First US Prevalence Data on ALS

Pauline Anderson

July 24, 2014

The first national prevalence data on amyotrophic lateral sclerosis (ALS) was reported today from the National ALS Registry, using administrative data to ascertain cases of ALS in the United States.

In 2009, the federal Agency for Toxic Substances and Disease Registry (ATSDR), a sister agency to the Centers for Disease Control and Prevention (CDC), implemented the National ALS Registry to collect and analyze data regarding persons with ALS, which is a non-notifiable disease in the United States (except in Massachusetts). The main goals of the Registry, as defined by the 2008 ALS Registry Act, are to describe the incidence and prevalence of ALS better, examine risk factors such as environmental and occupational exposures, and characterize the demographic characteristics of those living with ALS.

In their first report, researchers estimate the overall prevalence of ALS is 3.9 per 100,000 people in the United States, with the highest prevalence (17.0 per 100,000) among those aged 70 to 79 years. Men have a higher prevalence than women (4.8 vs 3.0 per 100,000), and whites a higher rate than blacks (4.2 vs 2.0 per 100,000).

The new report is published online July 24 and appears in the July 25 issue of Morbidity and Mortality Weekly Report (MMWR).

Facilitating Research

ALS is a progressive and fatal neuromuscular disease. Most people with the condition die within 5 years of receiving the diagnosis. There's no known cause, but a hereditary form of the disease, familial ALS, occurs in 5% to 10% of cases.

There is no blood or other test for ALS; diagnosis is based on signs and symptoms and on neurophysiologic tests. There's also no cure, although riluzole (Rilutek, Sanofi-Aventis) has been shown to slow disease progression and has been approved in the United States to treat the condition.

The ATSDR is collecting data from 4 national databases, maintained by Medicare, Medicaid, the Veterans Health Administration, and the Veterans Benefits Administration. Researchers used an algorithm with variables such as international classification codes, a prescription for riluzole, and frequency of visits to a neurologist, to identify people with "definite ALS."

The algorithm, developed during previous pilot projects, was shown to have a sensitivity of 87% and specificity of 85%.

Researchers also used a secure Web portal to identify ALS cases. On this site, patients answer a series of validated screening questions that are very accurate, according to the report authors, led by Paul Mehta, MD, Division of Toxicology and Human Health Science, ATSDR, Atlanta, Georgia. Just over 93% of those who passed the screening questions were determined by a neurologist to have ALS/motor neuron disease.

A total of 12,187 people were identified as having "definitive ALS" across the 4 databases and through the Web portal.

The higher prevalence of ALS among men was observed across all age groups and data sources. The ratio of males to females (1:56) is consistent with other published data, said the authors.

Why whites have a higher prevalence of ALS than blacks is not known and "needs to be investigated further," said the authors.

The registry Web portal included surveys on risk factors, including occupational history, military history, and family history of neurodegenerative diseases, topics that are potentially associated with the disease. From the 1647 respondents who provided information on smoking history, about half were former or current smokers. Of the approximately same number who provided information on alcohol use, fewer respondents identified themselves as former drinkers compared with national estimates.

"Insufficient information is available from the portal data to determine if either smoking or alcohol use is a risk factor in ALS susceptibility," write the authors. "However, compared with national estimates more respondents identified themselves as non-smokers than as current or former smokers."

According to the authors, the reporting of risk factors "is for descriptive purposes only, and inferences should be made with caution. As the Registry matures, it might be possible to draw more conclusions from the data collected through the risk-factor modules."

Educated Patients

Of the 1828 respondents who provided information on educational attainment, 71% reported some college or higher education. Educated patients might be more likely to use the Internet and be more proactive about searching for information on their diagnosis than people with a lower level of education, said the researchers.

Of the 1651 respondents who provided information on military service, almost a quarter (23%) reported a history of military service compared to the national average of 9.1%. Self-selection may have been at play here; service people may have been more likely to volunteer to enroll in the Registry, said the authors.

"Military service has been associated as a potential risk factor for ALS. However, no definitive etiologies related to military service have been identified and further analysis is required."

From the surveys, researchers determined that 76% of patients with ALS were retired or disabled, which isn't surprising given the debilitating nature of the disease and the accompanying mobility issues.

As for employment, educators and healthcare professionals represented the job titles held the longest by respondents. The authors stressed, however, that this doesn't necessarily indicate a correlation between specific occupation or industries and ALS but might reflect a bias toward more educated people self-registering. More research is needed in this area.

Results of surveys on other risk factors, such as pesticide use, will be included in future reports. Exposure to pesticides, heavy metals such as lead, and infectious agents has been associated with an increased risk for ALS. Nutritional intake, physical activity, and trauma have also been identified as possible risk factors.

As the Registry is being used to facilitate ALS research, portal registrants are being sent email messages about clinical trials and studies in which they're eligible to participate.

It is also being promoted on social media, such as Facebook and Twitter, and elsewhere.

The report was limited by possible data entry errors, the inability to measure ALS incidence because the date of diagnosis was not noted in all patient records, and the possibility that information is not representative of all patients with ALS.

Model for Other Diseases?

Dr. Mehta and ATSDR colleagues Kevin Horton, DrPH, MSPH, and Vinicius C. Antao, MD, MSc, PhD, also describe their new findings in a Viewpoint article published online July 24 in JAMA.

"Even in 2014, many conditions are not surveilled in the United States, making it difficult to accurately assess their disease burden," they write. "The approach used for the National ALS Registry provides a novel method to quantify prevalence for a nonnotifiable condition on the national level in the United States.

"Moreover, it is possible that this approach, in part or whole, could be used to help determine the prevalence of other nonnotifiable conditions in the United States (such as Parkinson disease or multiple sclerosis)," they conclude.

MMWR Morb Mortal Wkly Rep. Published online July 24, 2014. Full text

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