The number of ALS cases worldwide is expected to increase by 69% over the next 25 years, according to projections in the August 11 Nature Communications. The predicted increase is largely due to the expected aging of the population worldwide, and will be greatest in developing nations, conclude the authors from the National Institute on Aging (NIA) in Bethesda, Maryland.
“This study is a warning,” commented Richard Bedlack of Duke University, who was not involved in the work. “We need a plan to ensure good care for a massively increasing number of ALS patients in the very near future.”
The current incidence of ALS worldwide is 1.9 cases per 100,000 people, with an average age of onset of 62 years (Chiò et al., 2013). Recently released data from the National ALS Registry of the United States, reported prevalence rates of 5 cases per 100,000 U.S. residents in 2013, or a total of 15,908 people (see Aug 2016 news). To determine how rates of ALS might change in the future, the NIA researchers, led by first author Karissa Arthur and principal investigator Bryan Traynor, began with data from 10 studies of ALS incidence in regions across the globe: Libya, the United States, Uruguay, China, Iran, Japan, Taiwan, Europe, Serbia, and New Zealand. Together, these data represent 34% of the world population.
“We tried to include as many countries as possible,” Traynor said, “and to use the highest-quality study possible in each country.” They selected primarily those that were population- or registry-based (rather than those based on prescription data, for instance), published after 1995, focused on ALS specifically rather than the more general diagnosis of motor neuron disease, and used the standard El Escorial criteria for diagnosis. It was not possible to meet all those criteria in every instance, Traynor noted. In particular, there is a paucity of data from Africa, with the most appropriate data from the continent being a study of motor neuron disease in Benghazi from 1986.
Using these data as a baseline, the researchers then drew on projections of aging and population growth from the United States Census Bureau International Programs International Data Base, a publicly accessible resource on worldwide population structures. The team developed a software application to pull the projections from the database and calculate future ALS rates. Traynor is making the application available, and encourages others to use it for their own analyses.
The key point for predicting future ALS cases, Traynor said, is that as time goes on, not only does a population usually grow, but its age structure evolves. Therefore, the proportion of older people, who are at highest risk for ALS, may increase at a rate different from the growth of the population as a whole.
For instance, Iran currently has a large number of young people. Twenty-five years from now, people in that cohort will enter their sixth decade, when ALS risk begins to increase significantly. Based on that population structure, Traynor and colleagues predict the number of ALS cases in the country will rise much more than the overall growth of the population would suggest.
In the 10 regions examined, the researchers predict the number of ALS cases will grow from 80,162 in 2015 to 105,693 in 2040, an increase of 34%. For Europe, they calculated a rise in incidence of 20%; in Uruguay, 29%; in Mainland China, 46%; in Iran, 112%; and in Libya, 117%. In the world as a whole, they predict the number of ALS cases will increase from 222,801 in 2015 to 376,674 in 2040, an increase of 69%. In addition, the authors posit that these calculations are likely to be underestimates, since improvements to healthcare and economic conditions could extend patient survival, and thus and the number of people with ALS at any given time.
“We are showing that there are a large number of people who will be diagnosed with ALS in the near future. They deserve resources,” Traynor said. These kinds of predictions are crucial to help countries plan for future healthcare, and should be especially useful to policymakers in countries with centralized healthcare systems, who must weigh diseases against one another in determining where to put funds for treatment and research, Traynor said.
While many developing countries are coping with even larger and more urgent health needs, including HIV and malaria, “I suspect those countries are going to look different in 2040,” Traynor added, making the case that they should plan now for higher ALS rates in the future.
“I hope that this paper serves as a wake-up call and has a major impact on resource allocation, both public and private,” commented Bedlack. “Clearly the projected increase in ALS incidence justifies a commensurate increase in research funding. It should also raise awareness of the coming need for more, or at least more access to, specialized ALS doctors and multi-disciplinary clinics.”
Such clinics, he noted, represent the standard of care for ALS, but don’t exist in many developing countries. “One option is to attract more clinicians toward ALS specialization, and to build more multi-disciplinary clinics,” said Bedlack. “Since these clinics are not profitable, this path will be challenging in medical systems that are increasingly business-driven.”
Another option for improving access to ALS specialists, he suggested, would be a major investment in an international telemedicine system, connecting patients around the world with existing dedicated clinicians and therapy teams. This would require appropriate billing codes and changes to laws that restrict the practice of medicine across state or international borders. “Movement in this direction should start now,” said Bedlack.
Arthur KC, Calvo A, Price TR, Geiger JT, Chiò A, Traynor BJ. Projected increase in amyotrophic lateral sclerosis from 2015 to 2040. Nat Commun. 2016 Aug 11;7:12408. [Pubmed].