Researchers at Sweden’s University of Gothenburg say low red blood cell count at a young age is a risk factor for amyotrophic lateral sclerosis (ALS).
Disease onset was also associated with low muscle strength and low body fat during the later teen years.
”One should never overstate conclusions from a first-time study — the results need to be repeated — but we still must say that what we have found is noteworthy,” Maria Åberg, an associate professor of neurobiology and lead author of the article, said in a press release.
The study, “Risk factors in Swedish young men for amyotrophic lateral sclerosis in adulthood,” appeared in the Journal of Neurology.
Since ALS is more common later in life, most studies on predictive factors are done in older populations. Some non-genetic factors such as smoking and low body mass index (BMI) have been linked to higher risk of ALS, though the role of physical fitness remains inconclusive.
With this in mind, researchers sought to investigate potential predictors in young men for ALS in adulthood. They analyzed data from more than 1.8 million Swedish men aged 16 to 25 who had enlisted in the military between 1968 and 2005 and had therefore taken part in the mandatory military exam.
They identified 526 cases of ALS during the 46-year follow-up. Interestingly, researchers found a link between ALS and low red blood cell court at time of enlistment.
“Although changes in EVF [erythrocyte volume fraction] could predict disease progression in patients diagnosed with ALS, there are, to our knowledge, no previous reports indicating lower EVF as an early predictor of ALS,” researchers wrote. “The present observation thus needs further investigation and it is far too early to speculate in mechanisms such as motor neuron and skeletal muscle oxygenation.”
In addition, ALS patients had slightly lower BMIs (21.1) upon enlistment than their peers (21.9), confirming previous observations. But when it came to physical fitness, researchers revealed contradictory findings.
“Some of it indicated that the risk increases if you engage in very strenuous exercise, while other data suggested that physical activity may even be preventive,” researchers wrote, adding that men with weaker hand, arm and leg muscles were more likely to develop the disease.
“In fact, those with the lowest muscle strength had a significant risk of getting ALS 30 years later,” Åberg explained. Despite the study’s large size, she said, “scientists have no answers as to why a particular group has lower muscle strength more than 30 years before becoming sick.”