Is central sleep apnea (CSA) associated with Gulf War exposures?

Central Sleep Apnea and Gulf War Exposures

There is no established causal link between Gulf War exposures and central sleep apnea (CSA); however, Gulf War veterans do exhibit a higher prevalence of sleep-disordered breathing, predominantly obstructive sleep apnea (OSA), not central sleep apnea.

Evidence from Gulf War Veteran Studies

The available research on Gulf War veterans demonstrates sleep disturbances but does not support a specific association with CSA:

• Sleep apnea prevalence in Gulf War veterans was 8.3% in a selected cohort, with the vast majority of cases being obstructive sleep apnea-hypopnea syndrome (SAHS), not central sleep apnea 1
• Among 192 self-referred Gulf War veterans evaluated, 46 underwent polysomnography for suspected sleep disorders, and 15 met criteria for SAHS (defined as respiratory disturbance index ≥15), characterized by continued respiratory effort during apneas—the hallmark of OSA, not CSA 1
• CPAP therapy improved symptoms in Gulf War illness patients with sleep-disordered breathing, with therapeutic nasal CPAP producing significant improvements in pain (34%), fatigue (38%), cognitive function (33%), and sleep quality (41%) compared to sham CPAP 2. This response pattern is consistent with OSA treatment, not CSA.

Distinguishing Central from Obstructive Sleep Apnea

Understanding the fundamental difference is critical to answering this question:

• OSA is characterized by continued respiratory effort during apneas (chest and abdominal movement persist despite airway obstruction), while CSA shows absence of respiratory effort during apneic events 3
• The Gulf War veteran studies specifically identified obstructive patterns with continued respiratory effort 1

Known Etiologies of Central Sleep Apnea

CSA has well-established causes that do not include environmental or chemical exposures:

• Heart failure is the most common cause of CSA, particularly presenting with Cheyne-Stokes breathing pattern with cycle lengths of 45-75 seconds 4, 5
• Other established causes include: neurological disorders (stroke, brainstem lesions), atrial fibrillation (shorter cycle length <45 seconds), pulmonary hypertension, renal failure, and medication-induced CSA (particularly opioids and benzodiazepines) 4, 6, 7, 8
• Treatment-emergent CSA occurs in approximately 1% of patients starting CPAP for OSA and typically resolves within 1-3 months 4

Neurophysiological Findings in Gulf War Veterans

Recent research shows brain activity changes during sleep in Gulf War veterans, but these do not indicate CSA:

• Gulf War veterans demonstrate broadband EEG power reductions in frontal regions during both REM and NREM sleep, present in all Gulf War veterans regardless of Gulf War illness or fatigue status 9
• These frontal sleep EEG abnormalities represent altered neural activity patterns but do not constitute or cause central sleep apnea 9

Clinical Approach to Sleep Complaints in Gulf War Veterans

When evaluating Gulf War veterans with sleep complaints:

• Polysomnography is essential to distinguish between OSA (with continued respiratory effort) and CSA (without respiratory effort) 3, 4
• Look for OSA risk factors: obesity, anatomic upper airway abnormalities, witnessed apneas, snoring, morning headaches, and nocturia 3
• Assess for CSA-associated conditions: heart failure symptoms (orthopnea, paroxysmal nocturnal dyspnea, reduced ejection fraction), neurological deficits, atrial fibrillation, renal dysfunction, and opioid use 4, 5, 7
• Obtain medication history focusing on opioids, benzodiazepines, and sedative-hypnotics that can induce CSA 4, 6

Treatment Implications

The distinction matters significantly for treatment:

• OSA responds to CPAP therapy, as demonstrated in Gulf War veterans where therapeutic CPAP produced substantial symptom improvement 2
• CSA treatment depends on the underlying etiology: optimize heart failure therapy for heart failure-associated CSA, discontinue causative medications for drug-induced CSA, and avoid suppressing compensatory Cheyne-Stokes breathing in optimally treated heart failure patients 3, 5
• Adaptive servo-ventilation (ASV) is contraindicated in heart failure patients with reduced ejection fraction and CSA due to increased mortality risk 3, 7

Common Pitfalls to Avoid

• Do not assume all apneas are the same type—polysomnography with assessment of respiratory effort is mandatory to distinguish OSA from CSA 3
• Do not attribute CSA to Gulf War exposures without evidence of established CSA etiologies (heart failure, stroke, medications, etc.) 4, 7, 8
• Do not overlook that fatigue and cognitive symptoms in Gulf War veterans may improve with OSA treatment, as demonstrated by the significant CPAP response 2