Association between sleep characteristics and mild cognitive impairment in elderly people
We compared the sleep quality indices between patients with mild cognitive impairment (MCI) and normal elderly subjects and analyzed the effects of sleep characteristics on cognitive functions. Cases of MCI patients (320 persons, MCI group) and 630 normal elderly with matched age, gender, and lev...
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Інститут фізіології ім. О.О. Богомольця НАН України
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nasplib_isofts_kiev_ua-123456789-1482522025-02-09T10:15:02Z Association between sleep characteristics and mild cognitive impairment in elderly people Зв’язки між характеристиками процесу сну та помірними порушеннями когнітивних функцій у людей похилого віку An, C. Yu, L. Wang, L. Jin, G. Song, M. Zhu, Q. Jia, H. Liu, K. Wang, M. Wang, X. We compared the sleep quality indices between patients with mild cognitive impairment (MCI) and normal elderly subjects and analyzed the effects of sleep characteristics on cognitive functions. Cases of MCI patients (320 persons, MCI group) and 630 normal elderly with matched age, gender, and level of education (control group) were enrolled in this study. The Pittsburgh Sleep Quality Index (PSQI) was used to assess the sleep characteristics. The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to assess cognitive function. There were 110 (34.3%) and 170 (27%) cases with sleep disorders in the MCI and control groups, respectively (P < 0.01). There was a significant difference of total PQSI scores between the two groups, and the scores of sleep duration (factor III) and habitual sleep efficiency (factor IV) in the MCI group were significantly lower than those in the control group. Total PQSI scores negatively correlated with MoCA scores and MMSE scores. MoCA scores negatively correlated with scores of the sleep latency (factor II), sleep duration (factor III), and habitual sleep efficiency (factor IV), while MMSE scores negatively correlated with scores of factor III and factor IV. The scores of attention and calculation, reading and language understanding, and visuospatial function (MMSE), and also of visuospatial/executive function, attention, and clock-drawing test (MoCA) in MCI patients without sleep disorders were significantly higher than those in MCI patients with such disorders. The incidence of sleep disorders is higher in patients with MCI, compared with normal elderly. Effects of sleep disorders on cognitive functions are mainly reflected in the state of attention, and visuospatial/executive function. Ми порівнювали показники якості сну у пацієнтів з помірними когнітивними порушеннями (MCI) та літніх людей без таких розладів і аналізували впливи характеристик процесу сну на когнітивні функції. У дослідженні брали участь 320 пацієнтів групи MCI та 630 здорових літніх людей контрольної групи, в яких співпадали вік, стать та рівень освіти. Для оцінки якості сну використовували Пітсбургський індекс якості сну PSQI, а для оцінки статусу когнітивної сфери – системи MMSE та MoCA. У групах МСI та контролю було 110 (34.3 %) та 170 (27 %) випадків розладів сну (P < 0.01). Сумарні значення оцінок PSQI демонстрували вірогідні міжгрупові відмінності; оцінки тривалості сну (фактор III) та звичайної ефективності сну (фактор IV) у групі MCI були вірогідно нижчими, ніж у контрольній групі. Загальні оцінки PSQI негативно корелювали з оцінками за шкалами MoCA та MMSE. Оцінки за MoCA негативно корелювали зі значеннями латентного періоду сну (фактор II), тривалості сну (фактор III) та звичайної ефективності сну (фактор IV), тоді як оцінки за MMSE знаходились у негативній кореляції з бальними оцінками факторів III та IV. Бальні оцінки за шкалами уваги, кількісних розрахунків, розуміння читання й мовлення та просторово-зорової функції за MMSE, а також просторово-зорової/виконавчої функції, уваги та тесту з малювання годинника за MoCA у пацієнтів групи MCI без розладів сну були істотно більшими, ніж відповідні значення у MCI-пацієнтів з такими розладами. Таким чином, частота розладів сну у пацієнтів із помірними розладами когнітивної сфери є вищою, ніж така у здорових літніх осіб. Впливи розладів сну на когнітивні функції в основному відображуються в розладах уваги та просторово-зорової/виконавчої функції. This work was supported by the Science and Technology Support Program of Hebei Province (No. 09276103D). 2014 Article Association between sleep characteristics and mild cognitive impairment in elderly people / C. An, L. Yu, L. Wang, G. Jin, M. Song, Q. Zhu, H. Jia, K. Liu, M. Wang, X. Wang // Нейрофизиология. — 2014. — Т. 46, № 1. — С. 94-100. — Бібліогр.: 39 назв. — англ. 0028-2561 https://nasplib.isofts.kiev.ua/handle/123456789/148252 616.89–008.457–009.836 en Нейрофизиология application/pdf Інститут фізіології ім. О.О. Богомольця НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
We compared the sleep quality indices between patients with mild cognitive impairment
(MCI) and normal elderly subjects and analyzed the effects of sleep characteristics on
cognitive functions. Cases of MCI patients (320 persons, MCI group) and 630 normal elderly
with matched age, gender, and level of education (control group) were enrolled in this study.
