Activity levels

Given the large list of factors that determine health, which ones were most important in determining whether someone was improving? Dr. Bell felt that the single most useful criterion in gauging overall well-being was how many hours someone spent engaged in upright activity each day: "hours of actually doing something, like work, school, or cleaning; not just sitting around, vegging-out watching TV."

Some people with ME/CFS log only one to five hours of cumulative activity a day, he said (those hours generally aren't consecutive; people might be active for only a few minutes at a time).

Healthy people, or controls, averaged 15 hours of daily activity; the remitting patients, about 13, fairly close to the level of "normals."

Upright activity was the best indicator of relative health in the survey; moreover, Dr. Bell felt it was the most reliable indicator of prognosis and recovery.

"When a person says they are getting better," he said, "it means they can do activities they couldn't do before." Although he posed his rhetorical question about how recovery should be defined, in his own practice he considered activity level and symptom severity in judging status and prognosis.

He warned that prognoses generally seemed poorest among those who remained bedridden for two or more years when they first became ill, and those who experienced particularly bad cognitive problems.

"The severity of the illness at onset is very predictive of the course the illness will take," he said. Worse outcomes were also common among patients who had a bout of infectious mononucleosis, separate from their ME/CFS onset.