Urinary Neurotransmitters Are Selectively Altered in Children with Obstructive Sleep Apnea and Predict
Cognitive Morbidity.
Leila Kheirandish-Gozal, MD, MSc1, Corena J.T. McManus, MS2,
Gottfried H. Kellermann, PhD 2, Arash Samiei, MD1, and David Gozal, MD1
1. Department of Pediatrics, Pritzker School of Medicine, The University of Chicago, USA
2. NeuroScience, Inc., Osceola, WI
Table 2: Demographic, polysomnographic, and urinary neurotransmitter overnight changes in 20 children with OSA
and preserved GCA scores and 16 children with OSA and low GCA scores.
Introduction
Furthermore, cardiovascular and metabolic morbidities, such as pulmonary
hypertension, systemic hypertension and endothelial dysfunction, insulin resistance.
and serum lipid alterations are also frequently observed (1).
However, identification of those children who have developed any of such OSA
associated morbidities is difficult, and usually complicated by the need for laborious
and onerous test batteries that are not routinely available in most clinical settings. As
such, such assessments are usually not pursued.
In children with OSA, the heightened risk for increased sympathetic tonic and
reactive activity indicative of substantial changes in autonomic nervous system
regulation (2) can for example be conveniently assessed through measurement of
catecholamine levels in urine (3).
Considering the physiological importance of neurotransmitters as signaling
molecules in the nervous system, and the potential alterations that may develop in the
context of OSA, assessment of urinary neurotransmitter offers unique opportunities due
to their stability, sensitivity, and particularly, due to the non-invasiveness of this
approach (4).
General Cognitive Abilities:
A subset of the subjects underwent neurocognitive testing. The neurocognitive assessment included the Core
Subtests of the Differential Abilities Scales (DAS). The DAS is a battery of cognitive tests designed to measure
reasoning and conceptual ability in children, or general cognitive abilities (GCA).
The DAS provides individual subtest scores as well as the following composite scores that were analyzed in the
current study: Verbal, Nonverbal Reasoning, Spatial, and General Conceptual Ability (GCA).
The Verbal Ability cluster (VAB) reflects knowledge of verbal concepts and level of vocabulary development and it is
also indicative of word retrieval from long-term memory. The core subtests administered included Word Definitions,
which measures knowledge of word meanings as demonstrated through spoken language or the ability to formulate
definition of words (verbal fluency). Similarities measures verbal reasoning and knowledge, where inductive
reasoning ability or the ability to relate 3 words to superordinate categories is necessary to earn credit. The
Nonverbal Ability cluster (NAB) measures the child's inductive and sequential reasoning abilities. The core subtests
are Matrices, measuring nonverbal reasoning, which involves perception and application of relationships amongst
abstract figures. Sequential and Quantitative Reasoning involves detection of sequential patterns in figures or
numbers. The Spatial Ability cluster (SAB) measures visuospatial construction ability, spatial memory, and spatial
reasoning. The core subtests are Pattern Construction that measures nonverbal reasoning and spatial visualization in
reproducing designs with colored blocks incorporating response time in the individual scoring, and Recall of Designs
involves the short-term recall of visual and spatial relationships through reproduction of abstract figures.
OSA
Abnormal GCA (n=16)
Normal GCA (n=20)
Age
6.1±1.8
6.2±1.7
Gender (%male)
50%
50%
Ethnicity
68.7
65
BMI Z score
1.30±0.91
1.25±0.87
Apnea Hypopnea Index
12.24±3.2
8.93±4.87
SaO2 Nadir
83.5±5.1
85.6±4.7
TAI (/hrTST)
18.2±8.2
17.1±7.9
GCA score
87.3±13.9
101.2±14.5
Nor-epinephrine
152.3±69.6
90.3±15,7
Epinephrine
120.3±33.8
143.7±30.8
Taurine
-170.3±29.1
-45.8±5.7
<0.0001
GABA
60.2±5.7
38.6±8.0
<0.0001
PEA
-66.9±5.3
-32.4±5.1
<0.0001
<0.01
Overnight Change in: (% change)
Data for changes in urine neutotransmitter level changes are shown as mean ±SEM; all other values are shown as mean ±SD.
Figure 1. Receiver operator curve using cut-off values of overnight changes for 4 urinary neurotransmitters in the prediction of OSA in
children.
Biomarkers
100
The ability score for each subtest is converted to a T score with a mean of 50 and a standard deviation (SD) of 10.
The sum of the core subtests was then converted to yield a total standard score for the Ability cluster, with a mean of
100 and a SD of 15. Although the raw scores were used in the modeling procedures, we express standardized
composite scores for descriptive purposes. The DAS was normalized on a large stratified sample of children across
the United States and has good validity and reliability. The cluster scores are indicative of the “psychometric g”
which is the general ability to perform complex mental processing that involves conceptualization and the
transformation of information, and has been considered as a structural correlate to executive function. For study
purposes, we defined abnormal GCA as ≥ 1 SD below the mean.
