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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 6  |  Issue : 3  |  Page : 233-237

Attention, memory, and executive functioning in hypoxemic chronic obstructive pulmonary disease patients


1 Clinical Psychologist, St. Xavier's' University, Kolkata, West Bengal, India
2 Department of Psychology, St. Xavier's' University, Kolkata, West Bengal, India
3 Department of Clinical Psychology, Amity University, Kolkata, West Bengal, India

Date of Submission08-Jul-2021
Date of Decision30-Jul-2021
Date of Acceptance01-Aug-2021
Date of Web Publication31-Oct-2022

Correspondence Address:
Dr. Susmita Halder
Bhanumati Road, AA II, Newtown, Kolkata - 700 135, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/aip.aip_85_21

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  Abstract 


Background: Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow obstruction and is one of the leading causes of death globally. The changes in pulmonary functions in COPD are irreversible with devastating consequences. Cognitive functioning in COPD patients is often found impaired and postulated to happen due to hypoxemia, i.e., oxygen deprivation to the brain. An impaired cognitive functioning can have direct impact on functional abilities as well as quality of life of patients and could be a vital treatment goal. The study aimed to explore the attention, memory, and executive functioning in hypoxemic COPD patients in backdrop of dearth of studies from India. Materials and Methods: Using purposive sampling, 30 patients with COPD, having mild-to-moderate level of illness severity, and having minimum illness for duration of 5 years were compared with 30 healthy controls. Participants were assessed for cognitive functioning in the domains of sustained attention, processing and psychomotor speed, working memory, verbal learning, and memory and executive functions using neuropsychological tests, namely, Digit Symbol Substitution Test, Trial Making Test, Verbal N Back Test, Rey's Audio Visual Learning Test, Controlled Oral Word Association Test, Animal Naming Test, Stroop Neuropsychological Test, and Modified Wisconsin Card Sorting Test. Results: Findings suggest significant differences between COPD patients and healthy controls over processing and psychomotor speed, working memory, memory, learning, and executive functioning. Conclusion: In addition to pulmonary distress, COPD patients also have compromised cognitive functions affecting overall daily functioning and quality of life. Understanding the nature of decline in cognitive functions could be vital in improving daily psychosocial functioning of the patients with COPD, and the exploration could help professionals in intervention of specific cognitive functioning.

Keywords: Chronic obstructive pulmonary diseases, cognitive functioning, executive functioning, working memory


How to cite this article:
Samajdar S, Halder S, Mahato AK. Attention, memory, and executive functioning in hypoxemic chronic obstructive pulmonary disease patients. Ann Indian Psychiatry 2022;6:233-7

How to cite this URL:
Samajdar S, Halder S, Mahato AK. Attention, memory, and executive functioning in hypoxemic chronic obstructive pulmonary disease patients. Ann Indian Psychiatry [serial online] 2022 [cited 2022 Dec 4];6:233-7. Available from: https://www.anip.co.in/text.asp?2022/6/3/233/360083




  Introduction Top


Chronic obstructive pulmonary disease (COPD) is categorized as inflammatory lung disease with airflow limitations. COPD results in accelerated decline of lung functioning, which leads to morbidity and mortality. COPD is the third leading cause of death worldwide, and the death rate has an increasing trend every year.[1] COPD is the second most prevalent cause of death after road traffic accidents in India as well.[2] COPD patients experience prolonged respiratory symptoms and incapacity in physical functioning along with several comorbid conditions. The significant symptoms of COPD include severe shortness of breath, coughing, oxygen deprivation, and sputum production, which lead to significant impairment in daily life performance and functioning in activities.[3] Chronic and progressive airway obstruction present in COPD could enhance the adverse hypoxic effect on the brain to an extent that manifests in impaired cognitive functions.

The prevalence rate for cognitive impairment according to validated diagnostic criteria in patients with COPD is reported to be 32.8%.[4] Patients with mild-to-moderate level of COPD have been further diagnosed with cognitive decline and mild cognitive decline, which can be the indication of cognitive impairment and dementia among the patients.[5] Cognitive difficulties have been mainly associated with declination in daily functioning, reduced treatment adherence, and mortality. Pulmonary dysfunction might not always indicate cognitive impairment, but the associated extrapulmonary effects, i.e., systematic inflammation and reduction in physical activities, may lead to cognitive decline in patients with COPD.

Maladaptive lifestyles such as smoking, reduced exercise capacity, depressed mood, and comorbid disorders such as cardiovascular disease and sleep apnea are additional risk factors for aggravation of the condition. These factors might have an adverse impact on cognitive functioning, irrespective of patient's age and education level.[6]

Reducing the symptoms related to disease is the primary focus of treatment of COPD patients; however, intervention strategies now also include providing psychological support as well. Early identification of minimal decrease in cognition is necessary to reduce[7] the risk of severe cognitive impairment and functional decline in COPD patients. Research from the subcontinent on cognitive dysfunctions in COPD, and its connection with overall treatment outcome and daily living functioning, is still in its infancy and needs exploration. Considering the prevailing air quality in metros and major cities of India, it is pertinent to gauge the impact of COPD on not only cognitive functions but also overall functioning and quality of life of the patients. With the above background, the study aimed to explore the attention, memory, and executive functioning in hypoxemic COPD patients in backdrop of dearth of studies from India.


