Can ALS be caused by traumatic brain injury?

Amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) is a neurologic disease that damages nerve cells in the spinal cord and brain, causing widespread muscle wasting and weakness. It strikes without warning, usually beginning between the ages of 55 and 75. As it worsens, ALS disables a person’s ability to move, speak, eat, or breathe. Although two FDA-approved medications can modestly slow its progress, death generally occurs within three to five years of diagnosis.

Decades of research have failed to come up with a definite cause. However, one new study supports a link between playing professional football and ALS.

Why is ALS called Lou Gehrig’s disease?

Since it was first described in the 19th century, much about ALS has remained mysterious. It’s quite rare, affecting about two in 100,000 people. It might have remained a disease you’d never heard of if not for Lou Gehrig, the Hall-of-Fame baseball player who played for the New York Yankees in the 1920s and 1930s. He developed ALS at age 36 and died of the disease two years later. Since then, ALS has often been called Lou Gehrig’s disease.

In recent years, widespread social media campaigns, such as the Ice Bucket Challenge, have raised awareness and funding for ALS research.

Searching for a cause of ALS

Some research suggests that risk factors for ALS include:

New research links playing professional football with ALS

A study published in JAMA Network Open might help us better understand the cause of at least some cases of ALS. It strongly suggests that playing professional football may be a risk factor for the disease.

Importantly, this study did not assess why there might be a relationship between ALS and playing professional football. The study authors speculate that traumatic brain injury might be to blame.

How certain are these findings?

This was an observational study. Observational research can identify a link between a possible risk factor (in this case, playing in the NFL) and a disease (ALS). However, it cannot prove that the risk factor caused the disease.

(Robert H. Shmerling, M.D., is a senior faculty editor at Harvard Health Publishing.)