Tiredness and Chronic Pain Management
“Doctor, I feel tired a lot.” Is this person sleepy, fatigued, depressed, apathetic, or suffering the secondary effects of pain? Certain disorders that generate a daytime condition of drowsiness or fatigue include, but are not limited to:
- Lowered arousal and level of consciousness
- Fatigue due to a reduced energy state
- Depressed mood and anhedonia
- Apathy and lack of motivation
- Sleep apnea
- Testosterone deficiency
- Non-restorative or poor quality of sleep
Lowered Arousal and Level of Consciousness
It is normal to feel drowsy at bedtime or at other times when sleep is desired for cultural and health reasons, such as midday naps (the siesta in Spain and Spanish-speaking countries, the qailula in Arabic-speaking countries). When sleepiness occurs at the wrong time, when one wants to or should be awake and fully alert, it may represent a disorder. Excessive drowsiness, or hypersomnolence, is a disorder of arousal, and in office settings it is the most common level of lowered arousal or consciousness. Some individuals feel sleepy only when passive and understimulated; others are drowsy even when actively engaged.
The Epworth Sleepiness Scale1 is a self-assessment questionnaire to determine the general level of daytime sleepiness, and a score=0 suggests a need for further evaluation to determine the cause of excessive sleepiness. In hospital and nursing home settings, patients may be obtunded (difficult to arouse, confused, requiring constant stimulation to keep awake), stuporous (semicomatose, responding only to vigorous and persistent stimulation; grumbling and moaning) or comatose (no behavioral response to stimulation).
Elevated arousal may occur as well. Mildly demented individuals may compensate for cognitive impairment by hyperalertness. Hypervigilance is common in individuals suffering from Posttraumatic Stress Disorder. Caffeine and other psychostimulants, including medicinal and illicit drugs, may induce hyperarousal. Manic and psychotic patients may become agitated, excited and hyperaroused. In chronic pain management, one finds that hypersomnolence is the most common disturbance of arousal.
Any general medical condition, psychiatric syndrome, sleep disorder or pain itself that interferes with quantity and/or quality of sleep at night will tend to cause residual daytime drowsiness, fatigue, apathy and cognitive disruption. Primary sleep disorders are common and include periodic limb movement disorder (PLMD or restless legs syndrome, RLS), obstructive sleep apnea (OSA), teeth grinding (bruxism), and circadian rhythm disturbances (advanced and delayed sleep phase disorders). Parasomnias such as sleeptalking (somniloquy), sleepwalking (somnambulism), and rapid eye movement (REM) sleep behavior disorders may be found. Narcolepsy may affect as many as 140,000 Americans,2 but it may be underdiagnosed and should be considered. A few patients will not report abnormal phenomena during sleep, but sleep architecture during nighttime polysomnography (NPSG) may reveal paucity or absence of delta sleep (slow-wave sleep, stages III and IV), paucity or absence of REM sleep, or frequent alpha intrusions (electrical arousals or awakenings that might or might not be recalled or reported the next day by the sleeper).
Fatigue and Decreased Energy
Fatigue represents a reduced energy state, described as a sensation of weariness, lessened capacity for work, and decreased efficiency of accomplishment. It may be confined to a single organ. It is normal at some point to experience physiological fatigue, especially after a period of vigorous physical or mental activity. Pathological fatigue occurs in persons who either have not exerted themselves or who encounter fatigue too early during the accomplishment of activities or in disproportion to their intensity or duration.
Various scales such as the Functional Assessment of Cancer Therapy Fatigue (FACT-F), Fatigue Severity Scale (FSS)3 and Modified Fatigue Impact Scale (MFIS) have been used to assess fatigue in specific patient populations such as cancer,4 Parkinson’s disease,5 multiple sclerosis6 and rheumatoid arthritis.7
A differential diagnosis of fatigue includes:
- neurological diseases (multiple sclerosis, traumatic brain injury, Parkinson’s disease)
- infections diseases (mononucleosis, cytomegalovirus infection, chronic hepatitis, acquired immune deficiency syndrome)
- metabolic diseases (thyroid diseases, diabetes mellitus)
- connective tissue disorders (rheumatoid arthritis, systemic lupus erythematosus)
- lymphoma and other carcinomas
A number of prescription medications and drugs of abuse can also cause drowsiness and fatigue. The list of disorders that can cause fatigue is very long, and the medical workup can be extensive and invoke a range of specialty consultations, laboratory studies and diagnostic imaging.
Depressed Mood and Anhedonia
Primary depression is a common cause of fatigue. Depression is pathological sadness not expected as part of normal loss (grief, bereavement). It may be milder and chronic (dysthymia) or moderate to severe and episodic (major depression, bipolar depressed). Most depressed patients have some degree of anhedonia: partial or complete loss of the ability to experience pleasure when anticipating or participating in activities that usually bring joy and gladness. However, depressed mood and anhedonia may be decoupled and occur without the other. Some partially recovered and treated depressed patients may experience remission of painful melancholy, yet they still may not feel complete joy and gladness with normally pleasurable activities. Recovering cocaine addicts may report emotional emptiness and lack of pleasure, even in the absence of depression.8 Anhedonia may be part of a broader apathy syndrome, in which the intensity of all mood and affective states, including reactive pleasure, is undermodulated.
Apathy and Lack of Motivation
Apathy describes a general lack of intensity of most or all emotions not attributable to decreased level of consciousness, cognitive disorder or emotional distress. It is an across-the-board reduction in amplitude of mood and affective states. A common clinical variant is apathy interrupted by sudden and brief outbursts of irritability or agitation if provoked. The differential diagnosis includes abulia, akinesia and akinetic mutism, depression, dementia, delirium, despair and demoralization.9