The number of new cases of amyotrophic lateral sclerosis (ALS) identified each year (incidence) and the number of people living with the disease (prevalence) appears to be lower in American Indians and Alaska Natives than in white populations.
Further studies are needed to determine the reason for these differences, but researchers suggest that nonwhite populations may have different genetic or environmental risks for ALS.
The study of ALS in subpopulations such as American Indians and Alaska Natives could increase awareness, improve understanding and diagnosis of the disease, and guide treatment and allocation of resources.
The research team, led by Paul H. Gordon at the Northern Navajo Medical Center in Shiprock, N.M., analyzed electronic health records for American Indians and Alaska Natives with ALS for the calendar years 2002 through 2009. They used inpatient and outpatient visit data obtained from the Indian Health Service, an agency of the U.S. Department of Health and Human Services, which provides health care to eligible American Indians and Alaska Natives throughout the United States.
Initially, the researchers found that the incidence (number of new diagnoses) of ALS in the American Indian and Alaska Native population was 0.63 cases per 100,000. However, poor health and younger ages at death in these communities leave fewer people to develop ALS; ALS tends to occur more often in older age. Therefore, after accounting for the fact that white populations tend to have a higher percentage of elderly people, the researchers calculated an "age-adjusted" incidence of 0.92 cases per 100,00 in the American Indian and Alaska Native population – less than the estimated 1.2 to 4.0 cases per 100,000 in white populations.
The age-adjusted prevalence of ALS (the number of people living with the disease any given time) in the study group on Dec. 31, 2005, was 4.12 cases per 100,000 — lower than the prevalence in white populations, which various studies estimate to be between six and eight cases per 100,000.
The researchers published their findings online Feb. 25, 2013, in JAMA Neurology. Read the full report, for a fee: Incidence of Amyotrophic Lateral Sclerosis Among American Indians and Alaska Natives.
It's not known why American Indians and Alaska Natives may have a lower incidence and prevalence of ALS than that of white populations. Some possibilities are:
The researchers note that study limitations may have affected results. These include the possibility that diagnoses were incorrect; the suggestion that using health care records to capture ALS data may be less accurate than door-to-door surveys; the fact that patients in the HIS health care system may also receive care outside the system; and a lack of access to death certificates.
Importantly, the researchers suggested, additional studies are needed to confirm the findings and to determine the cause of the low rate of ALS among American Indians and Alaska Natives.
Evaluation of ALS in the American Indian and Alaska Native subpopulation, the researchers noted, could lead to educational programs designed to improve awareness, understanding, diagnosis and treatment for those individuals. Finding genetic differences that contribute to the lower risk might help researchers better understand the ALS disease process and generate new therapeutic leads.
The identification of race as a risk factor for ALS could help scientists better understand and determine the causes of the disease. (A risk favor is an attribute, characteristic or exposure that increases the likelihood of developing a disease or injury.)
To read more about risk factors in ALS, see: