Factors like head trauma or fracture, electric shock, playing some competitive sports, drinking water from private wells, use of herbicides for gardening, and taking specific dietary supplements all may be associated with the development of amyotrophic lateral sclerosis (ALS), according to a new study.
However, larger studies are required to confirm the findings, as only some of these factors reached statistical significance for their association with ALS.
The study, “Clinical and Lifestyle Factors and Risk of Amyotrophic Lateral Sclerosis: A Population-Based Case-Control Study,” was published in the International Journal of Environmental Research and Public Health.
Despite progress in understanding the genetic causes of ALS, little still is known about the clinical and environmental risk factors predisposing an individual to the progressive neurological disease. To date, the only known risk factors include being male, of an older age, and having a family history of ALS.
While epidemiological studies have shown associations between ALS and a large number of environmental risk factors, evidence for each of them is insufficient and inconsistent, and none has been identified as a definite cause of the disease.
A group of Italian researchers now conducted a population-based study, targeting four provinces in both northern and southern Italy, to assess any possible environmental risk factors that may be contributing to the development of ALS.
They examined factors like clinical history — physical trauma, surgery, or blood donation — and lifestyle habits, focusing on food and alcohol intake, smoking status, source of water, and use of supplements. Leisure activities, including playing sports, gardening, and printing photographs, also were assessed.
The risk of ALS was estimated using statistical models adjusted for sex, age, and education level.
The study enrolled 230 participants, including 95 ALS patients and 135 healthy people (controls).
The results indicated that individuals who experienced physical trauma had a possible higher risk of ALS. Head trauma was associated with a 2.6-fold higher risk of developing ALS, while electric shock was linked with a 2.1-fold higher risk.
Further, playing certain sports at a competitive level, such as soccer, skiing, and swimming, is likely associated with increased risk for ALS.
The researchers also found a possible higher risk among people who reported using private wells for drinking water (1.38-fold) and for individuals who used herbicides during gardening (1.95-fold).
Consuming some dietary supplements, particularly those that contain amino acids, also showed a potential association with increased ALS risk. In the southern Italian population, vitamins and minerals such as selenium also were likely associated with a higher ALS risk.
Conversely, people who ate fish three times a week or more had a 73% lower risk of developing ALS.
However, the association between fish consumption and ALS was considerably weaker in women compared with men, and there was no evidence of a dose-response relation, meaning that eating fish more than three times per week was not associated with a decreased risk.
No differences in ALS risk were found in relation to alcohol consumption, according to the researchers. They did, however, find a possible association between ALS and smoking, which is consistent with previous studies.
“The results of the present case-control study suggest a possible association between some non-genetic risk factors and ALS risk, namely trauma, particularly head trauma or fracture, electric shock, some competitive sport activities, use of private wells for drinking water, use of herbicides during gardening and consumption of some specific dietary supplements,” the researchers said.
However, while many potential factors were identified in this study, only head trauma and fish consumption showed significant associations with ALS risk, the team said. This suggests that more studies, with larger populations, are needed to investigate the additional risk factors.
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