Secular Trends of Amyotrophic Lateral Sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a degenerative disorder of the central nervous system characterized by progressive muscle loss caused by the involvement of lower (spinal and bulbar) motor neurons and pyramidal signs caused by the involvement of upper (cortical) motor neurons. Approximately 50% of patients have different degrees of cognitive impairment, ranging from dysexecutive impairment to frontotemporal dementia.^1,2 Amyotrophic lateral sclerosis is familial in 10% of cases and apparently sporadic in the remaining 90%.³ Overall, besides the genetic forms, the cause(s) of ALS still remains elusive. Several exogenous factors have been proposed, namely, cigarette smoking, exposure to electromagnetic fields, heavy metals, organic chemicals, professional sports, occupations related to strenuous work, physical traumas, and personal characteristics, such as lower body mass index and lower educational level, but none of these, with the possible exception of smoking in women, is definitely causative of the disease.⁴ Descriptive epidemiologic studies, in particular on long-term trends of incidence and prevalence rates, may help to elucidate the respective role of genes and environment in the pathogenesis of ALS.