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Smith.

Research Article
WORLD JOURNAL OF PHARMACEUTICAL
World Journal of Pharmaceutical and Medical Research
ISSN
2455-3301
AND MEDICAL RESEARCH

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MEMORY IMPAIRMENTS IN CHRONIC FATIGUE SYNDROME PATIENTSAndrew P. Smith*
PhD School of Psychology, Cardiff University.
*Corresponding Author: Prof. Andrew P. Smith
PhD School of Psychology, Cardiff University.

Article Received on 12/04/2022

Article Revised on 01/05/2022

Article Accepted on 22/05/2022

ABSTRACT
Background: Chronic Fatigue Syndrome (CFS) patients often report memory problems. Prior research has
produced conflicting results on this topic. Episodic memory impairments appear to be robust, but tasks assessing
other aspects of memory (e.g., working and semantic memory) show slower speed but no decrease in accuracy.
This study examined whether the memory problems of CFS patients reflect slower responses. Methods: CFS
patients were recruited from a specialist clinic. Sixty-seven patients carried out tasks measuring immediate recall,delayed recognition memory, logical reasoning and semantic processing. The control group were 126 healthy
volunteers recruited from the general population. Results: The CFS patients recalled fewer words and had poorer
delayed recognition. The other tasks showed slower speed but no effect on accuracy. Conclusions: CFS patients
have poorer immediate recall and delayed recognition memory. The delayed recognition memory probably
reflected the poorer immediate recall. Slower responding was present in three of the tasks, and it is possible that
this also accounted for the reduced immediate recall.
KEYWORDS: CFS, Chronic Fatigue Syndrome, Memory, Free Recall, Recognition Memory, Working Memory,
Semantic Memory, Speed and Accuracy.
have to exert greater effort to process auditory
information as effectively as demographically similar
healthy adults.[28]INTRODUCTION
Chronic Fatigue Syndrome (CFS) is mainly characterisedby persistent fatigue, but this can be accompanied bycognitive problems such as reports of impairment ofmemory. Some research has suggested that objective
measurement of memory does not confirm the problems
reported by the patients.[1,2] This lack of significant
memory differences between CFS patients and controls
has been confirmed in some of the research.[3-13]
However, other studies found memory impairments in
CFS patients.[14-30] These memory impairments havebeen interpreted in terms of impaired concentration, lesseffort and speed of processing.[14,15]

Another selective effect obtained in research on memory
and CFS has been that CFS patients have slower
information processing speed but show no differences inaccuracy.[25] This view has been confirmed in studies of
CFS and selective attention in choice reaction time tasks,
with the CFS group having slower responses but notdiffering in aspects of selective attention.[31]Research from our laboratory has shown that CFS
patients have impairments in immediate free recall anddelayed recognition memory of a list of words. [16-18]
Other tasks involving working memory and semantic
processing have shown that these are performed more
slowly by CFS patients but that there is no difference inaccuracy. The aim of the present analyses was toreplicate these effects on recall and recognition and to
examine whether effects on other outcomes are restrictedto speed rather than accuracy.

Other research has suggested that only certain types oftasks are impaired in CFS patients. For example,
impairments in CFS have been shown to be restricted tomore demanding memory tasks.[23] Visual memory tasks
also appear to be more likely to be impaired. [27] Research
has also examined the type of processing that may be
involved. For example, one study suggested that
impairments reflected poorer initial storage rather thanretrieval.[26] Other studies have combined memory tasks
with brain scanning, and findings showed that
individuals with CFS are able to process challenging
auditory information as accurately as controls but utilise
more extensive regions of the network associated withthe verbal WM system. Individuals with CFS appear towww.wjpmr.com│

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MATERIALS AND METHODS
The study was carried out with the informed consent of
the volunteers and the approval of the local regional
ethical committee.

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World Journal of Pharmaceutical and Medical ResearchParticipants
Sixty-seven Chronic Fatigue Syndrome patients attended
the Health Psychology Research Unit for testing. There
were 20 males and 47 females whose ages ranged from17 to 63 in the case of males with a mean age of 39.65,
and 17 and 73 in the case of females, with a mean age of
43.49. 59.1% of the Chronic Fatigue patients were
married, 33.3% were single, 6.1% were divorcees, and1.5% were widowed. One hundred and twenty-six
members of the general population were recruited to takepart in the study as controls for a Chronic Fatigue
sample. They were recruited from an advertisement in
the local press and selected to participate on the basis ofage and occupational status. Of the 126 general
population participants, there were 43 males and 83
females. The males ranged in age from 21 to 66 years
with a mean age of 39.14 (S.D.=13.53), and the females
from 21 to 79 years with a mean age of 40.48(S.D.=13.02). 50.8% of the general population
participants were married, 32.5% were single, 15.9%
were divorcees, and 0.8% were widowed. The patientsand controls did not differ significantly in terms ofgender, age, occupational status, or pre-morbid
intelligence (measured using the National Adult ReadingTest). Details of the reported symptoms and psychosocial
characteristics of the sample are given in an earlier
article.[31]RESULTSFree recall task
Table 1 shows the results from the free recall task.
Table 1: Results from the free recall task.
Number recalledmsdControls
7.47
1.99
Patients
6.75
2.13
Number correctmsdControls
6.89
2.06
Patients
6.27
2.02
Number incorrectmsdControls
0.59
0.81
Patients
0.48
0.17
Three Wilcoxon tests were performed to test differences
between the Control and Chronic Fatigue Syndromegroups for number recalled, number correct, and number
incorrect. The results showed that for number recalled,there were significant differences between groups(X2=4.84; df=1; p<0.05), for number correct, there werealso significant differences between groups (X2=3.87;
df=1; p<0.05), but for number incorrect there were no
significant differences between groups (X2=0.49; df=1;
p>0.05). The results indicate that Patients recalled fewerwords than the Controls and that they recalled fewerwords correctly but recalled similar numbers of incorrect
words.

