Italian researchers have investigated a cluster of amyotrophic lateral sclerosis (ALS) in Briga, a region of northern Italy known for severe heavy metal pollution, and found no concrete evidence of excess ALS incidence — highlighting the need to carefully infer ALS clusters from mortality data analysis.
The study, “Incidence of amyotrophic lateral sclerosis in the province of Novara, Italy, and possible role of environmental pollution,” appeared in the scientific journal Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration.
The team found that when it compared the Briga area with the rest of Novara, the incidence of ALS was not higher than what would otherwise be expected A previous study on the distribution of ALS-related deaths from 1980 to 2001 had identified Novara as one of 16 high-mortality clusters linked to ALS, with Briga at the center of this cluster.
Delving further into the discrepancy, the team — led by Dr. Marco Vinceti of the University of Modena’s Environmental, Genetic and Nutritional Epidemiology Research Center (REAGAN) and Reggio Emilia of Modena — analyzed the incidence of ALS between 2002 and 2012 in Novara. They identified 106 such cases, 35 of them from the Briga area. In Novara as a whole, the prevalence of ALS was 3.98 per 100,000 inhabitants, compared to 4.65 per 100,000 for Briga alone — a statistically insignificant different.
“Overall, our study did not confirm previous findings of an excess ALS incidence in an area characterized by severe environmental heavy metal pollution,” they concluded, adding that the possible relationship between environmental pollution and the risk of ALS is “worth further investigation.”
Worldwide, ALS affects two to four of every 100,000 inhabitants annually. However, certain areas such as the Pacific Rim are especially at risk, with particularly high ALS rates observed in Guam and western New Guinea.
No one fully understands what exactly causes ALS. Scientists think genetic as well as environmental factors including heavy metals, solvents and pesticides may contribute the development of the disease.