The concern over a partner who sleeps more than expected, or who experiences intense daytime sleepiness, often points to a condition known as hypersomnia. Hypersomnia describes feeling extremely sleepy during the day, even after getting what seems like a full night of rest, or needing to sleep for unusually long periods, sometimes exceeding nine hours regularly. Persistent and unrefreshing sleepiness can significantly affect daily functioning, mood, and concentration. Understanding the root cause of this excessive sleepiness is the first step toward finding an effective solution, as the contributing factors range from simple lifestyle habits to underlying medical conditions.
Lifestyle and Environmental Causes
The most frequent cause of excessive sleepiness is simply not getting enough sleep over time, leading to what is called sleep debt. This accumulation occurs when work demands, social life, or family responsibilities consistently cut into the recommended seven to nine hours of sleep for adults. Eventually, the body attempts to compensate by demanding longer sleep periods or involuntary daytime naps.
Poor sleep hygiene also plays a substantial role by reducing the quality of the sleep obtained. Irregular bedtimes and wake times confuse the body’s internal clock, the circadian rhythm, preventing deep, restorative sleep. Environmental disruptions, such as a partner who snores, a room that is too hot or cold, or exposure to blue light from screens before bed, can fragment sleep. High levels of psychological stress or a recent period of intense physical training can also temporarily increase the biological need for sleep.
Primary Sleep Disorders
When excessive sleepiness is not resolved by addressing lifestyle factors, a primary sleep disorder may be the underlying mechanism. Obstructive Sleep Apnea (OSA) is the most common medical cause of excessive daytime sleepiness, where the airway repeatedly collapses during the night. These breathing interruptions cause brief awakenings and drops in blood oxygen levels, leading to highly fragmented sleep that is not restorative. Despite sleeping a full eight hours, the brain has not achieved the necessary deep sleep stages, resulting in severe sleepiness the following day.
Narcolepsy is a neurological disorder where the brain cannot properly regulate sleep-wake cycles, leading to sudden, uncontrollable sleep attacks during the day. It is characterized by the inability to stay alert, often resulting in falling asleep during passive activities. Restless Legs Syndrome causes uncomfortable sensations and an urge to move the legs, primarily at night, which repeatedly disrupts the sleep cycle. These movements prevent entry into deep sleep, creating a sleep deficit that manifests as daytime sleepiness.
Systemic Medical and Hormonal Conditions
Systemic physical illnesses often present with profound fatigue and sleepiness because they interfere with the body’s energy production and metabolism. Hypothyroidism, or an underactive thyroid gland, slows the body’s metabolic processes, which commonly results in feelings of low energy, excessive sleepiness, and weight gain. This is more prevalent in women because the thyroid produces insufficient hormones to regulate the body’s functions.
Anemia, particularly iron-deficiency anemia, is another frequent cause of profound tiredness. Iron is necessary for producing hemoglobin, the protein that transports oxygen to the body’s tissues and brain. When iron levels are too low, tissues do not receive adequate oxygen, leading to weakness and a constant feeling of being run down.
Hormonal fluctuations unique to women can also drive increased sleep needs. Periods of significant hormonal change, such as pregnancy, perimenopause, or severe premenstrual syndrome (PMS), can disrupt sleep architecture or directly cause fatigue. Chronic Fatigue Syndrome (CFS), sometimes called Myalgic Encephalomyelitis (ME), is characterized by extreme exhaustion that is not relieved by rest and is often worsened by physical or mental exertion.
Mental Health and Medication Effects
Sleep disorders are strongly associated with mental health conditions, with depression being a common cause of hypersomnia in adults. In some cases of depression, the symptom is not insomnia but rather a need to sleep ten or more hours per day, or an inability to feel refreshed after long sleep. This excessive sleepiness may be an atypical presentation of a major depressive disorder.
It is important to distinguish between true sleepiness, where a person involuntarily falls asleep in low-stimulus situations, and fatigue, which is a feeling of extreme tiredness or lack of energy. While both are common in depression, objective sleep tests may show that a person with depression-related fatigue is not truly excessively sleepy. Anxiety disorders can also contribute to tiredness because the constant state of worry and hyper-arousal leads to poor sleep quality and mental exhaustion.
Many common prescription and over-the-counter medications list drowsiness as a known side effect. Certain classes of drugs, including sedating antihistamines, muscle relaxants, and some older types of antidepressants, can directly affect neurotransmitters that regulate wakefulness. Additionally, some blood pressure medications, anxiolytics, and certain antibiotics may inadvertently cause sleepiness or fatigue. Reviewing all current medications is a practical step when trying to identify the cause of new or worsening sleepiness.
Next Steps and When to Seek Professional Help
The first step in addressing excessive sleepiness is maintaining a detailed sleep diary for one to two weeks. This diary should track bedtime, wake time, duration of nighttime and daytime sleep, food and caffeine intake, and any observed sleep disruptions, such as snoring. This documentation provides valuable objective data for a medical professional.
If the excessive sleepiness persists despite improving sleep hygiene, a doctor’s visit is warranted. Warning signs that require professional evaluation include observed breathing pauses during sleep, involuntary sleep attacks during the day, or sudden, significant changes in weight or mood. A primary care physician can order initial blood work to screen for common causes like thyroid dysfunction or anemia.
Depending on the initial findings, the physician may refer the person to a specialist. A sleep specialist can conduct an overnight sleep study (polysomnography) to diagnose or rule out conditions like Obstructive Sleep Apnea or Narcolepsy. The partner’s role is one of support, encouraging the medical evaluation, and providing observations of nighttime symptoms.