Familial Amyotrophic Lateral Sclerosis, 1850-1989: A Statistical Analysis of the World Literature

Abstract

We present clinical and pathologic data on four previously unreported familial ALS pedigrees and review and analyze by descriptive and exploratory statistical techniques all published cases of familial ALS (1850-1989). In contrast to the age-dependent incidence of sporadic ALS, the age of onset of familial ALS is normally distributed about a mean of 45.7 years (std. dev. 11.3 years). Survival curves for the familial ALS data also demonstrate a skewed distribution with a median survival time of 24 months with 74% surviving at 12 months, 48% at 24 months and 23% surviving at 60 months. The patient characteristics of age at onset of disease, sex and focus of disease onset are unrelated variables and age at onset of disease is the only predictor of survival (Cox's proportional hazard model, chi-square 14.74, p = 0.0001). By applying accelerated failure time models with a log-normal baseline distribution, estimated probabilities for survival adjusted by age at onset were calculated. It was found that the older the age at disease onset, the shorter the survival.