  Materials and Methods Top


Study design and sample

Using purposive sampling, 30 patients of both sexes in the age range of 50–70 years diagnosed with mild-to-moderate level of hypoxemic COPD in accordance to the Global Initiative of Chronic Obstructive Lung Disease were recruited for the study. Minimum illness duration was 5 years or more after diagnosis, and all were educated minimum up to 8th grade. The patient were compared with healthy controls (n = 30) with similar age, sex, and education profile. Any individuals with previous or existing history of psychiatric, other medical, or neurological conditions were excluded from the sample. Five cases dropped out during data collection process, and new participants were recruited following the inclusion and exclusion criteria. Data were collected from the outpatient department of multispecialty hospitals, clinics, and communities of Kolkata. Informed consent was taken from all participants and confidentiality was maintained.

Materials

Following tools were used to assess the attention, memory, and executive functioning of the sample.

Digit Symbol Substitution Test (DSST)[8] is a test of visuomotor coordination, motor persistence, sustained attention, and response speed. The total time and the total number of errors were the parameters for analysis. Indian norms for the test were used.

Trial Making Test (TMT)[9] is a known neuropsychological test of visual attention and task switching. The test can provide information regarding visual search speed, scanning, speed of processing, mental flexibility, as well as executive functioning.

Verbal Working Memory N Back Test[8] was used to assess verbal working memory. The Verbal 1N Back Test requires verbal storage and rehearsal, whereas the 2N Back Version requires manipulation of information. In this test, the total numbers of hits, omissions, and commission were the parameters.

Rey's Auditory Verbal Learning Test (AVLT)[8] assesses the memory and learning capacity of the individual and consists of lists of words in two sections and the teste need to reproduce those.

Controlled Oral Word Association Test[8] assesses phonemic fluency of an individual by generating words based on phonetic similarity of words. The subject is required to produce words beginning with the letters F, A, and S for 1 min. Phonemic fluency is a domain of executive functioning.

Animal Naming Test (ANT)[8] assesses verbal categorical fluency and is the content of the words rather than the phonetic similarity of the words, which is regulated. The subject generates words that belong to a particular semantic category. The ANT requires the subject to produce names of animals for 1 min.

Stroop Neuropsychological Screening Test[10] measures response inhibition and ease with inhibitory control to the habitual response by suppressing along with unusual perceptual demands in the test.

Modified Wisconsin Card Sorting Test (M-WCST)[11] is an adaptation of the Wisconsin Card Sorting Test and widely used neuropsychological test for assessing higher-order cognitive functioning, or executive functioning, that is interlinked with problem-solving, decision-making, and planning.

Procedure

The study was approved by the Departmental Research Committee, AIBHAS, AUK. Patients were contacted from different respiratory clinics and multispecialty hospitals, and healthy controls were from residential areas of Kolkata. Informed consent was taken for their voluntary participation, and they were screened as per inclusion and exclusion criteria and further assessed on the neuropsychological tests. All the scales were scored, and quantitative analysis was done through descriptive statistics. Student's t-test was used to differentiate between the groups (COPD and normal controls). Statistical treatment was conducted through Statistical Package for Social Science software version 17 for Windows (SPSS, Inc. Chicago, Illinois, USA).


  Results Top


The sociodemographic details; illness characteristics of the COPD patients and the cognitive functions of the COPD patients in comparison to normal controls is tabulated in [Table 1], [Table 2] and [Table 3] respectively.
Table 1: Socio-demographic details of the sample

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Table 2: Illness duration and symptom severity of hypoxemic COPD patients

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Table 3: Attention, memory and executive functioning in hypoxemic COPD patients and normal controls

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  Discussion Top


The sociodemographic details [Table 1] suggest no significant difference between COPD patients and normal controls in terms of age of education. COPD patients were predominantly males (60%), but there was no significant difference in frequency of male and female COPD patients in the sample. COPD has been more prevalent in males, but recent studies have reported an increasing prevalence in women.[12] Even though smoking is a big causal factor of COPD, the fact that none of the female COPD patients in the sample were active smokers stresses the etiological role of air pollutants and passive smoking to which they have been exposed causing COPD. It further stresses the need of good air quality considering its long-term impact on cognitive functions.

Mean illness duration of COPD patients was around 15 years with majority having moderate level of illness severity and was an expected finding considering the inclusion criteria [Table 2].

The performance on different neurocognitive tests [Table 3] suggests multifaceted deficits in cognitive functions among the patients with COPD in comparison to normal controls. The participants were assessed on the domains of processing speed and psychomotor speed, attention, working memory, verbal learning and memory, and executive functioning using DSST, TMT, N Back, Rey's AVLT, Controlled Oral Word Association, Stroop neuropsychological screening test, ANT, and M-WCST. While normal controls performed better than COPD patients invariably on almost all domains, statistically not all differences were significant.