The Pittsburgh Sleep Quality Index (PSQI) was used to assess the sleep characteristics. The
Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were
used to assess cognitive function. There were 110 (34.3%) and 170 (27%) cases with sleep
disorders in the MCI and control groups, respectively (P < 0.01). There was a significant
difference of total PQSI scores between the two groups, and the scores of sleep duration
(factor III) and habitual sleep efficiency (factor IV) in the MCI group were significantly
lower than those in the control group. Total PQSI scores negatively correlated with MoCA
scores and MMSE scores. MoCA scores negatively correlated with scores of the sleep latency
(factor II), sleep duration (factor III), and habitual sleep efficiency (factor IV), while MMSE
scores negatively correlated with scores of factor III and factor IV. The scores of attention
and calculation, reading and language understanding, and visuospatial function (MMSE), and
also of visuospatial/executive function, attention, and clock-drawing test (MoCA) in MCI
patients without sleep disorders were significantly higher than those in MCI patients with
such disorders. The incidence of sleep disorders is higher in patients with MCI, compared
with normal elderly. Effects of sleep disorders on cognitive functions are mainly reflected in
the state of attention, and visuospatial/executive function. |
| format |
Article |
| author |
An, C. Yu, L. Wang, L. Jin, G. Song, M. Zhu, Q. Jia, H. Liu, K. Wang, M. Wang, X. |
| spellingShingle |
An, C. Yu, L. Wang, L. Jin, G. Song, M. Zhu, Q. Jia, H. Liu, K. Wang, M. Wang, X. Association between sleep characteristics and mild cognitive impairment in elderly people Нейрофизиология |
| author_facet |
An, C. Yu, L. Wang, L. Jin, G. Song, M. Zhu, Q. Jia, H. Liu, K. Wang, M. Wang, X. |
| author_sort |
An, C. |
| title |
Association between sleep characteristics and mild cognitive impairment in elderly people |
| title_short |
Association between sleep characteristics and mild cognitive impairment in elderly people |
| title_full |
Association between sleep characteristics and mild cognitive impairment in elderly people |
| title_fullStr |
Association between sleep characteristics and mild cognitive impairment in elderly people |
| title_full_unstemmed |
Association between sleep characteristics and mild cognitive impairment in elderly people |
| title_sort |
association between sleep characteristics and mild cognitive impairment in elderly people |
| publisher |
Інститут фізіології ім. О.О. Богомольця НАН України |
| publishDate |
2014 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/148252 |
| citation_txt |
Association between sleep characteristics and mild cognitive impairment in elderly people / C. An, L. Yu, L. Wang, G. Jin, M. Song, Q. Zhu, H. Jia, K. Liu, M. Wang, X. Wang // Нейрофизиология. — 2014. — Т. 46, № 1. — С. 94-100. — Бібліогр.: 39 назв. — англ. |
| series |
Нейрофизиология |
| work_keys_str_mv |
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NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 194
UDC 616.89–008.457–009.836
C. AN,1,2 L. YU,1,2 L. WANG,1,2 G. JIN,1,2 M. SONG,1,2 Q. ZHU,1,2 H. JIA,1,2 K. LIU,1,2 M. WANG,1,3 and X. WANG1,2
ASSOCIATION BETWEEN SLEEP CHARACTERISTICS AND MILD COGNITIVE
IMPAIRMENT IN ELDERLY PEOPLE
Received March 29, 2013.
