Lou Gehrig’s disease, known medically as ALS (amyotrophic lateral sclerosis), is rare. About 34,700 people in the United States are living with it at any given time, and roughly 5,000 new cases are diagnosed each year. That translates to an incidence of about 1.44 new cases per 100,000 people annually, making it far less common than other major neurological conditions like Parkinson’s disease or multiple sclerosis.
ALS by the Numbers
The CDC’s National ALS Registry tracks how many Americans are living with the disease. As of the most recent projections, prevalence sits at about 10.1 people per 100,000 in the U.S. population. That number has been climbing slightly, not because ALS is becoming more common, but because the population is aging and diagnostic methods have improved. The registry estimates cases will rise from roughly 33,000 in 2022 to over 36,000 by 2030, an increase of more than 10%.
To put the rarity in perspective: for every one person diagnosed with ALS in a given year, roughly 150 to 200 people are diagnosed with Parkinson’s disease. Multiple sclerosis is also several times more prevalent. ALS remains one of the least common neurological conditions that most people have heard of, largely because of its severity and the attention it received through the Ice Bucket Challenge and, of course, its namesake Lou Gehrig.
Who Gets Diagnosed and at What Age
ALS is overwhelmingly a disease of middle and older age. The highest prevalence is among people aged 70 to 79, where it affects about 20.2 people per 100,000. Among adults aged 18 to 39, that number drops to just 0.5 per 100,000, making a diagnosis in a younger person exceptionally unusual. Most people are diagnosed somewhere between their mid-50s and early 70s.
Men develop ALS more often than women. The overall male-to-female ratio is about 1.25 to 1, though some estimates range as high as 1.5 to 1. This gap is most pronounced in younger adults, where men are diagnosed at roughly three to four times the rate of women. By older age, the difference narrows considerably to about 1.2 to 1. Researchers suspect that hormonal factors, particularly estrogen, may play a protective role earlier in life, though this isn’t fully established.
CDC data also shows racial differences. Of the roughly 4,861 new cases estimated in 2016, about 77% were in white individuals, 7% in Black individuals, and the rest in other racial groups. Whether this reflects true biological variation or gaps in diagnosis and access to specialty care is still debated.
Sporadic vs. Inherited Cases
About 90% to 95% of ALS cases are sporadic, meaning they appear in people with no family history of the disease. The remaining 5% to 10% are familial, passed down through genetic mutations. A large meta-analysis covering 165 studies found the pooled proportion of familial cases to be about 8%.
One interesting wrinkle: the male-to-female gap nearly disappears in familial ALS, where the ratio is essentially 1 to 1. The higher rate in men is driven almost entirely by sporadic cases, suggesting that whatever environmental or biological factors increase male risk are separate from the inherited genetic pathways.
Why Prevalence Stays So Low
Part of what keeps ALS numbers low at any given time is how quickly it progresses. Median survival from symptom onset ranges from 20 to 48 months, with population-based studies narrowing that window to roughly 20 to 36 months. Because people live with the disease for a relatively short time, the total number of living cases stays small even as new diagnoses continue. About 10% to 20% of patients do survive longer than 10 years, but they are the exception. The short survival time is the main reason ALS prevalence looks so different from conditions like MS, where people often live decades after diagnosis.
Geographic Variation Around the World
ALS rates vary significantly by region. In Europe, annual incidence ranges from about 1.1 per 100,000 in Serbia to 5.6 per 100,000 in Denmark. North American rates fall between 0.5 and 3.3 per 100,000. South American countries report lower rates overall, from 0.26 per 100,000 in Ecuador to 3.2 per 100,000 in Argentina.
The most striking outliers are in Japan. While the broader Japanese incidence is about 2.2 per 100,000, certain regions report dramatically higher rates. The Kii Peninsula has an incidence of 6.4 per 100,000, and the island of Oshima reaches 23.5 per 100,000, the highest recorded anywhere in the world. These clusters have been studied for decades and are thought to involve a combination of genetic and environmental factors unique to those populations. Africa and Oceania have far fewer studies, but available data from South Africa (1.1 per 100,000) and New Zealand (2.9 per 100,000) fall within the typical global range.
Military Veterans Face Higher Risk
One group with a notably elevated risk is military veterans. A 2017 meta-analysis of nine studies found that military service was associated with about a 29% increased risk of developing ALS compared to the general population. The risk was particularly high among veterans deployed during World War II and the Gulf War. Some individual studies reported even larger effects: one found that WWII veterans had nearly five times the odds of developing ALS compared to non-veterans.
The reasons aren’t entirely clear. Possible explanations include exposure to heavy metals, pesticides, or other environmental toxins during service, as well as physical trauma and extreme exertion. The association was strong enough that the U.S. Department of Veterans Affairs recognizes ALS as a service-connected disease, meaning any veteran who develops it is eligible for disability benefits regardless of when or where they served.