Memory tasks
Free recall task: The participants were shown a list of
20 words presented at the rate of one every 2 seconds. At
the end of the list, they had 2 minutes to write down (inany order) as many of the words as possible.

Logical reasoning test
Table 2 shows the results from the logical reasoning task.
Table 2: Results from the logical reasoning task.
Number completed% correct
msd
msd
Controls 36.35 12.6
78.11 19.46
Patients 32.37 11.31
74.58 20.2

Logical reasoning task: Participants were shownstatements about the order of the letters A and B
followed by the letters AB or BA (e.g. A follows B BA).
They had to read the statement and decide whether it wasa true description of the order of the letters. If it was, thevolunteer pressed the T key on the keyboard, if it wasn't,
they pressed the F key. The sentences ranged in syntactic
complexity from simple active to passive negative (e.g.
A is not followed by B). The volunteers completed as
many as possible in 3 minutes.

A Wilcoxon test examining differences between theControl and the Chronic Fatigue Syndrome groups forthe number of trials completed showed a significant
difference between the groups (X2=4.28; df=1; p<0.05).
A Wilcoxon test between Control and Chronic Fatigue
groups for per cent correct showed no significant
differences between the groups (X2=1.66; df=1; p>0.05).
These results indicate that the Chronic Fatigue groupcompleted fewer trials but had similar accuracy rates to
the Control group.

Semantic processing task: This task measures the speedof retrieval of information from general knowledge.
Participants were shown a sentence and had to decide
whether it was true (e.g., canaries have wings) or false(e.g. dogs have wings). The number completed in 3
minutes was recorded.

Semantic processing test
Table 3 shows the results from the semantic processing
task.
Table 3: Results from the semantic processing task.
Number done
% correct
msd
msd
Controls
99.1
24.71
95.06
2.81
Patients
84.8
24.46
95.68
3.19

Delayed recognition memory task: At the end of the test
session, the participants were shown 40 words which
consisted of the 20 words shown at the start plus 20
distractors. The participant had to decide whether eachword had been shown in the original list or not.

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A Wilcoxon test which examined differences between
Patients and Controls for the number done showedsignificant differences between groups (X2=13.13; df=1;
p<0.01). A Wilcoxon test for per cent correct did notshow differences between groups, however (X2=2.35;
df=1; p>0.05), illustrating that Patients completed fewer
trials than controls but obtained similar accuracy rates.

could even reflect the poorer free recall, where slower
writing speed may lead to an impaired recall.
DISCUSSION
The results presented here confirm the slower
performance of memory tasks by CFS patients. The
slower responses were observed in the delayed
recognition memory task, logical reasoning task andsemantic processing task. Tasks which demonstrated
significant effects for speed rarely showed significant
effects for accuracy. The exceptions to this were theimmediate free recall and delayed recognition memorytask. The reduced recognition memory accuracy
plausibly reflected the lower levels of immediate recall.
The immediate free recall task involved writing down thewords, and it is likely that the CFS patients took longer
to do this. The longer writing time may then have had anegative impact on the subsequent recall of more words.

Delayed recognition memory test
Table 4 shows the accuracy results of the delayed
recognition memory test. A Wilcoxon test examineddifferences between the Chronic Fatigue Syndrome
patients and the Control group and for ‘Hits’ showedsignificant differences between groups (X2=5.21; df=1;
p<0.05). For 'False Alarms', a Wilcoxon test showed nosignificant differences between groups (X2=3.11; df=1;
p>0.05). These results indicate that the Chronic Fatigue
patients had fewer 'Hits' (identified fewer correct words)
but made similar numbers of 'False Alarms' (make false
identification of incorrect words). The fewer hitsplausibly reflect the smaller number of words correctly
recalled immediately after the presentation.

A recent study[31] investigated whether CFS patients had
impaired selective attention in choice reaction time tasks.
The results showed no difference in selective attention
between CFS patients and controls, although the speed of
response of the CFS patients was slower than that ofcontrols. It should be pointed out that the varying resultsin studies of memory in CFS patients could reflectvariation in correlated attributes of CFS. The most likely
factors are depression and sleep problems, and thesehave been shown to be important in the cognitive
problems of CFS patients.[21,32] Further research is neededto address this issue, and it will also be important to use
other memory tasks and measures of both speed andaccuracy to determine whether explanations based on
slower responses will generalise to other aspects ofmemory.

Table 4: Results from the delayed recognition
memory task.
Hits
m
sd
Controls
15.71 2.68
Patients
14.35 3.72
False Alarmsmsd
Controls
4.91
2.83
Patients
4.09
2.72
Reaction times were also recorded in this task, and theseresults are shown in Table 5.
Table 5: Reaction time (msec) results from thedelayed recognition memory task.
Hits
m
sd
Controls
993
249
Patients
1422
958
False Alarmsmsd
Controls
1350
563
Patients
1857
1203

CONCLUSIONS
The results of the present study confirm that CFS
patients have impaired performance on recall andrecognition memory tasks, logical reasoning andsemantic processing. The slower speed of performing thetasks was apparent, and it is suggested that this may leadto impaired recall due to the longer time taken to write
down the words.
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Wilcoxon tests showed significant differences between
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