We compared the sleep quality indices between patients with mild cognitive impairment
(MCI) and normal elderly subjects and analyzed the effects of sleep characteristics on
cognitive functions. Cases of MCI patients (320 persons, MCI group) and 630 normal elderly
with matched age, gender, and level of education (control group) were enrolled in this study.
The Pittsburgh Sleep Quality Index (PSQI) was used to assess the sleep characteristics. The
Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were
used to assess cognitive function. There were 110 (34.3%) and 170 (27%) cases with sleep
disorders in the MCI and control groups, respectively (P < 0.01). There was a significant
difference of total PQSI scores between the two groups, and the scores of sleep duration
(factor III) and habitual sleep efficiency (factor IV) in the MCI group were significantly
lower than those in the control group. Total PQSI scores negatively correlated with MoCA
scores and MMSE scores. MoCA scores negatively correlated with scores of the sleep latency
(factor II), sleep duration (factor III), and habitual sleep efficiency (factor IV), while MMSE
scores negatively correlated with scores of factor III and factor IV. The scores of attention
and calculation, reading and language understanding, and visuospatial function (MMSE), and
also of visuospatial/executive function, attention, and clock-drawing test (MoCA) in MCI
patients without sleep disorders were significantly higher than those in MCI patients with
such disorders. The incidence of sleep disorders is higher in patients with MCI, compared
with normal elderly. Effects of sleep disorders on cognitive functions are mainly reflected in
the state of attention, and visuospatial/executive function.
Keywords: sleep, mild cognitive impairment, cognitive functions, Montreal Cognitive
Assessment, Mini-Mental State Examination, Pittsburgh Sleep Quality Index
1First Hospital of the Hebei Medical University, Shijiazhuang, China;
2Mental Health Institute of the Hebei Medical University, Shijiazhuang, China;
3Hebei Brain Ageing and Cognitive Neuroscience Laboratory, Shijiazhuang,
China
Corresponding should be addressed to:
M. Wang (e-mail: mingweiwangcn@yeah.net)
or to X. Wang (e-mail: xueyiwanga@yeah.net_
INTRODUCTION
With increase in age and appearance of age-related
problems, the incidence of sleep disorders increases [1,
2]. Mild cognitive impairment (MCI) is a mild memory
or cognitive dysfunction, which can be diagnosed
but does not dramatically affect living abilities. It
is a clinical status between normal aging and early
dementia [3]; at the same time, it is considered an
ultra-early stage of Alzheimer’s disease (AD), with
the risk of progressing to clear, clinically manifested
AD. In recent years, MCI has attracted more and more
attention. Researchers have found that sleep disorders
are indicative of elderly cognitive impairment [4], and
the cognitive decline in normal elderly is significantly
associated with sleep disorders [5]. The sleep quality
positively correlates with psychological test scores.
The worse the sleep quality, the worse the test scores.
Lack of sleep can lead to decline of rapid response
ability and to impairment of executive functions [6,
7]. Positron emission tomography (PET) showed that
there are metabolic declines in cerebral areas related
to attention, information processing, and executive
function in individuals with deprived sleep [8].
Functional magnetic resonance imaging (fMRI) showed
that the state of cortical networks is associated with
sustained attention, and sleep deprivation will disturb
the function of these networks [9]. Sleep impairment
affects visuospatial [10], auditory [11], tactile [12],
and olfactory perception [13]. Sleep disorders can
be considered a concomitant symptom of cognitive
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 95
ASSOCIATION BETWEEN SLEEP CHARACTERISTICS AND MILD COGNITIVE IMPAIRMENT
impairment. At the same time, decreased sleep quality
can further aggravate cognitive impairment.
In our study, the sleep quality in MCI patients was
assessed. The objective was to find an association
between cognitive impairment and sleep disorders.
METHODS
General data. Following the cluster sampling method,
a general questionnaire survey and cognitive function
assessment were conducted on 1605 elderly (≥ 60 years
old) in six communities in Shijiazhuang, Tangshan,
and Handan in Hebei, China, from December 2009
to December 2010. The examined groups included
320 MCI patients (MCI group) and 630 normal elderly
with matched age, gender, and level of education.
