| Description |
- Background: The distribution of amyotrophic lateral sclerosis (ALS) across the world appears to be uneven, which may in part be explained by environmental factors. β-methylamino-L-alanine (BMAA), a neurotoxin produced by cyanobacteria, and cyanobacterial harmful algal blooms (CHABs) have been associated with increased ALS risk in Guam, northern New England, Maryland, southern France, and Italy. Based on spatial and temporal maps of ALS mortality and CHABs, there appears to be an association between increased ALS risk and CHABs in Eastern North Carolina.
Methods: Using death certificate data and maps of algal blooms generated from satellite data, we identified a region in Eastern North Carolina which has a high rate of ALS mortality and is also near (within 50 miles of) CHABs. We looked for clinical differences between individuals with ALS in this region and those in a control region in Central North Carolina which has normal rates of ALS mortality and is far (more than 50 miles from) CHABs. Two retrospective analyses were performed to compare clinical features of individuals with ALS in the two regions of interest. The first cohort was selected using Epic SlicerDicer. The second cohort, a subset of the first, was selected from an existing REDCap database.
Results: The number of ALS cases per 100,000 in the High Mortality/Near Algae region was confirmed to be more than three times greater than the number in the Normal Mortality/Far from Algae region (p=0.26). Family history of ALS or dementia (p=0.4) and ALS genetic testing results did not differ by region (p=0.6). ALS onset age (p=0.15) and ALSFRS-R progression did not differ by region (p=0.75). Comorbidities overlapped, except for polyneuropathy, which appeared only in the High Mortality/Near Algae region top comorbidities. Common medications overlapped, apart from omeprazole and amitriptyline, which were more commonly prescribed in the High Mortality/Near Algae region.
Conclusions: We confirmed a high prevalence of ALS in the High Mortality/Near Algae region. This was not the result of clustering of genetic ALS. Higher prevalence of comorbid neuropathy and use of omeprazole and amitriptyline in the High Mortality/Near Algae region could suggest the presence of an environmental irritant.
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