(Reuters Health) - Even though the neurologic disorder known as Lou Gehrig’s disease has long been thought to ravage the body while leaving the mind untouched, a new study suggests that the condition may also affect thinking skills and behavior.

Amyotrophic lateral sclerosis (ALS) is commonly known as Lou Gehrig’s disease after the New York Yankees first baseman who retired after developing this condition. The rare neurologic disease mainly affects the nerve cells responsible for controlling voluntary muscle movement such as walking or talking. It has no cure, and gets worse over time until it eventually leads to death, most often from respiratory failure.

For the study, researchers analyzed thinking skills tests and caregiver questionnaires about behavioral symptoms like apathy and sympathy for 161 people with ALS. They also studied 80 individuals without ALS.

People with ALS did worse on all of the thinking tests except those involving visual-spatial skills, which aren’t thought to be impacted by ALS, researchers report in Neurology.

Patients with ALS also had more frequent and severe cognitive and behavioral deficits as their disease progressed.

“This is the first study which has shown that cognition and behavior is affected in the earliest stages of the disease and that patients are increasingly impaired in the later stages of the disease,” said senior study author Sharon Abrahams, a neurology researcher at the University of Edinburgh in the U.K.

“By the end stage of the disease only a very small proportion of patients (20 percent) are free from cognitive or behavior change,” Abrahams said by email.

The study findings suggest that all patients with ALS should be screened for behavioral and cognitive decline as their illness progresses, Abrahams advised.

Researchers defined the progression of ALS based on how many regions of the body were affected by looking at movement in the upper limbs; lower limbs; bulbar region that includes muscles involved in speech and swallowing; and breathing and eating. Patients with the most advanced ALS typically require interventions like breathing machines or feeding tubes.

Overall, 29 percent of the people with ALS had problems with their thinking skills, with the most common problems occurring on the test of verbal fluency, where people list as many items as they can that start with a certain letter, and the test of executive functioning, such as paying attention to two things at once.

Of the 149 people with ALS with information on behavioral symptoms, 45 percent had no problems, 22 percent had one symptom, 14 percent had two symptoms and 20 percent had three or more symptoms.

Apathy was the most common symptom, at 31 percent. Loss of sympathy or empathy affected 28 percent and changes in eating behaviors affected 25 percent.

At the early stages of ALS, roughly one in five people had thinking problems or behavior issues. By the most advanced stage of ALS, about 40 percent had thinking problems and 65 percent had behavioral issues.

Difficulty with swallowing appeared independently connected to the risk of thinking and behavior problems even when people were still in the earlier stages of ALS, the study also found.

The study wasn’t a controlled experiment designed to prove whether or how ALS might directly cause cognitive or behavioral problems. It also only looked at patients at one point in time, so researchers were not able to track patients to see how any thinking or behavioral changes might change over time as ALS progressed.

Still, the results should help more doctors recognize the potential for ALS to affect the mind, said Paul Wicks, author of an accompanying editorial and vice president of innovation at PatientsLikeMe, a health data company in Cambridge, Massachusetts.

“Without knowing that this can be a part of the condition, patients and caregivers can sometimes blame themselves, worry that they’ve done something wrong, or are failing in some way - that’s not the case,” Wicks said by email. “This study should be a wakeup call to the field that it’s time we own this issue so we can address it head on.”

SOURCE: bit.ly/2x5IuBM Neurology, online September 12, 2018.