In the MCI group, the inclusion criteria were
as follows: (i) Memory impairment was the chief
complaint (confirmed by relatives or insiders);
objective examination showed memory impairment
inconsistent with age and education level, with normal
overall cognitive function and the ability to perform
the activities of daily living; the patients did not meet
the diagnostic criteria for dementia [14]. (ii) The ages
were ≥ 60 years. (iii) Patients could cooperate with the
cognitive function test.
The exclusion criteria were as follows: (i) Patients
could not cooperate with the cognitive function test
due to aphasia, deafness, blindness, color blindness,
or other physical deficiencies. (ii) Patients had
neurological diseases causing clear brain dysfunctions,
including acute stroke and Parkinson’s disease.
(iii) Patients had severe depression, schizophrenia,
phrenitis, and clouding of consciousness, which
impacted the cognitive function assessment. (iv)
Patients had serious physical illnesses affecting sleep.
There were 146 men and 174 women, with a mean age
of 70±6 years (mean ± s. d.) and average 6±4 years of
education.
In the control group, the inclusion criteria were as
follows: (i) The ages were not ≥ 60 years. (ii) There
was no chief complaint of cognitive dysfunction. (iii)
According to the education level, the scores of Mini-
Mental State Examination (MMSE) were higher than
the delimitation, and the scores of Montreal Cognitive
Assessment (MoCA) were not less than 26, with the
scores of activity of daily living (ADL) less than
26. (iv) Subjects could cooperate with the cognitive
function test. Exclusion criteria were the same as
those in the MCI group. There were 302 men and
328 women, with a mean age of 70 ± 6 years and
average 6 ± 4 years of education.
There were no significant differences in age
(F = 2.07, P = 0.35), gender (F = 4.39, P = 0.11),
and average level of education (F = 0.37, P = 0.83)
between the two groups.
Assessment of the cognitive function. All scale
assessments were performed by trained psychiatrists
(after training, the consistency test showed a Kappa of
0.83). The MoCA and MMSE were used for assessment
of the state of the cognitive sphere. The items of
MoCA included visuospatial function, memory,
language fluency, and abstract thinking, with a total
of 30 scores. For subjects with less than 12 years of
education, one score was added to the test result to
correct the bias of the education level. Higher scores
represented better cognitive function. The delimitation
score was 26, and scores less than 26 were considered
indicative of cognitive impairment [15].
The MMSE was commonly used in senile dementia
screening, and its items included orientation, memory,
and attention, with a total of 30 scores. It was more
suitable for patients with moderate to severe dementia,
and the sensitivity and specificity in distinguishing
normal elderly from dementia patients was 80-90%.
Estimates of scores < 27 (junior high school and
above), < 24 (primary school), and < 21 (illiterate)
represented cognitive function decline [16]. In the
MCI group, the MoCA scores were less than 26, and
the MMSE scores were higher than the delimitation
according to different education levels.
Assessment of sleep quality. The sleep quality
(overall sleep quality in the past one month) of subjects
was assessed using the Pittsburgh Sleep Quality Index
(PSQI). The PSQI consisted of 19 questions (e.g.,
during the past two weeks, how long had it usually
taken the subject to fall asleep each night) and
7 subscales. Among the latter, there are subjective
sleep quality (factor I), sleep latency (factor II), sleep
duration (factor III), habitual sleep efficiency (factor
IV), sleep disturbances (factor V), use of medication
(factor VI), and daytime dysfunction (factor VII).
Each factor was graded from 0 to 3. The total PSQI
scores represented the sum of the seven subscales and
ranged from 0 to 21. The PSQI did not ask about mood
symptoms. In general, scores ≥ 5 represented clear
sleep problems [17, 18].
Statistical analysis. Original data were coded and
managed by an independent database established by
the Institute of Basic Medical Sciences and Institute
of Clinical Medicine in the China Academy of
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 196
C. AN, L. YU, L. WANG, et al.
Traditional Chinese Medicine. All data were entered
by professional personnel at a double-entry mode to
ensure correctness. After examination, verification,
modification, and submission, SPSS 17.0 statistical
software was used for statistical analysis. An
independent sample t-test was conducted to analyze
the differences of total PSQI scores and individual
factor scores between the MCI and control groups.
