Speech as a means of monitoring cognitive function of elderly speakers

Abstract This study investigates the use of speech as an indicator of the onset of cognitive decline in the elderly. The analysis found features that correlate with the results of a clinical measure of cognitive function. Using a combination of temporal language features, such as pause and utterance duration, 76% classification accuracy was achieved. While no significant results were found for ASR experiments, vowel duration, on average, increased by 17% for subjects with cognitive impairment compared to those without. The results from this study introduce the concept of longitudinal studies into aging using speech as a window into cognitive function. Index Terms: cognitive decline; elderly, temporal features 1. Introduction The world’s population is growing older. In the next 50 years, the number of older people is forecast to quadruple, growing from about 600 million to almost 2 billion people [1]. With the prospect of people living longer there has been concerted efforts to provide healthcare at appropriate times to allow the elderly to live as independently as possible, for as long as possible [2], [3]. Remote monitoring of older people in their homes may enable early detection of some of the problems associated with old age, such as propensity to falls and social isolation along with decline in cognitive function. Once Mild Cognitive Impairment (MCI) has set in it is usually too late to implement any cognitive training schema that could help. The biggest limiting factor to independence in the elderly is impaired cognitive function and its consequences. Such consequences include: accident proneness (falls, burns, bruising and cuts), self-neglect (missed medication, poor nutrition, poor hygiene), loss of initiative, diminished repertoire of activities and low mood. The assessment of cognitive function is expensive and labour intensive and hence non-viable for all but a tiny fraction of the elderly. In addition the elderly is a population traditionally highly averse to using new technology, which makes technical solutions to the assessment of cognitive function more difficult. Speech may provide a cost effective, easily implementable means of monitoring and assessing cognitive function. The disproportionate vulnerability of the brain’s frontal lobe to aging means that attention and executive function predominate in cognitive impairment having major detrimental effects on memory, attention, planning, initiative, mood vigilance as well as self-, safety-, and environmental awareness. One of the standard clinic tools used by psychologists for assessing cognitive function is the Mini Mental State Examination (MMSE) [5]. This consists of a questionnaire that rates cognitive function out of 30. MMSE scores of less than 27 are generally considered as possibly cognitively impaired by clinicians. Previous studies have found spoken language markers to be indicative of Mild Cognitive Impairment (MCI) [6]. Roark et al found standardized pause rate (the ratio of words uttered to the number of pauses uttered) to be statistically different for two sets of elderly speakers; using a Clinical Dementia Rating (CDR), the cohort was separated into those with MCI and those without. While other speech duration parameters were investigated in the study including verbal rate (number of words per second), phonation rate (proportion of total time spent speaking) and mean duration of pauses, none of these were found be significantly different for the two populations. Speech has also been shown to be an indicator of other neuro-degenerative diseases, such as schizophrenia [7]. Stassen et al looked at temporal parameters extracted from read speech from known sufferers of the disease and matched controls. In this case the correlation with this type of cognitive impairment and temporal features such as mean pause duration is attributed to the negative symptoms of the disease. These include affective flattening, blunted affect emotional dullness, poverty of speech and psycho-motor retardation. A recent study carried out by Lieberman et al [8], investigated audio recorded from climbers ascending Mount Everest. The effect of altitude on the cognitive function of climbers was used to simulate that experienced by astronauts in space. Astronauts' cognition is impacted by hypoxic and cosmic ray-induced insult to the brain, as well as degraded cognitive performance resulting from task difficulty. The authors found acoustic measures of temporal characteristics of speech can be used to monitor cognitive impairment. This study focuses on identifying the onset of cognitive decline from features that can readily be extracted from speech. Experimentation includes investigating speech from a temporal feature perspective and from an acoustic perspective. Speech is a non-intrusive means of data collection and speech centred applications, particularly telephony based, can be implemented using technology that is familiar to the potential users.