HISTORY: WINTER WOES
Mrs. A, age 64, lives alone in an old farmhouse. For approximately 8 months, she had complained of depressed mood, decreased interest, difficulty sleeping, low energy, decreased concentration, and feelings of hopelessness. She met DSM-IV-TR criteria for major depressive disorder with underlying anxiety.
Mrs. A also reported having sinus headaches throughout the fall and winter. Blood chemistry, CBC with differential, thyroid profile including T4& TSH, urine drug screen, urine analysis, and ECG results were normal.
In April, Mrs. A was enrolled in an outpatient study of depression relapse prevention treatment. After taking the active study drug for 2 months, she reported continued low mood, low energy, difficulty concentrating, poor sleep and worsening headaches. Because her depression did not improve sufficiently, she was dropped from the study.
In July, Mrs. A saw a psychiatrist and was started on sertraline, 50 mg/d. By November, the dosage had been increased to 150 mg/d. At this time, she reported unsteadiness, dizziness, frequent falls, and intolerable headaches in addition to her depressive symptoms. She was referred to a neurologist to rule out a neurologic disorder.
Table 1
Symptoms that suggest major depression and/or chronic CO poisoning
| Symptom | Major depression | Chronic low-level CO poisoning |
|---|---|---|
| Depressed mood | + | + |
| Diminished interest | + | - |
| Weight loss | + | - |
| Decreased appetite | + | - |
| Difficulty sleeping | + | + |
| Diminished concentration | + | + |
| Suicidal thoughts | + | - |
| Fatigue, weakness | + | + |
| Headaches | + | + |
| Palpitations | + | + |
| Shortness of breath | + | + |
| Nausea | + | + |
| Abdominal pain | + | + |
| Vomiting | + | + |
| Diarrhea | + | + |
| Confusion | - | + |
| Diminished cognitive function | + | + |
| Sexual dysfunction | + | - |
| + = suggests disorder | ||
| - = does not suggest disorder | ||
| CO = Carbon monoxide | ||
| Source: Diagnostic and Statistical Manual of Mental Disorders (4th ed, rev). | ||
| Copyright 2000. American Psychiatric Association; and Tierney LM, McPhee SJ, Papadakis MA (eds). Current Medical Diagnosis and Treatment. New York: McGraw Hill, 2003. | ||
The authors’ observations
Chronic fatigue syndrome is characterized by severe unexplained fatigue that persists for >6 months. The new-onset fatigue is not abated with rest. Other symptoms include impaired memory or concentration, sore throat, tender lymph nodes, muscle pain, headaches, pain in several joints, and disturbed sleep.1
Mrs. A, however, never complained of sore throat or joint or muscle pain, and her laboratory findings were normal.
Seasonal affective disorder (SAD) is characterized by a temporal relationship between onset of depressive symptoms and a particular time of year (eg, symptoms emerge each winter) for at least 2 years. Full remission also occurs at a characteristic time (eg, each summer).2
Mrs. A’s headaches, frequent falls, dizziness, and difficulties with balance do not suggest SAD. Also, these symptoms have not persisted long enough for an SAD diagnosis.
Thyroid disorder. Hypothyroidism symptoms—particularly low mood, decreased energy, fatigue, psychomotor retardation, and lack of motivation—can mimic depression. Mrs. A’s T4 and TSH readings were normal, however.
Metabolic dysfunction. Symptoms secondary to decreased serum concentrations of sodium, potassium, magnesium, or calcium can mimic depression, but blood tests showed Mrs. A has normal electrolyte levels.
Brain tumor. Patients with a brain tumor can present with mood symptoms, psychosis, headaches, mania, cognitive impairments, seizure problems, and other symptoms depending on the tumor’s size and location.
FURTHER TREATMENT: SUDDEN RELIEF
By late November Mrs. A’s fatigue, once present only mornings, plagued her throughout the day. We considered changing antidepressants because of her complaints and sertraline’s lack of efficacy.
The following month, however, Mrs. A told us that her fatigue and headaches were gone. Mood, sleep, and concentration were also improved. Her Hamilton Rating Scale for Depression score had improved from 21 when she entered the study—indicating moderate severity—to 6, indicating remission. Her neurologic referral was cancelled.
Mrs. A then mentioned that her home’s water heater had been malfunctioning for several months. She said she could not afford to get it repaired during the summer but finally hired plumbers to fix it in late November.
After working all day in Mrs. A’s basement, two workers suffered acute headaches and nausea. The symptoms prompted the workers to search the basement for a carbon monoxide leak; they found a small leak in the water heater, which they replaced.
The next morning, Mrs. A said, her headache disappeared. Her other symptoms were gone within 4 days.
The authors’ observations
The sudden disappearance of Mrs. A’s symptoms after her water heater was replaced and emergence of severe physical symptoms in the two plumbers suggest carbon monoxide (CO) poisoning, a common and potentially lethal medical problem.
Low-level CO poisoning usually results from repeated exposure to incomplete combustion in a defective heating appliance, such as a water heater (Box 1).3,4 Symptoms usually surface in the winter, when heating appliance use peaks and windows are left closed, allowing indoor CO to accumulate in high concentrations.7
Indoor heating systems: Leading cause of death by CO poisoning
Carbon monoxide (CO) poisoning is preventable yet causes more than 2,000 deaths each year in the United States.3,5 CO poisoning may result from intentional or accidental exposure to motor vehicle exhaust, malfunctioning home heating systems, and improperly vented combustion appliances.
Indoor heating systems account for about 75% of CO poisoning-related deaths.5 Fatal CO exposure has also been attributed to charcoal grills/burning charcoal, gas water heaters, camp stoves, lanterns, kitchen gas ranges/ovens, and other fuel-burning products.5
Although most states do not require residential use of CO detectors, clinicians should encourage patients to install at least one CO detector near their beds.5,6