Pearson’s correlation coefficient was used for analysis
of MoCA, MMSE, and PSQI scores in all enrolled
subjects.
RESULTS
Comparisons of the incidence of sleep disorders
and PQSI scores. There were 110 (34.3%) and 170
(27%) cases with clear sleep disorders in the MCI
and control groups, respectively, with a significant
difference between them (F = 7.35, P = 0.007). Total
PQSI scores and individual factor scores in the two
groups are shown in Table 1. There was significant
difference of total PQSI scores between two groups
(F = 4.21, P = 0.04). The scores of sleep duration
(factor III) and habitual sleep efficiency (factor IV)
in the MCI group were significantly lower than those
in the control group (F = 6.90, P = 0.00 and F = 7.51,
P = 0.00, respectively).
Correlations of PQSI scores with MoCA and
MMSE scores. Correlations of total PQSI scores
and individual factor scores with MoCA scores and
MMSE scores are shown in Table 2. Total PQSI
scores negatively correlated with MoCA scores and
MMSE scores, respectively (r = –0.12 and r = –0.09,
respectively). The MoCA scores negatively correlated
with scores of the sleep latency (factor II), sleep
duration (factor III), and habitual sleep efficiency
(factor IV); (r = –0.08, P = 0.01; r = –0.09, P = 0.00,
and r = –0.14, P = 0.00, respectively). The MMSE
scores were negatively correlated with scores of factor
III and factor IV (r = –0.09, P = 0.00 and r = –0.12,
P = 0.00, respectively).
General manifestations in MCI patients with and
without sleep disorders. As shown in Table 3, there
was no significant difference between the frequencies
of cases of angina, hypertension, cerebral infarction,
Table 1. Total PQSI and individual factor estimates in MCI and control groups (scores, M ± s.d.)
Таблиця 1. Сумарні оцінки та оцінки індивідуальних акторів за PQSI в групах MCI та контролю (бали, M ± s.d.).
Group n Total Factor I Factor II Factor III Factor IV Factor V Factor VI Factor VII
MCI 320 6.11±4.29 0.90±0.70 1.20±1.16 0.98±0.98 0.81±1.06 1.13±0.71 0.25±0.07 0.21±0.05
Control 630 5.46±3.94 0.94±0.76 1.29±1.21 1.14±1.06 1.04±1.18 1.18±0.87 0.28±0.07 0.25±0.06
F 4.21 0.37 2.79 6.90 7.51 2.64 1.74 3.80
P 0.04 0.54 0.09 0.00 0.00 0.10 0.18 0.05
Table 2. Correlations of the PQSI estimates with MoCA and MMSE scores
Таблиця 2. Кореляції оцінок за PQSI з бальними оцінками за MoCA та MMSE.
PQSI scores MoCA MMSE
r P r P
Total –0.12 0.00 –0.09 0.00
Factor I –0.03 0.35 –0.02 0.42
Factor II –0.08 0.01 –0.05 0.09
Factor III –0.09 0.00 –0.09 0.00
Factor IV –0.14 0.00 –0.12 0.00
Factor V –0.01 0.74 0.00 0.97
Factor VI –0.06 0.03 –0.06 0.07
Factor VII –0.07 0.02 –0.05 0.11
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 97
ASSOCIATION BETWEEN SLEEP CHARACTERISTICS AND MILD COGNITIVE IMPAIRMENT
Table 3. General pathological manifestations in MCI patients with and without sleep disorders
Таблиця 3. Загальні патологічні прояви у пацієнтів групи MCI з розладами сну та без них.
Manifestation Without sleep disorders (n=210) With sleep disorders (n=110) F P
Angina 19 (9%) 16 (15%) 4.39 0.11
Hypertension 101 (48%) 65 (59%) 5.23 0.07
Cerebral infarction 19 (9%) 13 (12%) 1.94 0.38
Cerebral hemorrhage 6 (3%) 8 (7%) 3.40 0.18
TIA 6 (3%) 8 (7%) 3.40 0.18
Diabetes 31 (15%) 20 (18%) 2.07 0.35
Presbyopia 166 (79%) 91 (83%) 4.81 0.09
Peptic ulcer 6 (3%) 3 (3%) 0.37 0.83
Footnote: Numbers of cases and normalized numbers (%, in parentheses) are shown.
