ABDSM EXAM 2025-2026 ALL 150 QUESTIONS AND
CORRECT ANSWERS | LATEST VERSION WITH
VERIFIED ANSWERS & DETAILED RATIONALES |
COMPLETE Q&A FOR DENTAL SLEEP MEDICINE
CERTIFICATION | A+ GRADED
SECTION 1 – SLEEP PHYSIOLOGY & PATHOPHYSIOLOGY
1. Which stage of non-rapid eye movement (NREM) sleep is
characterized by the highest arousal threshold and is considered "deep
sleep"?
• A. Stage N1
• B. Stage N2
• C. Stage N3 (slow-wave sleep)
• D. Stage R (REM)
C. Stage N3 (slow-wave sleep)
Rationale: Stage N3, also known as slow-wave sleep or delta sleep, is the deepest
stage of NREM sleep with the highest arousal threshold. It is critical for
restorative functions and growth hormone release. Stage N1 is light sleep; Stage
N2 is intermediate; REM has a variable arousal threshold.
2. Which neurotransmitter, primarily from the tuberomammillary
nucleus, promotes wakefulness and is inhibited by GABAergic neurons
in the ventrolateral preoptic nucleus (VLPO)?
• A. Dopamine
• B. Serotonin
• C. Histamine
• D. Norepinephrine
,C. Histamine
Rationale: The tuberomammillary nucleus is the primary source of histamine in
the brain, promoting wakefulness. The VLPO inhibits these arousal systems via
GABA and galanin to initiate sleep. Other wake-promoting transmitters include
norepinephrine, serotonin, and dopamine, but histamine is the key target of
VLPO inhibition.
3. According to the AASM scoring manual, what is the minimum duration
required to define an apnea?
• A. 5 seconds
• B. 10 seconds
• C. 15 seconds
• D. 20 seconds
B. 10 seconds
Rationale: The AASM scoring manual defines an apnea as a drop in signal
excursion by ≥90% of pre-event baseline, lasting at least 10 seconds. Hypopneas
require a ≥30% drop with either an arousal or ≥3% oxygen desaturation.
4. Which muscle is the primary dilator of the upper airway and most
responsible for maintaining patency during inspiration?
• A. Masseter
• B. Genioglossus
• C. Sternocleidomastoid
• D. Digastric
B. Genioglossus
Rationale: The genioglossus muscle protrudes the tongue and is the primary
pharyngeal dilator. Its activity is reduced during sleep, contributing to airway
collapse in OSA. The masseter is a masticatory muscle; sternocleidomastoid is an
accessory neck muscle; digastric assists in jaw opening.
,5. The Mallampati classification assesses the size of the soft palate
relative to the oropharynx. Which Mallampati score suggests the highest
risk for difficult intubation and is most associated with OSA?
• A. Class I
• B. Class II
• C. Class III
• D. Class IV
D. Class IV
Rationale: Mallampati Class IV indicates that only the hard palate is visible, with
the soft palate, uvula, and tonsillar pillars not visualized. This is associated with
the highest risk for difficult intubation and is strongly correlated with OSA
severity. Class I-III show progressively more oropharyngeal crowding.
6. Which of the following is a characteristic finding on polysomnography
in obstructive sleep apnea?
• A. Prolonged sleep latency
• B. Increased slow-wave sleep
• C. Respiratory effort-related arousals
• D. Decreased REM latency
C. Respiratory effort-related arousals
Rationale: OSA is characterized by recurrent episodes of upper airway collapse
during sleep, leading to respiratory effort-related arousals, oxygen
desaturations, and sleep fragmentation. Sleep latency may be normal or
decreased; slow-wave sleep is often reduced; REM latency may be variable.
7. The "flip-flop switch" model of sleep-wake regulation describes the
interaction between which two brain regions?
• A. Hypothalamus and thalamus
, • B. VLPO and the ascending arousal system
• C. Pons and medulla
• D. Cerebral cortex and basal ganglia
B. VLPO and the ascending arousal system
Rationale: The flip-flop switch model describes the reciprocal inhibition between
the VLPO (sleep-promoting) and the ascending arousal system (wake-
promoting). This bistable system produces rapid transitions between sleep and
wake states.
8. Which of the following is a non-anatomic factor contributing to OSA
pathophysiology?
• A. Retrognathia
• B. Macroglossia
• C. Loop gain instability
• D. Tonsillar hypertrophy
C. Loop gain instability
Rationale: Loop gain refers to the sensitivity of the ventilatory control system.
High loop gain (oversensitive response to CO₂) can perpetuate respiratory
instability and contribute to OSA. Retrognathia, macroglossia, and tonsillar
hypertrophy are anatomic factors.
9. In which sleep stage does the majority of REM sleep occur during a
normal night?
