Jan. 29, 2007 --Multiple sclerosis (MS) may be 50% more common in the U.S. than previously thought, according to a new research review.
The review from the National Institute of Neurological Disorders and Stroke says almost one in 1,000 people in the U.S. have MS.
However, the National Multiple Sclerosis Society says that figure could still be low.
The society points out that the review's estimate of MS prevalence (the number of people with MS) works out to about 266,000 people.
But the society says it has "over 300,000 people" in its database who say they have MS.
The review's researchers included Deborah Hirtz, MD, of the National Institute of Neurological Disorders and Stroke, which is part of the National Institutes of Health (NIH).
They analyzed 500 studies published from 1990 to 2005 to track MS and 11 other neurological disorders. Their findings appear in the Jan. 30 issue of Neurology.
Since high-quality U.S. data on most disorders were lacking, the researchers often applied data from other countries to the U.S. population.
That approach isn't ideal, the researchers admit. They call for better studies to track neurological disorders in the U.S.
Still, they say their findings show "the burden of neurologic illness affects many millions of people in the United States."
Multiple Sclerosis Findings
"Our estimate of MS prevalence is about 50% higher than a comprehensive review from 1982," Hirtz says in an American Academy of Neurology news release.
"Whether this reflects improvement in diagnosis or whether incidence is actually increasing deserves further study," Hirtz says.
How Common Are Neurological Conditions?
In addition to MS, the researchers tracked the prevalence of the following conditions:
- Migraine: 121 in 1,000 people
- Epilepsy : 7.1 in 1,000 people
- Alzheimer's disease : 67 in 1,000 people 65 or older
- Parkinson's disease : 9.5 in 1,000 people 65 or older
- Autism spectrum disorders: 5.8 in 1,000 children
- Cerebral palsy : 2.4 in 1,000 children
- Stroke: 10 per 1,000 people
- Traumatic brain injury: No prevalence estimates available
- MS: 0.9 in 1,000 people
- Spinal cord injury: No prevalence estimates available
- ALS (amyotrophic lateral sclerosis, or Lou Gehrig's disease): 0.04 in 1,000 people
- Tourette's syndrome: No prevalence estimates
Conditions Not Tracked
These conditions aren't necessarily the most common neurological disorders, note Hirtz and colleagues.
And though autism and cerebral palsy are lifelong conditions, data were only available for cases in children.
Trends in Conditions
Those trends are likely due to America's aging population and better diagnosis, according to the review.
Traumatic brain injuries are down by about half since the 1982 review.
"It is likely that this reflects more restrictive hospital admission criteria, although improvements in motor vehicle safety may also contribute," write Hirtz and colleagues.
Previous estimates weren't available for autism spectrum disorders or Tourette's syndrome.
Past data were "too sparse" to track trends in spinal cord injury, the researchers say.
Concerns Over MS Estimates
In a news release, the society says it "applauds the efforts of the NIH to document the importance of neurological disorders."
However, there is "considerable uncertainty about the exact number of people in the U.S. who have MS," says the society.
The society agrees with the reviewers that better studies are needed to improve the accuracy of MS estimates.