Table 4. Comparison of MMSE estimates between MCI patients with and without sleep disorders
Таблиця 4. Порівняння оцінок за MMSE у пацієнтів групи MCI з розладами сну та без них.
MMSE scores Without sleep disorders (n = 210) With sleep disorders (n = 110) t P
Total 26.39±2.40 26.01±2.54 1.79 0.07
Time orientation 4.66±0.59 4.63±0.69 0.42 0.67
Location orientation 4.92±0.28 4.91±0.34 0.55 0.58
Immediate recall 2.84±0.43 2.86±0.38 –0.38 0.70
Attention and calculation 3.93±1.17 3.69±1.27 2.18 0.03
Delayed recall 2.26±0.81 2.30±0.73 –0.53 0.59
Naming 2.00±0.00 1.99±0.07 1.00 0.32
Recapitulation 0.67±0.47 0.66±0.47 0.35 0.72
Language understanding 2.94±0.25 2.92±0.32 0.85 0.39
Reading and language
understanding
0.92±0.28 0.85±0.36 2.32 0.02
Writing 0.53±0.50 0.54±0.50 –0.17 0.86
Visuospatial function 0.73±0.44 0.64±0.48 2.31 0.02
Table 5. Comparison of MoCA estimates between MCI patients with and without sleep disorders
Таблиця 5. Порівняння оцінок за MoCA у пацієнтів групи MCI з розладами сну та без них.
MoCA scores Without sleep disorders (n = 210) With sleep disorders (n = 110) t P
Total 21.35±3.28 20.44±3.57 3.06 0.00
Visuospatial and executive function 2.79±1.26 2.43±1.29 3.23 0.00
Naming 2.79±0.47 2.71±0.51 1.71 0.09
Attention 4.99±1.02 4.74±1.14 2.61 0.00
Language 1.88±1.75 1.83±0.70 0.80 0.42
Abstract thinking 0.76±0.77 0.72±0.74 0.52 0.60
Delayed recall 1.68±1.33 1.58±1.33 0.84 0.40
Orientation 5.56±0.66 5.50±0.70 0.89 0.37
Clock-drawing test 2.29±0.90 2.08±0.94 2.50 0.01
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C. AN, L. YU, L. WANG, et al.
cerebral hemorrhage, transient ischemia attack (TIA),
diabetes, presbyopia, and peptic ulcer between MCI
patients with and without sleep disorders. The age and
years of education in MCI patients with sleep disorders
matched those in MCI patients without sleep disorders.
Comparison of the MMSE scores between
MCI patients with and without sleep disorders.
Comparison of total MMSE scores and individual
factor scores between MCI patients with and without
sleep disorders are shown in Table 4. There was no
significant difference in total MMSE scores between
MCI patients with and without the above disorders.
The attention and calculation, reading and language
understanding, and visuospatial function scores in MCI
patients without sleep disorders were significantly
higher than those in MCI patients with sleep disorders
(t = 2.18, P = 0.03; t = 2.32, P = 0.02, and t = 2.31,
P = 0.02, respectively), with no significant differences
in other factor scores between two groups.
Comparison of the MoCA scores. As shown
in Table 5, the total MoCA scores in MCI patients
without sleep disorders were significantly greater
than those in patients with sleep disorders (t = 3.06,
P = 0.00). Comparisons of individual factor scores
showed that the visuospatial and executive functions,
attention, and clock-drawing test scores in patients
without sleep disorders were significantly higher
than those in patients with the mentioned disorders
(t = 3.23, P = 0.00; t = 2.61, P = 0.00, and t = 2.50,
P = 0.01, respectively).
DISCUSSION
In our study, the incidence of sleep disorders and the
effects of sleep quality on cognitive functions have
been assessed. We found that, compared with normal
elderly, MCI patients have noticeably more sleep
problems. The effects of sleep disorders on cognitive
functions are mostly reflected in the state of attention
and reading and language understanding.
