Incidence and prevalence of amyotrophic lateral sclerosis in Harris County, Texas, 1985-1988

Amyotrophic lateral sclerosis (ALS) is sometimes called Lou Gehrig's disease. This disorder affects motor neurons, the nerve cells that control the contraction of muscle cells. As these neurons degenerate, the patient becomes progressively weaker and ultimately dies. In about 80 percent of all cases of ALS, death occurs within five years of the onset of the disease. A curious feature of ALS is that, compared with many other diseases, the incidence (number of new cases) of the disease is essentially constant in all parts of the globe, if one excludes some western Pacific islands where ALS is especially common. Some studies have indicated that the incidence of ALS is increasing. However, it is not certain whether these increases represent a true increase in the disease frequency or an increase in the accuracy with which the disease is being recognized and recorded. A study was conducted to ascertain the number of ALS cases (prevalence) in Harris County, Texas. Cases were identified on the basis of death certificates, the records of neurologists, and records of the Muscular Dystrophy Association. These sources indicated that the incidence of ALS was 1.27 new cases each year per 100,000 men and 1.03 new cases each year per 100,000 women. These rates are lower than some recently reported rates for the northern US, Canada, and northern Europe. Conversely, the rates are higher than those determined by some studies of ALS in southern Europe. No differences were found between blacks and whites. Hispanic men developed ALS at a rate comparable to nonHispanic men. Curiously, however, fewer cases of ALS were found among Hispanic women than would be expected. The overall prevalence of ALS among patients between 65 and 74 years was 33 cases per 100,000 men and 19 per 100,000 women. (Consumer Summary produced by Reliance Medical Information, Inc.)