Knowing how the symptoms of MS change over time provides good news for patients newly diagnosed with MS, who may feel the disease leads to inevitable and uniform decline in physical functioning. It also offers vital information for public health planners charged with meeting future needs of MS patients.
In their study, the Mayo Clinic researchers provide encouraging evidence that for many patients the disability from MS remains mild -- so much so that of 99 patients who were walking unassisted when examined in 1991, 71 retained that ability in 2001. And only about 20 percent of patients who did not require a wheelchair in 1991 needed one 10 years later.
"The fact that most MS patients don't get progressively worse over 10 years is the really great news," says Moses Rodriguez, M.D., the neurologist who led the Mayo Clinic research team.
Survival was slightly reduced compared with the general U.S. population, however, and 30 percent of patients progressed to a more disabling MS state -- such as needing a cane or a wheelchair -- over the 10-year follow-up period.
The finding that most MS is not as progressively disabling as once thought is counter to the common perception of MS as a disease marked by a steady decline in motor function. These new results are extremely encouraging to the Mayo Clinic researchers, who treat patients in addition to conducting research.
Adds Sean Pittock, M.D., another member of the Mayo Clinic research team: "Natural history studies like this one can provide a long-term benchmark against which outcomes of treatment and placebo groups can be compared, and in addition can help in counseling patients because it can help them envision a likely future."
Significance of the Mayo Clinic Research
The Mayo Clinic research is the first comprehensive and scientifically rigorous natural history of MS to document how the disease changes over 10 years' time. It is important because:
1. Mayo Clinic's unique database of MS patients provides context. Several generations of Mayo Clinic scientists have been systematically studying MS since 1905. While other researchers have performed large-population studies -- notably in London, Ontario, Canada; in Iceland; and in Northern Ireland -- Mayo Clinic's computerized, centralized diagnostic index and excellent record keeping enable researchers to ascertain the status of nearly 100 percent of the MS patients they've studied.
2. In terms of scientific depth and statistical power, it will likely not be repeated. Mayo Clinic doctors tested, interviewed and conducted physical exams from all MS patients studied, a total of 162 living in Olmsted County in 1991. Olmsted is the southeastern Minnesota county in which Mayo Clinic is located. Researchers visited the patients at home or in the nursing home if necessary.
Ten years later, research team members returned to the field to find the same patients -- and found all but one of them. They administered the same battery of tests to document change over time of increasingly severe MS symptoms. These ranged from moderate gait impairment, to the need to use a cane or a wheelchair to get around.
"This astounding continuity of patient base gives the Mayo Clinic study a statistical power rarely seen in studies of living patients, and not likely to be equaled in subsequent efforts," says Dr. Rodriguez.
Multiple Sclerosis at a Glance
MS is a disease of the central nervous system that affects an estimated 200,000 Americans. Neither the cause nor the cure of MS is known. MS is characterized by a pattern of attack and remission of a variety of symptoms. These include numbness or weakness in one or more limbs; uncoordinated or unsteady gait and blurred vision or problems with eye movements. Nerve fibers malfunction to produce MS symptoms when the protective sheath around them is damaged. Researchers suspect the damage may be caused by a virus or by environmental pathogens.
No one knows why, but women are slightly more likely to get MS than men, and northern states' populations face greater risk than southern states' populations. A November 2003 study published in Neurology by the same Mayo Clinic research team upholds this geographic association.