It was found that patients with dementia have
obvious sleep rhythm disorders [19], and the incidence
of sleep disorders in AD patients is 25-44% [20]. The
MCI is considered an early symptom or a high-risk
factor for dementia, especially for AD [21]. There is
a higher risk of AD or other types of dementia in MCI
patients with sleep disorders [22]. MCI, similarly to
dementia, is influenced by risk factors including
age, educational level, physical exercise, and sleep
disorders. The incidence of sleep disorders in patients
with dementia was found to be higher than that in
normal elderly. The main manifestations include
obvious sleep-wake rhythm impairment, low sleep
efficiency, a lower percentage of rapid eye movements
(REMs) within the sleep period, frequent awakening,
and shallow sleep [23]. The findings of our study are
consistent with those of previous publications. These
facts show that cerebral systems responsible for the
sleep/wake cycle are mildly but noticeably impaired
in a significant proportion of MCI patients.
The MMSE test combined with MoCA is adopted to
assess the state of cognitive function in the examined
subjects. The MoCA was proposed by Nasreddine et
al. [15] in Canada according to clinical experiences
and cognitive items and scoring methods of MMSE.
It is a rapid screening tool for detecting cognitive
impairment, including 11 detection items in 8 areas,
attention and concentration, executive functions,
memory, language, visuospatial function, abstract
thinking, calculation, and orientation. The total score
is 30, and scores ≥ 26 represent the normal state.
Due to a higher sensitivity, wide coverage range, and
short testing time, MoCA is more suitable for clinical
use. In addition, MoCA is more sensitive in MCI
screening compared to MMSE and can be used for
screening MCI patients with normal MMSE scores.
An MMSE score value higher than delimitation is the
criterion for MCI MMSE. The cognitive impairment
in patients with MoCA scores lower than delimitation
(26 scores) is milder than that with MMSE screening.
Even so, the total PSQI scores in these patients are
significantly different from the control. This indicates
that the sleep quality in MCI patients is much lower
than that in normal elderly, especially for the sleep
duration and habitual sleep efficiency. There were no
significant differences in factor I, II, V, VI, and VII
scores between the two groups.
It should be recognized that coefficients of
correlation between the examined indices calculated
in our study are relatively low. Thus, the respective
correlations are not strong and indicative of only some
trends but not of strong dependences. Nonetheless,
these correlations, due to the sufficiently large
number of subjects in the examined groups, are quite
significant.
As found in a previous study, low sleep quality
will affect cognitive functions (such as learning and
memory) in patients with MCI [24]. In this study, both
MMSE and MoCA scores were found to negatively
correlate with the total PSQI score, especially for
MoCA scores negatively correlating with the scores
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 99
ASSOCIATION BETWEEN SLEEP CHARACTERISTICS AND MILD COGNITIVE IMPAIRMENT
of PSQI factors II, III, and IV. This indicates that poor
sleep quality can also be a factor causing decline of
cognitive functions.
It was also found that, compared with MCI patients
without sleep disorders, the cognitive impairment in
MCI patients with such disorders is mainly reflected
in deficiencies of attention and visuospatial/executive
functions. As was shown in previous studies, the
prefrontal cortex may be more sensitive to lack
of sleep [25, 26]. This lack can lead to significant
metabolic disorders in the brain, especially in the
prefrontal cortex [27]. The prefrontal cortex is closely
related to executive functions, especially to high-
grade ones. It is believed that there is an apparent
connection between functional characteristics of the
prefrontal cortex and those of the sleep/wake system
[28-30]. In addition, lack of sleep may cause a decline
in executive function [31]. Manly et al. [32] found
that sleep deprivation causes visuospatial impairment.
In particular, lack of sleep mainly affects the right
hemisphere, but this viewpoint is not widely accepted.
A study on patients with multiple sclerosis [33]
showed that sleep problems can lead to a sustained
decrease in attention. In patients with the attention
deficit / hyperactivity disorder (ADHD), inattention is
associated with insomnia [34].
