to perform, less invasive and cost-efficient, for developing cognitive impairments in the elderly. In this longitudinal, prospective study, we enrolled 604 healthy participants between 70 and 77 years of age. The participants were invited back after a mean time interval of 3 years and 11 months, and after 7 years and 8 months, and their cognitive impairments were determined. Here we show that the development of cognitive impairments after approximately 8 years can be predicted not only by previously known risk factors such as ApoE4 risk alleles, dysosmia, or poor cognitive performance at baseline but that latency prolongation in the VSEP and altered functional activation patterns measured by NIRS at baseline also provide additional predictive value. We therefore suggest that both neurophysiological parameters, VSEP and NIRS, should be included in future studies, investigating the prediction of dementia.