Motor neuron diseases are on the increase in Europe, study finds

Cases of motor neuron diseases — including amyotrophic lateral sclerosis (ALS), the most common of these — are increasing in European countries. A study suggests the reason is not solely because of an aging population, though more people are living longer and neurodegenerative diseases are more common in older adults. The researchers called for more studies on the causes of these diseases and how they can be prevented.

“We are not currently able to put forward other explanations with certainty, although we suspect that improved awareness of the disease has also led to better case detection,” Octave Guinebretière, MD, PhD, an epidemiologist at Pitié-Salpêtrière Hospital in Paris, said in a press release from the Paris Brain Institute, which led the study with the Karolinska Institutet in Stockholm.

The study, “Drivers of Rising Prevalence in Major Motor Neurodegenerative Diseases Temporal Trends in Sweden and France (2003–2022),” was published in Neurology.

More people worldwide are living with ALS, Parkinson’s disease, and multiple sclerosis (MS). Yet it’s not clear whether this is mainly because patients are living longer after diagnosis. The researchers looked at a pair of comprehensive databases for clues.

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Different diseases, different reasons?

For their study, the researchers drew on health databases from France and Sweden, covering several hundred thousand people over nearly two decades, to look at disease prevalence and incidence. Prevalence refers to the number of people living with a disease at a given time, and incidence refers to the number of new cases diagnosed each year.

“Although there are differences between these databases, which we account for in our analysis, they are highly comparable,” said Guinebretière, the study’s first author. “Both countries have high-performing, centralized healthcare systems with universal coverage. These administrative health databases allow us to describe population health in a satisfactory way, drawing on data from reimbursable care.”

The researchers looked at data from the French National Health Data System from 2009-2002 and the Swedish national health registers from 2001-2016. They found that prevalence increased for all three diseases. Pooled data from the two countries showed the prevalence of ALS and other motor neuron diseases increased by 2.8% each year.

The prevalence of Parkinson’s disease increased by 1.4%, and the prevalence of MS by 2.9%.

When the researchers adjusted data to account for differences in aging populations, they found the incidence of Parkinson’s disease actually decreased. The incidence of MS remained stable, and the incidence of motor neuron diseases increased.

The results indicate that the reasons for increases in prevalence may differ across diseases.

The rise in MS cases reflects the fact that patients are living longer after being diagnosed, perhaps due to more effective treatments that slow the progression of the disease. For Parkinson’s disease, prevalence is rising more slowly, and incidence is decreasing. The researchers said the decrease in incidence could be due to a shift toward less exposure to environmental factors, such as pesticides, which are known disease risk factors.

ALS and other motor neuron diseases showed a different pattern. More than half (56%) of the increase in incidence can be explained by aging, the researchers said. Motor neuron diseases are more common in older adults, with a median age at diagnosis of 69 in both France and Sweden.

Better awareness and improved diagnosis may contribute to the increasing number of cases of motor neuron diseases, according to the scientists. Environmental or lifestyle factors may also be contributing, since cases are not evenly distributed across regions, they said.

The findings suggest no immediate public health crisis, the researchers noted, though they highlighted the need for better healthcare system planning and continued research to understand why ALS appears to be becoming more common. They said they hope their work will help inform public policy.

“Our algorithms are now robust enough to envisage drawing up a Europe-wide map of neurodegenerative diseases, in order to better detect and understand their risk factors,” said Thomas Nedelec, MD, PhD, the study’s corresponding author and a researcher with the Paris Brain Institute. “Beyond Sweden, we are already developing collaborations with Denmark and Germany.”