• A. First half of the night
• B. Second half of the night
• C. Evenly distributed throughout the night
• D. Primarily during Stage N3
CORRECT ANSWERS | LATEST VERSION WITH
VERIFIED ANSWERS & DETAILED RATIONALES |
COMPLETE Q&A FOR DENTAL SLEEP MEDICINE
CERTIFICATION | A+ GRADED
SECTION 1 – SLEEP PHYSIOLOGY & PATHOPHYSIOLOGY
1. Which stage of non-rapid eye movement (NREM) sleep is
characterized by the highest arousal threshold and is considered "deep
sleep"?
• A. Stage N1
• B. Stage N2
• C. Stage N3 (slow-wave sleep)
• D. Stage R (REM)
C. Stage N3 (slow-wave sleep)
Rationale: Stage N3, also known as slow-wave sleep or delta sleep, is the deepest
stage of NREM sleep with the highest arousal threshold. It is critical for
restorative functions and growth hormone release. Stage N1 is light sleep; Stage
N2 is intermediate; REM has a variable arousal threshold.
2. Which neurotransmitter, primarily from the tuberomammillary
nucleus, promotes wakefulness and is inhibited by GABAergic neurons
in the ventrolateral preoptic nucleus (VLPO)?
• A. Dopamine
• B. Serotonin
• C. Histamine
• D. Norepinephrine
,C. Histamine
Rationale: The tuberomammillary nucleus is the primary source of histamine in
the brain, promoting wakefulness. The VLPO inhibits these arousal systems via
GABA and galanin to initiate sleep. Other wake-promoting transmitters include
norepinephrine, serotonin, and dopamine, but histamine is the key target of
VLPO inhibition.
3. According to the AASM scoring manual, what is the minimum duration
required to define an apnea?
• A. 5 seconds
• B. 10 seconds
• C. 15 seconds
• D. 20 seconds
B. 10 seconds
Rationale: The AASM scoring manual defines an apnea as a drop in signal
excursion by ≥90% of pre-event baseline, lasting at least 10 seconds. Hypopneas
require a ≥30% drop with either an arousal or ≥3% oxygen desaturation.
4. Which muscle is the primary dilator of the upper airway and most
responsible for maintaining patency during inspiration?
• A. Masseter
• B. Genioglossus
• C. Sternocleidomastoid
• D. Digastric
B. Genioglossus
Rationale: The genioglossus muscle protrudes the tongue and is the primary
pharyngeal dilator. Its activity is reduced during sleep, contributing to airway
collapse in OSA. The masseter is a masticatory muscle; sternocleidomastoid is an
accessory neck muscle; digastric assists in jaw opening.
,5. The Mallampati classification assesses the size of the soft palate
relative to the oropharynx. Which Mallampati score suggests the highest
risk for difficult intubation and is most associated with OSA?
• A. Class I
• B. Class II
• C. Class III
• D. Class IV
D. Class IV
Rationale: Mallampati Class IV indicates that only the hard palate is visible, with
the soft palate, uvula, and tonsillar pillars not visualized. This is associated with
the highest risk for difficult intubation and is strongly correlated with OSA
severity. Class I-III show progressively more oropharyngeal crowding.
6. Which of the following is a characteristic finding on polysomnography
in obstructive sleep apnea?
• A. Prolonged sleep latency
• B. Increased slow-wave sleep
• C. Respiratory effort-related arousals
• D. Decreased REM latency
C. Respiratory effort-related arousals
Rationale: OSA is characterized by recurrent episodes of upper airway collapse
during sleep, leading to respiratory effort-related arousals, oxygen
desaturations, and sleep fragmentation. Sleep latency may be normal or
decreased; slow-wave sleep is often reduced; REM latency may be variable.
7. The "flip-flop switch" model of sleep-wake regulation describes the
interaction between which two brain regions?
• A. Hypothalamus and thalamus
, • B. VLPO and the ascending arousal system
• C. Pons and medulla
• D. Cerebral cortex and basal ganglia
B. VLPO and the ascending arousal system
Rationale: The flip-flop switch model describes the reciprocal inhibition between
the VLPO (sleep-promoting) and the ascending arousal system (wake-
promoting). This bistable system produces rapid transitions between sleep and
wake states.
8. Which of the following is a non-anatomic factor contributing to OSA
pathophysiology?
• A. Retrognathia
• B. Macroglossia
• C. Loop gain instability
• D. Tonsillar hypertrophy
C. Loop gain instability
Rationale: Loop gain refers to the sensitivity of the ventilatory control system.
High loop gain (oversensitive response to CO₂) can perpetuate respiratory
instability and contribute to OSA. Retrognathia, macroglossia, and tonsillar
hypertrophy are anatomic factors.
9. In which sleep stage does the majority of REM sleep occur during a
normal night?
• A. First half of the night
• B. Second half of the night
• C. Evenly distributed throughout the night
• D. Primarily during Stage N3
