A Retrospective Analysis of ALS Clusters Near Algae Blooms in North Carolina
Objective To examine clinical differences between individuals with amyotrophic lateral sclerosis (ALS) who live near and far from harmful algal blooms (HABs) in North Carolina. Background While 10% of ALS cases are associated with genetic mutations, the rest may have environmental causes. Higher than expected numbers of ALS cases have been identified near HABs in North Carolina using data from death certificates between 1999 and 2020 (unpublished). It is not clear why there might be more ALS cases near HABs. Blue-green algae produce toxins, such as β-methylamino-L-alanine, which are associated with neurotoxicity and ALS. We hypothesize that there might be clinical differences in HAB-associated ALS and non-HAB-associated ALS, which may help to understand why this correlation exists and better manage HAB-associated ALS. Design/Methods We will perform two retrospective cohort analyses comparing individuals with ALS who live far from HABs (more than 50 miles) and individuals with ALS who live near HABs (less than 50 miles). We will first analyze differences in demographics, genetic testing, and symptom onset using an existing RedCap database. We will analyze ALS progression using ALS Functional Rating Scale scores, forced vital capacity, and weight over time. For the second analysis using the Duke electronic medical record, we will examine the percentage of patients with ALS in each region and compare family history, comorbidities, medications, and socioeconomic status. Results Preliminary results reveal that 16.3% of patients with ALS who live far from HABs have a family history of ALS or dementia, compared with 11.8% of those living near HABs. Conclusions This association suggests that higher than expected rates of ALS near HABs are not caused by genetic mutations. Additional analyses are underway which we hope will shed light on the etiology of HAB-associated ALS and eventually lead to new treatments and methods of prevention.
