Los Angeles and San Francisco Bay Area Metropolitan Amyotrophic Lateral Sclerosis (ALS) Surveillance Project

Background: ALS is a fatal, rapidly progressive neurological disease. Few population-based surveillance systems and registries exist for neurological diseases such as ALS, making calculation of incidence rates and impact assessment difficult. As part of a nationwide surveillance effort, funded by ATSDR in support of the National ALS registry, retrospective surveillance was conducted in two diverse metropolitan areas:  Los Angeles County (LA) and the San Francisco Bay Area (SFBA).

Methods: We contacted ALS treatment centers, hospitals, and practicing neurologists to identify cases. Case eligibility criteria included residency in SFBA or LA, and treatment for or diagnosis of ALS between January 01, 2009 and December 31, 2011. Case reports included demographic and clinical data; these were de-duplicated and used to calculate incidence rates.

Results: We identified 1085 cases, 540 in SFBA, (150% of expected cases) and 545 in LA (69% of expected); 618 were incident cases. Cases were more likely to be male and White with an average diagnosis age of 61.5yrs. There were significantly more cases (p<0.05) in LA who were foreign-born (LA: 22%; SFBA: 14%), Black (LA: 10%; SF: 6%) or Hispanic (LA: 19%; SF: 10%). Conversely, the age-adjusted incidence rates (per 100,000) were significantly higher in SFBA for Whites (LA: 1.4; SFBA: 2.49) and Hispanics (LA: 0.66; SFBA: 1.57) compared to whites and Hispanics in LA. Both areas had a similar number of reporting neurologists despite differences in population and geographic size. 

Conclusions: General case demographics and incidence rates in ALS cases in these two areas were similar to published studies. However, the differences between the two areas raise questions about how factors such as geography, access to care, and referral patterns affect case ascertainment and diagnosis.