80
Sensitivity: 82.0
Specificity: 90.0
Sensitivity
Obstructive sleep apnea (OSA) in children is defined as repeated events of partial or
complete upper airway obstruction during sleep, leading to disruption of normal
ventilation, hypoxemia, and sleep fragmentation. Snoring, the primary symptom of
OSA, effects10-12% of all children. The adenotonsillar hypertrophy, with or without
concurrent obesity, constitutes the major pathophysiological mechanism underlying
OSA in children. Pediatric OSA has been extensively associated with an increased risk
for cognitive deficits and behavioral and mood disturbances.
Methods
P-value
OSA
Criterion : >2
60
40
20
Urinary Neurotransmitters:
Urine samples were collected both prior and immediately after completing the overnight polysomnographic
evaluation in the morning. Children who urinated during the night were excluded from the study. A previously
validated ELISA method for assessment of several neurotransmitters was used. All samples were assayed in
duplicates and values were retained if they were within 10% of each other. Urinary creatinine level was measured for
each sample. Individual urine neurotransmitter levels were corrected for corresponding urine creatinine
concentration.
0
0
20
40
60
80
100
100-Specificity
Figure 2. Receiver operator curves using 3 urinary neurotransmitter defined cut-off values corresponding to individual overnight
changes for prediction of neurocognitive dysfunction in children with OSA.
Results
Hypothesis
OSA in children is associated with unique pattern of alterations in urinary
neurotransmitters, which may reflect underlying cognitive deficits.
Methods
The research protocol was approved by the University of Chicago human research ethics committee.
Informed consent was obtained from the parents, and age appropriate assent was obtained from the
children. Subjects were recruited from the Sleep and ENT clinics of Comer Children’s Hospital, as well
as by advertisement.
Subjects: Children ages 3-12 years were included if they had no genetic or craniofacial syndromes,
chronic diseases such as cardiac disease, diabetes, cerebral palsy and chronic lung disease of
prematurity, or were receiving any psychotropic medications.
Polysomnographic Assessment: A standard overnight PSG evaluation with assessment of 8 standard
electroencephalography (EEG) channels, bilateral electrooculography (EOG), electromyography
(EMG), 2-lead electrocardiography (ECG), oronasal airflow measurement using thermistor, nasal
pressure transducer, and end tidal carbon dioxide (ETCO2), chest and abdominal movement by
respiratory inductance plethysmography, and pulse oximetry including pulse waveform.
Table 1. Demographic, polysomnographic, and urinary neurotransmitter overnight changes in 50 children with OSA and 20 matched
controls.
P-Value
OSA (n=50)
Control (n=20)
Age
6.2±1.6
6.4±1.4
Gender (%male)
54%
55%
Ethnicity
70
70
BMI Z score
1.22±0.78
1.05±0.84
Apnea Hypopnea Index
9.24±0.91
0.37±0.19
<0.001
SaO2 Nadir
84.5±3.9
93.1±2.7
<0.001
TAI (/hrTST)
16.7±6.2
11.1±4.9
<0.04
GCA abnormal
16/36
-
Overnight Change in (% change)
Nor-epinephrine
214.3±23.8
-9.3±3.3
<0.0001
Epinephrine
132.7±10.5
0.8±2.1
<0.0001
Dopamine
13.2±2.9
1.4±0.2
DOPAC
-30.5±4.8
-23.2±3.9
Serotonin
51.6±6.9
38.7±5.6
5-HIAA
-13.8±2.7
-7.8±2.6
Glycine
--23.7±3.8
-16.6±3.2
Taurine
-105.2±11.0
9.8±1.7
<0.0001
GABA
45.2±8.0
-7.8±1.8
<0.0001
Glutamate
9.2±3.6
-17.8±4.7
PEA
-51.4±10.6
-29.5±9.8
Histamine
-40.4±9.3
-44.2±9.6
Data for changes in urine neutotransmitter level changes are shown as mean ±SEM; all other values are shown as mean ±SD.
DG is supported by National Institutes of Health grants HL-065270 and HL-086662
Conclusions
•
Pediatric OSA is associated with overnight increases in urinary concentrations of catecholamines indicative of
heightened sympathetic outflow.
•
Increases in GABA and decreases in taurine could underlie mechanisms of neuronal excitotoxicity or alternatively play a
role in cardiovascular dysfunction.
•
Combinatorial approaches using defined cut-offs in overnight changes of selected neurotransmitters in urine not only
may predict OSA, but also the presence of cognitive deficits. Larger cohort studies appear warranted to confirm the
present findings.
References
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