Causes of Daytime Sleepiness
Excessive daytime sleepiness can be caused by multiple factors including sleep disorders, medical conditions, medications, and lifestyle factors, with obstructive sleep apnea, insomnia, and narcolepsy being among the most common medical causes. 1
Primary Sleep Disorders
Obstructive Sleep Apnea (OSA): Characterized by repeated episodes of upper airway obstruction during sleep, leading to oxygen desaturation and sleep fragmentation. Signs include snoring, observed apneas, morning headaches, and dry mouth upon awakening. OSA affects approximately 24% of older adults and is a significant cause of daytime sleepiness. 1, 2
Narcolepsy: A neurological disorder characterized by excessive daytime sleepiness, cataplexy (sudden loss of muscle tone triggered by emotions), hypnagogic hallucinations, sleep paralysis, and disrupted nocturnal sleep. Narcolepsy has an overall prevalence of 0.05% with a slight male predominance. 1
Idiopathic Hypersomnia: Presents with excessive daytime sleepiness despite normal or prolonged nocturnal sleep duration (>10 hours). Patients may experience memory lapses, concentration problems, and automatic behaviors. 1
Restless Legs Syndrome (RLS): Characterized by uncomfortable sensations and an urge to move the legs, typically worse at night and with inactivity. These symptoms can significantly disrupt sleep and cause daytime sleepiness. Low ferritin levels (<45-50 ng/mL) can be a treatable cause. 1
Circadian Rhythm Sleep Disorders: Include advanced sleep phase disorder (common in older adults), delayed sleep phase disorder, and shift work disorder. These disorders involve misalignment between the internal circadian clock and external environment, leading to excessive sleepiness during desired wake times. 1, 2
Medical and Psychiatric Conditions
Neurological Disorders: Parkinson's disease, post-traumatic brain injury, multiple sclerosis, stroke, and Alzheimer's disease can all cause excessive daytime sleepiness. 1, 3
Endocrine Disorders: Hypothyroidism can cause fatigue and excessive sleepiness. 1, 4
Psychiatric Conditions: Depression, anxiety disorders, and bipolar disorder are commonly associated with sleep disturbances and daytime sleepiness. 1, 3
Other Medical Conditions: Congestive heart failure, chronic obstructive pulmonary disease, gastroesophageal reflux disease, hepatic encephalopathy, and chronic pain can all contribute to poor sleep quality and subsequent daytime sleepiness. 5, 6
Medication and Substance Effects
Prescription Medications: Many medications can cause sedation, including benzodiazepines, opioids, antihistamines, antidepressants, antipsychotics, and certain antihypertensives. 1, 6
Substance Use/Abuse: Alcohol and recreational drugs can significantly disrupt sleep architecture and cause daytime sleepiness. 1, 3
Lifestyle and Environmental Factors
Insufficient Sleep: One of the most common causes of daytime sleepiness is simply not getting enough sleep (sleep deprivation). 6, 7
Poor Sleep Hygiene: Irregular sleep schedules, excessive time in bed due to fatigue, unplanned naps, exposure to screens before bedtime, and uncomfortable sleep environments can all contribute to poor sleep quality. 1
Aging: Normal aging is associated with changes in sleep architecture, including decreased slow wave and REM sleep, increased light sleep (stages 1 and 2), and more fragmented sleep, which can contribute to daytime sleepiness even in the absence of specific sleep disorders. 1, 5
Diagnostic Approach
Sleep History: Assess onset, frequency, and duration of sleepiness, as well as associated symptoms like snoring, witnessed apneas, cataplexy, or restless legs. 1, 6
Screening Tools: The Epworth Sleepiness Scale (ESS) can quantify sleepiness, while the STOP questionnaire can screen for OSA risk. 1, 2
Sleep Studies: Polysomnography (PSG) is essential for diagnosing OSA, narcolepsy, and other sleep disorders. Multiple Sleep Latency Test (MSLT) helps diagnose narcolepsy and idiopathic hypersomnia. 1, 7
Laboratory Tests: Check ferritin levels for RLS, thyroid function tests, complete blood count, and liver function tests to identify medical causes of sleepiness. 1, 3
Common Pitfalls in Evaluation
Assuming all daytime sleepiness in older adults is normal aging - excessive sleepiness is not a normal part of aging and warrants investigation. 1, 5
Focusing only on nighttime symptoms while missing daytime consequences of poor sleep. 4, 6
Failing to recognize that multiple causes of sleepiness often coexist, particularly in older adults with comorbidities and polypharmacy. 1, 5
Overlooking the significant impact of sleepiness on quality of life, safety (driving, falls), and overall health outcomes. 5, 4