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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 1  |  Page : 14-18

Identifying multiple domain memory impairment in high-risk group for Alzheimer's disorder


Department of Clinical Psychology, Amity University, Kolkata, West Bengal, India

Date of Web Publication16-Aug-2019

Correspondence Address:
Dr. Susmita Halder
Department of Clinical Psychology, Amity University, Kolkata, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jgmh.jgmh_4_19

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  Abstract 


Introduction: Occasional lapses in memory in elderly people are often considered as normal aging process and not a warning sign of serious mental deterioration or Alzheimer's disease (AD). When memory loss becomes so pervasive and severe that it disrupts daily activities, it becomes a signal for early AD. As the disease is irreversible and progressive in nature, identification of persons with high risk of developing AD is becoming a priority. The objective of this study was to identify and characterize the deficits in the memory performance of patients who presented with memory difficulties, without any other significant cognitive decline, and identified with high risk. Subject and Methods: Consecutive patients of both sexes in the age range of 55–70 years, who presented with problem in memory, were screened on the Mini–Mental State Examination and further assessed on the Dementia Rating Scale. Patients identified with high risk for AD were assessed for their memory profile using the PGI Memory Scale and further compared with healthy controls. Results: The high-risk group performed significantly lower than controls in domains of recent memory, delayed recall, verbal retention for dissimilar pairs, visual retention, and recognition. Conclusion: Multiple memory domains are affected in high-risk group for AD. Although they did not qualify to be diagnosed with AD, their memory profile is distinct with healthy controls and may be indicative of proneness for the disease.

Keywords: Alzheimer's disease, high-risk group, memory impairment


How to cite this article:
Halder S, Mahato A. Identifying multiple domain memory impairment in high-risk group for Alzheimer's disorder. J Geriatr Ment Health 2019;6:14-8

How to cite this URL:
Halder S, Mahato A. Identifying multiple domain memory impairment in high-risk group for Alzheimer's disorder. J Geriatr Ment Health [serial online] 2019 [cited 2019 Dec 12];6:14-8. Available from: http://www.jgmh.org/text.asp?2019/6/1/14/264505




  Introduction Top


Long before the actual complaint of memory disturbances, elderly people (later to be diagnosed having Alzheimer's disease [AD]) often report of having memory difficulty and thus are important population for early identification.

There are over 9.9 million new cases of dementia each year worldwide, implying one new case every 3.2 s.[1] Early identification of AD is necessary, as it would help in planning early treatment and appropriate intervention. Research shows that most people currently living with dementia have not received a formal diagnosis. This “treatment gap” is applicable for India as well, with a study suggesting that 90% remain undiagnosed.[1] The figures are staggering and imply for taking suitable measures for an improved quality of life and relatively healthier aging.

Studies show that amnestic and mild cognitive impairment (MCI) group may turn into AD. Individuals with MCI tend to progress to probable AD at a rate of approximately 10%–15% per year.[2] For instance, Mitchell and Shiri-Feshki[3] analyzed 41 high-quality studies (some of which were done on community populations and some in clinical trials) and found that annual conversion rate from MCI to dementia is 5%–10%. Another study[4] found that only 35% of patients diagnosed with MCI at baseline progressed to dementia within the first 3 years of the study. AD is often characterized by a long preclinical period during which deficits in episodic memory are detected. The magnitude of these deficits appears to be quite stable, at least up to 3 years before the diagnosis.[5]

There is increasing evidence that subtle losses in cognitive function may be symptomatic of a transition to early AD. Studies comparing the effects of aging on episodic memory, semantic memory, short-term memory, and priming find that episodic memory is especially impaired in normal aging; some types of short-term memory are also impaired.[6] Along with memory, there is also a decline in other executive functions, processing speed, and reasoning. There is a decline in the ability to form concepts, to abstract and in mental flexibility, inhibiting automatic responses and in inductive reasoning as well.[7]

Although AD is irreversible, the progression from subclinical to clinical phase is not homogenous across population, both in terms of numbers as well as time taken in progression. With this background, the present study aimed to identify older people who are at high risk to develop AD and characterize the deficits in the memory performance of patients reporting memory impairment, without other significant cognitive impairments.


  Subject and Methods Top


It was a cross-sectional study. The sample was drawn during the period of January 2017–May 2018 from different outpatient departments of multispecialty hospitals/mental health clinics in Kolkata. Informed consent was taken from the patients. Consecutive patients of both sexes (n = 57) in the age range of 55–70 years, who studied up to at least Vth grade and presented with complaints of problem in memory, were screened on the Mini–Mental State Examination (MMSE). Patients with a history of substance abuse, depression, psychosis, hearing impairment, and major physical illness were excluded. Patients were identified as high risk due to their memory complaints, scoring in the range of 24–26 on MMSE, but not suggestive of dementia after formal assessment on the Dementia Rating Scale (DRS). The number of patients scoring in the range of 24–26 on the MMSE came to 41. On further assessment on DRS, 11 could meet the criteria for dementia and were further excluded. The remaining patients (n = 30) were identified as the high-risk group and assessed for their memory profile using the PGI Memory Scale (PGIMS).

