Life Course Exposure to Cyanobacteria and Amyotrophic Lateral Sclerosis Survival

Cyanobacterial harmful algal blooms (cyanoHABs) occur worldwide and can cause ingestion and inhalation exposure to microcystin and other potent toxins. This study develops life course exposure measures for cyanobacteria for application in population studies and then associates these measures with the survival of individuals with amyotrophic lateral sclerosis (ALS). The exposure measures utilize an individual's residence history, date of disease onset, and satellite data from the Cyanobacteria Assessment Network. Residence duration for selected exposure windows referenced to disease onset date was used to weight cyanobacteria concentrations in water bodies within 0.25 to 10 km of each residence. Different concentration metrics, buffer sizes, and exposure windows were evaluated. The 2.5 and 5 km buffers best balanced the likelihood and plausibility of exposure while still resolving exposure contrasts. Over their lifetime, most study participants lived within 5 km of cyanobacteria blooms, and the exposure was associated with up to 0.89 years shorter survival, with significant interactions for individuals reporting swimming, fishing, and private wells. Our findings suggest a new and modifiable risk factor for ALS survival, and a need to confirm exposures and epidemiological findings. These cyanoHAB exposure estimates can facilitate population studies that can discover new relationships with neurodegenerative and other diseases.