COPD patients had significantly lower performance on the DSST, indicating deficits in the domain of processing and psychomotor speed compared to normal controls, which corresponds to slowness in the production of task output in a specific amount of time. The finding is consistent with study,[13] stating statistically low achievement by COPD patients in time reaction tasks due to hypoxemia.

Mean scores of COPD patients on TMT though was higher than normal control, no significant difference was found indicating no significant deficit in domain of attention. Previous studies[14] have suggested patients with mild-to-moderate hypoxia performing poorly on alerting, orienting tasks, and sustained attention.

Working memory as assessed with N Back Test indicates significant deficit in the domain among COPD patients. COPD condition is known to lead into abnormal neuronal activity in the prefrontal-limbic network, including the dorsal prefrontal and orbitofrontal cortices and the parahippocampal gyrus associated with a decrease in working memory, and this consequently may lead to problems with maintaining information processing.[14] Considering the very wide implication of working memory in activities of daily living, this could probably be the gravest impact of COPD on cognitive functions of patients.

In the domain of verbal learning and memory functions assessed with the AVLT, significant differences in the performance of COPD patients were found who performed poorly compared to normal controls. Existing literature suggests that alteration of memory functioning might be the reason of impact of oxygen deprivation and increased systematic inflammation in patients with COPD.[15] Decreased capacity of verbal learning is interlinked with hypoxic insults to the brain along with glia activation.[16] The decline in learning capacity and memory functions of the COPD patients in the present study may be attributed to their illness severity and related oxygen deprivation. This finds support from existing literature suggesting that hypoxia in COPD patients results into relatively focused pattern of impairment in memory functions and tasks requiring attention allocation along with verbal memory and delayed recall impairment.[17] Studies[18] suggest that 48.5% of COPD patients had a specific pattern of cognitive dysfunctions characterized by impairment in verbal and memory tasks, well-preserved visual attention, and diffuse declining of the other functions.

Further, in the domain of executive functions too, COPD patients differed significantly from normal controls. All the parameters of the neuropsychological test were not statistically significant, e.g. on the Controlled Oral Word Association and ANT; however, on the Stroop color word task, COPD patients took significantly more time and made more errors. On modified WCST too, COPD patients could complete lesser correct categories. Existing studies suggest that COPD patients might have depressed cerebral perfusion inclined to decreased oxygen saturation which might have major negative impact over the execution, planning, and problem-solving among patients.[13] The present study findings are consistent with studies that found impairments in planning, problem-solving ability, working memory, response inhibition, abstraction abilities, and deductive thinking among COPD patients.[14],[19]

Patients with hypoxemic COPD tend to perform better on tasks assessing verbal ability and immediate verbal memory, but their performances remained deficient as compared to controls[20] due to functional disability for prolonged disease conditions. It has also been found that the most affected neurocognitive domains are executive functioning which includes the capacity of the patients in sustaining attention for certain time period, situational problem-solving capability, and planning and reasoning for task execution, with minimal deficits in language comprehension and verbal fluency along with significant adverse impact upon domains of memory.[21]

The study data were further analyzed to see if COPD patients with different illness duration differed on their level of cognitive functions. A comparison of within-group COPD patients divided into patients with illness duration of up to 10 years and patients with illness duration of more than 10 years was done. Findings reveal no significant differences within the subgroups on all test performances, except N Back 2, assessing working memory (t = 2.133, P = 0.02). This suggests particular vulnerability of working memory functions in COPD patients for further deterioration with longer illness duration. A plausible explanation of no significant difference in COPD within group could be that all patients in the study had a minimum illness duration of 5 years and were chronic in nature by default. Cognitive dysfunction in COPD patient is not only related to the continuation of symptoms over years but also the period of inflammation in shorter period of time, which might affect cognitive functions. A key mechanism proposed for cognitive dysfunction in COPD is neuronal damage mediated through hypoxia, but it has also been suggested that oxygen-dependent enzymes which are important in the synthesis of neurotransmitters affect the cognitive functions every time the exacerbation takes place.

Overall, it could be inferred that the disease condition has had an impact on cognitive functioning of COPD patients. As deficits in cognitive flexibility and response inhibition are related to flexible thought process, it may hamper attempts by COPD patients to adapt healthy lifestyle, e.g. smoking cessation, and become physically active.[22] Thus, these deficits demand comprehensive neuropsychological and psychosocial interventions for betterment of overall disease condition.


  Conclusion Top


COPD is a disabling disease with wide-ranging detrimental effects and global deficiency in cognitive functioning in terms of processing and psychomotor speed, working memory, verbal learning, and memory and executive functioning. The deficits were evident in patients with illness duration of even 5 years and worsening in domain of working memory with longer illness duration. The study findings also reveal an increasing trend in the prevalence of COPD in women. The study findings have wide implications in terms of early intervention for patients with COPD, which either way causes significant limitations in functioning of the patients and causes psychological distress. The cognitive deficits secondary to COPD could accelerate progression of cognitive impairment in elderly population. Future research can focus upon the identified deficit areas of the neurocognitive domains for early intervention and decelerate the progression toward severe cognitive impairment in COPD patients in later age.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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