Muscle issues appear before memory loss

A new study has found that muscle weakness linked to Alzheimer's disease can occur years before memory loss begins, suggesting that the condition affects the body in ways not immediately tied to cognitive decline.

Motor symptoms originate in the nerves

Researchers from the University of Central Florida discovered that these early motor symptoms, such as slower walking and weaker grip, are not caused by the brain but instead arise directly in the peripheral nervous system, which controls muscles and sensory nerves outside the brain and spinal cord.

Long-term studies confirm the trend

Clinical research, including a twelve-year study by the UK Biobank, has shown that people who later develop dementia tend to walk more slowly and have weaker grips even before cognitive symptoms appear. Similar findings were reported by researchers at Tokyo Medical University, who noted slower nerve signal transmission in early Alzheimer's patients.

Scientists tested the source of the issue

To determine whether these motor issues came from brain damage or the peripheral nervous system, scientists used a human neuromuscular junction chip. This device mimics the connection between a motor neuron and a muscle cell, allowing researchers to study the system independently of the brain or spinal cord.

Alzheimer's neurons show early signs

The study used motor neurons derived from stem cells of people with a family history of Alzheimer's and connected them to healthy muscle cells. This setup revealed that the motor neurons themselves exhibited signs of dysfunction, supporting the idea that the peripheral nervous system plays a key role in early physical symptoms of the disease.