Oropharyngeal dysphagia in elderly population suffering from mild cognitive impairment and mild dementia: Understanding the link
Introduction
Measurable changes in cognition occur with normal ageing. The most important changes are declines in cognitive tasks that require one to quickly process or transform information such as in making a decision, including in measures of speed of processing, working memory, and executive cognitive function [1].
Ageing is associated with a slowing of the swallow response in the pharynx due to both central and peripheral factors. These changes may have an impact on the movement of food bolus. It is well described in the literature that tongue pressure declines with age [2]. Lack of muscle strength complicated by the decline in sensory informations such as olfaction and taste and/or by a poor dental status observed in the elderly makes swallowing more difficult. This scenario is known as presbyphagia and is more commonly seen after the age of 80 [2]. Presbyphagia, in itself, does not give rise to pathological changes in swallowing but it is a risk factor that can lead to Oropharyngeal Dysphagia (OD) [3]. In fact, the prevalence of OD has been calculated in independently living elderly persons with rates between 30% and 40%, 44% in those admitted to geriatric acute care and 60% in institutionalised elderly patients [[4], [5], [6]]. Unfortunately, in a presbyphagic scenario, patients affected by dementia easily develop OD during the course of their disease.
Generally, swallowing impairment in Alzheimer's and other forms of dementia is well described for the severe or moderate stages of the diseases [7]. While in the earlier stages it is often underdiagnosed [8]. Dysphagia related to Alzheimer's dementia (AD) is caused by involvement of the cortical areas of the brain for swallowing and due to the presence of delayed swallowing reflex and oropharyngeal problems. Recently, in 2019, Oszurecki reported this in the early stage of disease too [8].
In other forms of severe dementia, OD is caused by various other alterations in the brain. For example, Suh et al. in 2009 reported, that, Vascular Dementia (VAD) patients showed either multiple strokes or periventricular white matter involvement of portions of the brain sometimes which may even be in a single strategic area. (9 Suh). These alterations can lead to motor impairment in swallowing resulting in dysphagia with difficulties in mastication and bolus formation [9].
In addition, in cases of Fronto Temporal Dementia (FTD), it is described that hypothalamic degeneration with the disintegration of connections between the hypothalamus and the orbitofrontal cortex/reward pathways is what causes eating abnormalities.
In subjects suffering from Primary Progressive Aphasia (PPA) presence of high levels of the eating peptides and overall Agouti-related-peptide (AgRP) is observed. Agouti-related-peptide is a strong promoter of food intake [10]. These alterations cause changes in eating habits, hyperorality and disinhibition during the meal [10]. Langmore in 2007 while analysing swallowing behaviours in patients suffering from FTD and PPA showed that these patients presented with compulsive eating behaviours often associated with minimal endoscopic signs of OD. This association favoured an increased risk of aspiration too [11].
Interestingly, the patients who are suffering from Mild Cognitive Impairment (MCI) with seemingly good swallowing or chewing ability, as perceived by their own caregivers [12], also had impairment of oral diadokokinesis and spilling of food. This is caused mainly by impaired oral motor skills such as poor lip function and has been well described for this class of patients [13]. In addition, Delwel reported that MCI patients evaluated in his study showed a limited active maximum mouth opening (<40 mm) [12] and this fact can play a pathological role in swallowing or chewing.
The purpose of our study was to evaluate whether OD is already present in elderly patients suffering from mild or very slight cognitive decline and if this was related to further risk, even fatal, for the patient.
Section snippets
Patients and methods
We collected retrospective data of patients managed in our department for cognitive decline and suspected OD (U.O. Foniatria, Dipartimento di Riabilitazione, ASL Lecce, Italy) in the last two years from 1st of January 2018 to 31st of December 2019.
All patients who were 65 years or older with either minimal or mild cognitive impairment presenting to us with suspected OD were included in the study. Patients who were younger than 65 years, with a clinical history of cervical spine pathologies,
Results
Out of 708 patients who visited us for a decline in cognitive function along with suspected OD in the last two years (from 01 January 2018 to 31 December 2019) only 52 patients were strictly adhering to the criteria of this study. The sample size of 52 is in line with recently published literature as well as giving us an insight into the pathophysiological changes of swallowing seen in persons affected by cognitive decline [21,22]. Mean age of our patients was 75.9 years (±8.6) range
Discussion and conclusion
On the basis of the MDADI results observed in our study, it was clear that most of our patients were unable to recognise their swallowing disabilities although the degree of cognitive decline was very mild. Because of this, there were no limitations in the daily activities and food intake of these patients. All the patients described in this study were referred to our department principally for a minimal decrease in memory functions or difficulties in the semantic production of the language but
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