What is the sleep diagnosis for a middle‑aged patient with early‑onset Alzheimer’s disease who has an irregular sleep‑wake cycle, withdrawal, confusion, aphasia, increased muscle tone, and temporal‑lobe dysfunction on PET scan?

Irregular Sleep-Wake Rhythm Disorder (ISWRD)

This patient has Irregular Sleep-Wake Rhythm Disorder (ISWRD), a circadian rhythm sleep-wake disorder characterized by the absence of a clear sleep-wake pattern, commonly seen in neurodegenerative diseases like Alzheimer's disease.

Diagnostic Reasoning

The clinical presentation fits ISWRD precisely based on the American Academy of Sleep Medicine guidelines 11111:

• Irregular sleep-wake cycle on sleep logs - This is the hallmark finding. The patient lacks a clear circadian pattern of sleep-wake behavior
• Neurodegenerative disease context - ISWRD is observed more commonly among patients with neurodegenerative disorders like Alzheimer's disease 11
• Fragmented sleep pattern - The disorder manifests as prolonged periods of wakefulness during typical nocturnal sleep episodes plus excessive sleepiness and prolonged sleep bouts during daytime hours 11

Why Not Other Circadian Rhythm Disorders?

The guidelines clearly distinguish ISWRD from other circadian rhythm sleep-wake disorders 111:

• Not Delayed Sleep-Wake Phase Disorder (DSWPD) - This would show a consistent delay in sleep timing, not irregular fragmented patterns
• Not Advanced Sleep-Wake Phase Disorder (ASWPD) - This would show consistently early sleep and wake times, not irregular patterns
• Not Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD) - This requires documentation of progressively shifting sleep-wake times over at least 14 days, showing a clear pattern of delay or advance. The patient's pattern is irregular, not progressively shifting

Diagnostic Criteria Met

According to AASM guidelines 11:

• Multiple non-circadian sleep-wake bouts documented on sleep logs
• Minimum 7 days of documentation required (which the patient has via sleep logs)
• Associated with neurodegenerative disorder (early-onset Alzheimer's disease)

Clinical Context

The additional neurological findings (withdrawal, confusion, aphasia, increased muscle tone, temporal lobe dysfunction) are consistent with Alzheimer's disease progression 23. Sleep disruption occurs even in early-stage AD patients 2, and as the disease progresses, there is a breakdown of the circadian sleep-wake rhythm with significant amounts of poor-quality daytime sleep 24.

ISWRD poses particular challenges for caregivers 11 and is a significant cause of stress that frequently leads to institutionalization 5.