Review: Muscle Loss May Link Poor Sleep to Alzheimer's Risk

Sleep often becomes lighter and more broken with age. That is thought to be one possible reason the brain grows more vulnerable to Alzheimer's. Less deep sleep and frequent waking may help harmful proteins such as amyloid and tau build up. One researcher now argues that the muscles belong in this picture too.

In his review, he brings together work on sleep, aging and metabolism. His idea: age-related muscle loss, muscle loss combined with obesity, and insulin resistance may disturb sleep. Insulin resistance means the body's cells respond poorly to insulin. Together with low-level inflammation, these conditions might let broken sleep harm the brain more easily. As a possible go-between he points to irisin, a messenger from muscle linked to a growth factor that supports nerve cells.

This is a proposed model, not a new measurement. The author himself stresses that direct evidence for irisin playing a causal role in human sleep is lacking. He sets out predictions that experiments can test. In time, the model might help combine better sleep, strength training and metabolic treatment.