For normal control group (n = 30), the sample was drawn from community and screened on MMSE (score ≥27). As the control group had no significant impairment, only the PGIMS was administered for assessing the memory profile. Mean scores of the groups were compared using t-test.

Tools administered

  • MMSE:[8] The MMSE is a brief and objective screening test for cognitive impairment that has proven to be valid and reliable across a variety of clinical, epidemiological, and community survey studies. It is a quick and easy to use tool and acceptable to respondents and examiners. It is an effective and widely used method for detecting and quantitatively estimating the severity of cognitive impairment and for documenting cognitive changes over time. By itself, the MMSE was not intended for use as a diagnostic instrument (i.e., for dementia or any other nosological entity)
  • DRS-2:[9] The DRS-2 assesses cognitive functioning on five subscales: attention, initiation–perseveration, construction, conceptualization, and memory. It is very useful in the assessment and progression of dementia of Alzheimer's type. The scale is a 36-task and 32-stimulus card individually administered instrument designed to assess the level of cognitive functioning for individuals with brain dysfunction. It is sensitive at the lower ends of functioning and differentiating levels of deficits
  • PGIMS:[10] It is a part of the PGI battery of brain dysfunction; the PGIMS includes 10 subtests: remote memory (personal information), recent memory (current information), mental balance (3 items of time related), attention and concentration (digit forward and digit backward), delayed recall (1-min delayed recall of a 5-word list), immediate recall (immediate recall of 3 sentences of increasing length), verbal retention for similar pairs (5 pairs of similar words), verbal retention for dissimilar pairs (5 pairs of dissimilar words), visual retention (reproduction of 5 patterns), and recognition (recognizing 10 pictures). The scale is a reliable tool to assess memory functions and standardized in Indian population.



  Results Top


Majority of the participants were above 60 years of age, and males dominated the sample [Table 1].
Table 1: Sociodemographic details and Mini-Mental State Examination and Dementia Rating Scale scores of the participants

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Majority were educated up to 8th standard. Mean age for the high-risk group was 62.1 years and that of the control group was 64.4 years.

On the ten domains of the PGIMS, the high-risk group did not differ from the controls on remote memory, mental balance, attention and concentration, immediate recall, and verbal retention for similar pair tasks. However, controls had significantly better performance on domains of recent memory, delayed recall, visual retention, and recognition [Table 2]. The findings are discussed further in light of existing literature.
Table 2: Comparative performance of the groups on different domains of Post Graduate Institute Memory Scale

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  Discussion Top


The cutoff for age for inclusion in the present study was kept at 55 years, which was based on observation that patients in this particular age reported and consulted for memory problems. Conventionally, people are considered elderly after the age of 60 years; however, research on age-related cognitive decline has reported memory problems in participants <60 years also.[11],[12] While subjective memory complaints can be reported by people as young as 18 years old, there are qualitative differences in these complaints by young and elderly healthy people.[13] Subjective memory complaints have been reported for their usefulness for detecting MCI or early AD.[14] This also supports the basis of grouping patients into high risk in the present study.

Fixing cutoff of MMSE for research could be a complex task, as MMSE scores can be interpreted with slight variation depending on education, range, or severity or single cutoff. The range for MMSE score (24–26) for inclusion into high-risk group in this study was based on available MMSE interpretation[15] that suggests no cognitive impairment above 24. With reference to severity, the mean MMSE score of the high-risk group suggests no impairment in cognitive functions of the participants [Table 1]. Further, the mean score of the high-risk group on DRS did not suggest dementia in the participants.

Despite not showing significant impairment on MMSE and DRS [Table 1], the high-risk group differed significantly with the control group [Table 1] on other memory domains. Domains of impaired memory identified in the high-risk group were recent memory, delayed recall, visual retention, and recognition. The findings are consistent with the literature which suggests that delayed verbal memory is an early indicator of AD. Remote memory is known to be relatively intact in early stages of dementia and consistent with findings of the present study, where high-risk patients did not differ with controls on domain of remote memory and attention and concentration as well.

