Common Causes of Persistent Fatigue

Why Am I Still Tired?

Common Causes of Persistent Fatigue

Fatigue is often not caused by one dramatic problem.

More commonly, several smaller factors overlap: fragmented sleep, stress, shift work, hormonal changes, pain, medications, nutritional deficiencies, and sleep-disordered breathing.

The cause may be sleep apnea and burnout—not necessarily one or the other.

In a world where work-life balance often leans heavily toward work, it is important to assess the whole picture. Trying to correct everything at once can feel overwhelming.

A more realistic approach is to identify the most likely contributors, prioritize them, and address them one step at a time.

Sleep quality PAP effectiveness Leg symptoms Hormones Nutrition Medical conditions Mental health Shift work

Poor Sleep Quality and Sleep Fragmentation

Spending eight hours in bed does not guarantee eight hours of restorative sleep.

Sleep may be repeatedly interrupted by brief arousals that are too short to remember the following morning. Each interruption can pull the brain away from deeper sleep or REM sleep, even when the person believes they slept through the night.

Obstructive sleep apnea Snoring and flow limitation Respiratory-effort arousals Insomnia Chronic pain Leg movements Nocturia Noise or light Stress and hyperarousal Medications or substances

You can remain technically asleep while your brain repeatedly loses the continuity required for restorative sleep.

Still Tired on CPAP or BiPAP?

A low machine-reported AHI is encouraging, but it does not always tell the entire story.

Some patients continue to experience subtle sleep-disordered breathing while using CPAP or BiPAP, including flow limitation and Respiratory Effort-Related Arousals (RERAs).

In one study, additional testing identified residual sleep-disordered breathing in almost half of symptomatic CPAP users whose machine-reported AHI appeared normal. The additional findings included REM-related events, RERAs, and hypoxemia.

Journal of Clinical Sleep Medicine: Residual sleep-disordered breathing during CPAP

Why Can Symptoms Continue?

Under-compensation Pressure may be insufficient to fully control flow limitation, snoring, or obstruction during REM sleep or while sleeping on the back.

Overcompensation Pressure that rises unnecessarily or feels uncomfortable may create awakenings, mask disruption, aerophagia, or difficulty returning to sleep.

Micro-leaks Small or intermittent leaks may create noise, airflow across the eyes or skin, pressure instability, dryness, or repeated brief arousals.

Mask interface Different mask styles may require different pressures and can produce different leak, comfort, and residual-event patterns.

Nasal restriction Congestion, allergies, dryness, or structural restriction may increase breathing effort and reduce treatment comfort.

Non-respiratory arousals Pain, movements, insomnia, stress, or environmental disturbances can remain even when respiratory events are well controlled.

Research comparing nasal and oronasal masks has found that leak, residual respiratory events, and arousals may differ depending on the interface and individual patient.

PubMed: Mask interface, residual events, leak and arousals during CPAP

Effective PAP follow-up should review symptoms, pressure behaviour, flow patterns, comfort, leak trends, mask fit, sleep position, and response to treatment—not only the AHI displayed on the machine.

Equipment Hygiene and Comfort

Masks, cushions, humidifier chambers, and tubing collect moisture, skin oils, mineral deposits, and environmental material over time.

Current research does not show strong evidence that normally used PAP equipment commonly causes serious infections. However, neglected equipment can develop unpleasant odours, visible residue, poor mask sealing, and airway or skin irritation—all of which may reduce comfort and contribute to disrupted sleep.

Clean equipment cannot correct an inappropriate pressure or untreated sleep disorder, but basic maintenance remains an important part of comfortable and consistent therapy.

PubMed: Positive airway pressure device care and cleaning practices

Leg Symptoms, Iron Stores and Magnesium

Leg symptoms can be an overlooked contributor to fragmented sleep.

Patients may describe discomfort mainly in the calves, although symptoms can occur elsewhere in the legs. The exact feeling matters.

Restless Legs-Type Symptoms

Often include:

An urge to move the legs
Crawling, pulling, tingling, or internal restlessness
Symptoms that worsen during rest
Symptoms that are worse in the evening or at night
Temporary relief with movement

Low iron stores may contribute in susceptible patients, even when a standard hemoglobin result is normal. Ferritin is commonly assessed when Restless Legs Syndrome is suspected.

Muscle Cramps or Twitching

May involve:

Painful calf tightening
Visible muscle twitching
Symptoms after exertion
Dehydration or electrolyte loss
Medication effects
Nerve, vascular, or musculoskeletal causes

Magnesium deficiency is one possible contributor, but calf cramps are not a reliable diagnosis of low magnesium by themselves.

Calf discomfort may offer a clue, but it cannot tell us on its own whether ferritin, magnesium, circulation, nerves, medications, or another factor is responsible.

Magnesium supplements are often promoted for cramps and sleep. Some individuals report benefit, but clinical evidence is mixed, and routine supplementation does not help every type of nocturnal leg cramp.

Testing and clinical review are especially important when symptoms are persistent, one-sided, associated with swelling or weakness, or occurring alongside multiple medications or heart, kidney, neurological, or vascular conditions.

