Sudden bouts of low blood pressure that occur when people walk, stand or conduct everyday activities may explain some cases of chronic fatigue, an affliction that has baffled doctors searching for effective treatments or even a good definition.
Doctors at the Johns Hopkins Children's Center who tested seven fatigued teen-agers discovered that they felt lightheaded and experienced a profound drop in blood pressure when placed on a tilt-table and swung to an upright position.
Dr. Peter Rowe, a Hopkins pediatrician, said the tilt-table test mimicked a real-life problem facing people with chronic fatigue: When they walk or stand, their hearts fail to pump faster and more vigorously to ensure that enough blood reaches the brain and other organs.
Instead, blood tends to pool in the legs and feet. Even modest activity leaves the patients weak, forcing them into bed for hours or even days. Many miss long stretches of school and retreat from social activities.
Several of the Hopkins patients felt better when encouraged to shake more salt on their foods and when given drugs that increased their blood pressure.
"Before, I was almost dead -- I didn't move around, didn't do anything but lay around like a slug," said Casey Lane, 17, a senior at Towson High School. After missing long stretches of school last year, she resorted to home study -- taking her lessons by phone while lying in bed.
"Now, I'm getting active again, hanging out with my friends and going to school," she said.
Although the results are preliminary, Dr. Rowe said the study should at least quash the widely held perception that people are faking their symptoms or suffering from a psychiatric illness. "All were thought to be malingering at times by their physicians, their school systems or their families," Dr. Rowe said.
During a wave of publicity in the 1980s, chronic fatigue syndrome was often disparaged as "yuppie flu." The name was based on the perception, now rejected by many patients and physicians, that a disproportionate number of well-educated, hard-driving professionals were afflicted.
Experts are unsure how many people suffer from chronic fatigue. The federal Centers for Disease Control and Prevention estimates that as many as 10 people out of every 100,000 are afflicted, while a Boston clinic estimates three out of every 1,000.
Scientists have yet to agree on a cause but haven't lacked for theories. Some of the proposed culprits are viruses, immune-system disorders, sleep disorders, environmental agents and depression.
Results of the Hopkins study, directed by Dr. Rowe and cardiologist Hugh Calkins, appear in today's Lancet, a British medical journal.
Dr. Rowe said he reported his findings after studying only seven teen-agers because the tilt-table symptoms were "immediate and profound," as were the results of treatment in four of seven patients.
The physicians recently widened their study to include adults.
All but one of the teens had felt extremely tired for more than six months; the other was successfully treated before the six-month mark. All grew tired from tasks as simple as walking down a hallway.
Dr. Rowe said several met the CDC definition of chronic fatigue syndrome, which includes physical symptoms such as sore throats, sore muscles and aching joints.
Further tests will be needed to confirm the blood-pressure abnormality as a cause of chronic fatigue, Dr. Rowe said.
Even if it qualifies, it may account for some but not all cases.
Dr. Rowe said he began testing fatigued teen-agers on a tilt-table to see if they suffered from the same problem that causes other people to pass out when they change from a flat to vertical position.
The affliction, known as neurally mediated hypotension, is caused by a confusion in electrical signals that run from the brain to the heart. Rather than telling the heart to beat harder when a person stands, the signals tell it to do the opposite.
"It's precisely what you don't need at that point," Dr. Rowe said.
In the study, the patients' blood pressure dropped from an average of 105/64 to 65/40. Two fainted for the first time in their lives. In four, the symptoms occurred after 12 to 23 minutes; the others took longer to feel ill.
"I'm really pleased that this has removed it from the psychiatric realm into the medical realm," said Pamela Acher, 50, a former teacher and member of a local support group, the Chronic Fatigue Immune Dysfunction Syndrome Network of Baltimore. "But I don't think that regulating this inappropriate physical response is going to solve the whole problem."
Ms. Acher, who is taking part in the adult study at Hopkins, said blood-pressure drugs have enabled her to get out of bed more often. But she is far from cured.
"It still doesn't make me able to go down and cook a meal," she said. "I've talked to some people who are doing much better on the program. So far, nobody knows which person is going to respond."