A new study suggests ALS and MS may share an environmental cause, with researchers uncovering a strong geographic association between the two diseases. This discovery may help pinpoint contributing factors and inform future treatment approaches.
A new study published in Nature’s Scientific Reports has unveiled a surprising geographic association between amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), suggesting a potential shared environmental cause. This discovery challenges previous research and offers new avenues for understanding these debilitating neurological diseases.
According to the study, ALS and MS exhibit a strong geographic correlation, even after accounting for variables such as race, gender, wealth, latitude and access to neurological health care.
“The results of the study are surprising because previous studies have typically concluded there was no evidence for a mechanistic or genetic link between the two diseases,” Melissa Schilling, a professor at New York University’s Stern School of Business who conducted the research, said in a news release.
The research employs heat maps to illustrate the geographic patterns of ALS and MS across the United States. Schilling, who specializes in econometrics and large-scale data analysis, began this journey nearly a decade ago after a friend with ALS approached her to examine the data.
“I was very surprised to find such a strong geographic pattern as most of the research on ALS does not emphasize the role of geography. I was even more surprised to find that ALS has a very strong association with the geography of MS,” added Schilling.
One key revelation from the study is the “Simpson’s Paradox,” a statistical anomaly that has likely obscured the relationship between ALS and MS until now. By examining data segregated by gender, researchers observed a strong positive correlation in the geographic distribution of both diseases for men and women separately.
However, this relationship became less apparent when the data were pooled, as ALS is generally more prevalent in men and MS in women.
Historical research has indicated a north-south gradient in MS distribution, leading to theories that factors like UV light or vitamin D might influence the disease. However, supplementation studies produced inconsistent results.
The new findings suggest a more profound geographic correlation between ALS and MS than with latitude, implying a shared environmental factor.
“This finding is important because it suggests that an environmental factor likely plays a significant role in both diseases, and that could provide clues that help us determine what causes them and how they might be avoided or treated,” Schilling added.
Potential environmental factors could include natural elements, such as viruses, parasites, algae and molds, and human-made elements, such as heating oil usage, agricultural practices, industrial processes, mining and chemical contamination.
Schilling highlights the need for more focused geographic comparisons, particularly in unique locations like the Faroe Islands, where MS cases surged after military occupation in the 1940s.
The study’s primary results draw from state-level mortality and demographic data from the U.S. Centers for Disease Control and Prevention WONDER database, supplemented by global mortality data from the World Health Organization.
The consistent findings across different regions underscore the urgency of identifying the underlying environmental factors. As Schilling suggests, a closer examination of distinct geographies might narrow the hunt for the elusive environmental triggers responsible for these diseases.
Source: New York University