In our study, the total PSQI scores in the MCI
group exceeded 6, while those in normal elderly were
more than 5. This indicates that the sleep quality in
persons older than 60 years gradually decreases, and
that sleep disorders are a widespread phenomenon that
merits our great attention. Of course, the assessment of
sleep disorders in the elderly using the PSQI may be
affected by some subjective factors. Multichannel EEG
studies may provide more clinical significance. The
limitations of our study are as follows: (i) The causes
of sleep disorders have not been subdivided; these
causes included breathing-related sleep disorders,
restless legs syndrome, and periodic leg movements.
(ii) Multichannel EEG and video polysomnography
have not been used for the diagnosis of sleep disorders.
It, however, should be taken into account that these
techniques are relatively complex and expensive so
they cannot be successfully applied for examination
of large populations.
This study was conducted in accordance with the Declaration
of Helsinki. The study was conducted with approval from the
Ethics Committee of the First Hospital of the Hebei Medical
University. Written informed consent was obtained from all
participants.
The authors of the report, C. An, L. Yu, L. Wang, G. Jin,
M. Song, Q. Zhu, H. Jia, K. Liu, M. Wang, аnd X. Wang, have
no conflict of interest.
Acknowledgement. This work was supported by the
Science and Technology Support Program of Hebei Province
(No. 09276103D).
К. Ан1,2, Л. Ю1,2, Л. Ван1,2 Г. Джін1,2, М. Сонг1,2, К. Жу1,2,
Х. Джіа1,2 К. Лю1,2 М. Ван1,3, Кс.Ван1,2
ЗВ’ЯЗКИ МІЖ ХАРАКТЕРИСТИКАМИ ПРОЦЕСУ СНУ
ТА ПОМІРНИМИ ПОРУШЕННЯМИ КОГНІТИВНИХ
ФУНКЦІЙ У ЛЮДЕЙ ПОХИЛОГО ВІКУ
1 Перша лікарня Медичного університету Хебей, Шіджіа-
хуан (Китай).
2 Інститут розумового здоров’я Медичного університету
Хебей, Шіджіахуан (Китай).
3 Хебейська лабораторія старіння мозку та когнітивних
нейрофункцій, Шіджіахуан (Китай).
Р е з ю м е
Ми порівнювали показники якості сну у пацієнтів з помір-
ними когнітивними порушеннями (MCI) та літніх людей без
таких розладів і аналізували впливи характеристик проце-
су сну на когнітивні функції. У дослідженні брали участь
320 пацієнтів групи MCI та 630 здорових літніх людей конт-
рольної групи, в яких співпадали вік, стать та рівень осві-
ти. Для оцінки якості сну використовували Пітсбургський
індекс якості сну PSQI, а для оцінки статусу когнітивної
сфери – системи MMSE та MoCA. У групах МСI та контро-
лю було 110 (34.3 %) та 170 (27 %) випадків розладів сну
(P < 0.01). Сумарні значення оцінок PSQI демонстрували ві-
рогідні міжгрупові відмінності; оцінки тривалості сну (фак-
тор III) та звичайної ефективності сну (фактор IV) у гру-
пі MCI були вірогідно нижчими, ніж у контрольній групі.
Загальні оцінки PSQI негативно корелювали з оцінками за
шкалами MoCA та MMSE. Оцінки за MoCA негативно коре-
лювали зі значеннями латентного періоду сну (фактор II),
тривалості сну (фактор III) та звичайної ефективності сну
(фактор IV), тоді як оцінки за MMSE знаходились у негатив-
ній кореляції з бальними оцінками факторів III та IV. Баль-
ні оцінки за шкалами уваги, кількісних розрахунків, розу-
міння читання й мовлення та просторово-зорової функції
за MMSE, а також просторово-зорової/виконавчої функції,
уваги та тесту з малювання годинника за MoCA у пацієн-
тів групи MCI без розладів сну були істотно більшими, ніж
відповідні значення у MCI-пацієнтів з такими розладами.
Таким чином, частота розладів сну у пацієнтів із помірни-
ми розладами когнітивної сфери є вищою, ніж така у здоро-
вих літніх осіб. Впливи розладів сну на когнітивні функції
в основному відображуються в розладах уваги та просторо-
во-зорової/виконавчої функції.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1100
C. AN, L. YU, L. WANG, et al.
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