included in the list are players diagnosed with amyotrophic lateral sclerosis (als) who were never tested "post-mortem" for cte but whose history appears consistent with cte. a typical diagnosis of als has primarily been based on the symptoms and signs the physician observes in the patient and a series of tests to rule out other diseases and therefore, prior to the discovery of cte as a phenomenon in ex-american football players, many cte cases were diagnosed as als. the testing of cte in deceased ex-nfl players began only after the disease was first diagnosed, in 2002, in the brain tissue of mike webster. after then, testing became common practice only gradually. a cohort mortality study run by the national institute for occupational safety and health (niosh) examined 3,349 nfl players who played at least five full seasons from 1959 to 1988. findings showed that while nfl players lived longer than the average american male, the risk of death associated with neurodegenerative disorders was about three times higher among the nfl cohort. the risk for death from alzheimer's disease and als were about four times higher among the nfl cohort.