Hormones, Perimenopause and Sleep in Women

Hormonal changes are an important—and often under-recognized—part of sleep health.

During perimenopause and after menopause, declining estrogen and progesterone occur alongside changes in body-temperature regulation, sleep continuity, mood, and upper-airway stability.

The risk of obstructive sleep apnea rises after menopause, and sleep apnea in women is still frequently overlooked or diagnosed later than it should be.

PubMed: Effects of menopause on obstructive sleep apnea

Why Can Sleep Apnea Look Different in Women?

Compared with the classic male presentation, women may be more likely to report:

Insomnia Frequent awakenings Fatigue Morning headaches Mood disruption Non-restorative sleep Subtle snoring Brain fog

On sleep testing, women may also show more flow limitation or respiratory-effort arousals and fewer long apneas with severe oxygen drops, particularly before menopause.

This does not mean women cannot develop severe oxygen desaturation or severe OSA. They can. It means that, on average, some women may arouse earlier in the obstructive process, before oxygen falls as dramatically.

A less dramatic oxygen graph does not automatically mean the sleep disruption is insignificant.

Repeated respiratory arousals can still activate the sympathetic nervous system throughout the night. The person may not remember waking, yet the repeated fight-or-flight response can fragment sleep and contribute to insomnia, fatigue, racing thoughts, and non-restorative sleep.

This is one reason symptom history, respiratory disturbance index, flow limitation, arousals, and treatment response may be particularly important when assessing women—not only oxygen saturation and AHI.

Medical, Nutritional and Medication-Related Causes

Persistent fatigue should not automatically be attributed to sleep apnea, especially when symptoms remain despite effective treatment.

Iron and Nutritional Factors

Low ferritin or iron deficiency
Vitamin B12 deficiency
Vitamin D deficiency
Inadequate protein or calorie intake
Dehydration or electrolyte imbalance

Hormonal and Metabolic Factors

Thyroid dysfunction
Perimenopause or menopause
Pregnancy or postpartum changes
Glucose instability or diabetes
Other endocrine conditions

Medical Conditions

Chronic pain
Autoimmune or inflammatory illness
Heart or lung disease
Neurological conditions
Recent infection or prolonged recovery

Medication Effects

Sedating medications
Some antihistamines
Some pain medications
Certain psychiatric medications
Medication timing or interactions

Supplements and medication changes should not be based on fatigue alone. Appropriate history, physical assessment, medication review, and laboratory testing may be required to identify what is actually present.

Stress, Burnout and the Work-Life Imbalance

Burnout and sleep disorders can exist at the same time and reinforce one another.

High workload or emotional stress

↓

Shorter or more fragmented sleep

↓

Less energy and reduced coping capacity

↓

More stress, caffeine reliance, and disrupted routines

Anxiety, depression, grief, chronic stress, and occupational burnout may all contribute to fatigue, insomnia, physical tension, reduced motivation, and difficulty recovering—even when sufficient time is technically allocated for sleep.

Treating sleep-disordered breathing can remove one burden. It may not remove the workload, grief, pain, or burnout that developed alongside it.

This does not make treatment unsuccessful. It means recovery may require more than one step.

Shift Work and Irregular Schedules

Shift work affects people across nearly every essential industry:

Physicians Nurses First responders Police Grocery workers Casino staff Event crews Bartenders Servers Transportation workers Factory workers Caregivers

Night work, rotating shifts, early starts, split shifts, and rapidly changing schedules can force sleep to occur at a time when the circadian system is promoting wakefulness.

Shift work can contribute to insomnia during the intended sleep period and excessive sleepiness during work. It has also been associated with fatigue, impaired performance, accidents, distress, and burnout.

PubMed: Assessment and management of shift-work sleep disruption

Many people cannot simply stop working shifts. Recognizing the biological strain is not about blaming the worker—it is about finding realistic ways to reduce harm.

Protect a sleep window Keep the main sleep period as consistent as the schedule realistically permits.

Use light strategically Bright light may support alertness at work, while reducing morning light may help daytime sleep.

Control the environment Use darkness, cooler temperature, and noise reduction for daytime sleep.

Plan caffeine timing Use it earlier in the shift and avoid it close to the intended sleep period.

Assess for another disorder Shift work does not exclude sleep apnea, insomnia, RLS, or other conditions.

Prioritize safety Severe sleepiness while driving or working requires immediate attention.

Several Problems Can Be True at the Same Time

A patient may have sleep apnea, low ferritin, chronic pain, perimenopausal sleep disruption, and occupational burnout simultaneously.

CPAP can treat the obstructed airway.

It cannot independently correct every other contributor.

Improvement may happen in layers: breathing first, then sleep continuity, then energy, routines, physical activity, mood, and broader health.

The goal is not to solve every possible issue in one appointment.

The goal is to identify the most meaningful patterns, decide what requires testing or referral, and move forward step by step.

In the next section, we will explore the “fatigue snowball,” why CPAP may improve symptoms completely or only partially, and how SleepEZ reviews fatigue from a global rather than numbers-only perspective.