Relatively poor performance on “delayed recall” by high-risk group in the present study is consistent with literature reporting decline in memory function in 30% of healthy community-dwelling elderly people over 6 years on tasks assessing delayed word list recall.[16] This study also showed deficits on additional tasks of memory and learning, a task of working memory and executive function, and on a verbal (category) fluency task. The memory decline is consistent with the early deterioration characteristic of MCI and preclinical AD. Relatively poor performance of the high-risk group on “retention of dissimilar pairs” is consistent with previous studies[17] which show that normal control and MCI groups differ significantly on phonemic total scores and phonemic switching, and category fluency has been found to be disproportionately impaired compared with phonemic fluency.[18] However, some studies also show that phonemic fluency remained intact for the cognitively normal and preclinical AD groups but showed decline with category fluency in the prevalent AD group.[19]

Although there were no differences in remote memory performance of high-risk and control groups in the present study, previous studies on a large group of MCI patients confirm that in the context of pervasive episodic memory impairment, tests assessing the free recall of verbal material following a delay interval demonstrate greater sensitivity to memory deficits of amnesic MCI participants who developed AD.[20]

Findings of the present study are consistent with study[21] from western part of India in healthy geriatric population revealing deficits in almost all the domains of memory (mental balance, attention and concentration, delayed recall, verbal retention for dissimilar pairs, visual retention and recognition, immediate recall, verbal retention for similar pairs, and visual retention). It also showed that domain of verbal fluency is relatively impaired in healthy geriatric people.

The distinction of AD from non-AD memory impairment may be difficult, especially in mildly affected patients, due to overlapping clinical symptoms between AD and certain non-AD conditions;[22] thus, it is important to look for distinguishing features among the conditions.

High-risk group patients in this study performing at par with controls on long-term memory but poor on working memory is partially consistent with reports of working memory and long term memory getting affected early in AD.[23] The probable reason could be limited number of items assessing remote memory on the measure used. Otherwise, decline of episodic memory is one of the earliest and most prominent features of preclinical AD.[24],[25] It is thought that episodic memory tasks are strong predictors of future AD because the brain areas responsible for episodic memory, such as the medial temporal lobes and the hippocampal formation,[26] are among the first affected.

Several researchers[24],[27],[28] have documented a subtle decline in episodic memory in nondemented older adults prior to the emergence of the obvious cognitive and behavioral and eventually developing AD. Interestingly, in certain cases, this subtle decline in nondemented older adults was evident many years prior to the development of dementia.[29] This is supported by other longitudinal studies[30] too which suggest that individuals who eventually developed probable AD had mild impairment of memory at an evaluation 6 years prior to diagnosis but had little change in memory performance over the next 3 years. They suggest that this long period of stable memory ability in individuals with preclinical AD is followed by a relatively precipitous decline in the period immediately preceding the development of the dementia syndrome.

But again, the ratio of nondemented older adults at risk eventually developing dementia is variable and not all of this population develops dementia. It warrants identifying certain patterns or markers in those at high risk of developing dementia. Studies[31] have found a significant decline in episodic memory and executive functions in individuals with preclinical AD during the period from 3.5 to 1.5 years prior to diagnosis and suggest that an abrupt decline in memory performance could be a better predictor than poor but stable memory abilities for an imminent conversion to dementia.

While executive deficits including attention are prominent in early AD, attention and concentration of the high-risk group in the present study was similar to the control group suggesting stability of the functions at initial stage in the high-risk group.

The discrimination of high-risk group for AD from normal aging is a difficult task in clinical settings, especially when elderly clients may have other physical conditions in priority. It requires more extensive neuropsychological assessment and brain studies. However, screening and assessment of high-risk participants for memory impairment may lead to early diagnosis of dementia. Findings of the study imply that patients aged above 55 years and with subjective memory complaints should be undertaken for detail memory assessment, even if initial screening is inconclusive of dementia or suggests no significant cognitive impairment. A longitudinal component to diagnosis of MCI can be applied, and appropriate therapeutic measures can be designed accordingly.

It is often opined that that consultation with medical experts for complaints relating to cognitive aging is proportionate to the severity of the impairment, and family members may wait until severe medical conditions or behavioral problems manifest.[32] In this scenario, an early detection can help in better treatment planning and decision-making for both the patient and their caregivers.


  Conclusion Top


It can be concluded that an important early indicator of AD is the loss of effective interaction between various neuropsychological domains, and memory impairment plays a significant role in the deterioration of the well-being of the aged population. It calls for the need of early screening, and intervention strategy can be designed to impede disease progression. The present study shows that the high-risk group for AD in the age range of 55–70 years differed significantly with the control group, which performed better on domains of recent memory, delayed recall, verbal retention for dissimilar pair, visual retention, and recognition. These memory domains could be part of standard evaluation when assessing elderly clients with memory problems in initial stage.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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