A study has found that restless legs syndrome, in which legs tingle and ache nightly and make sleep difficult, is closely associated with decreases in muscle mass in men.

A research team led by Professor Hee-won Bae of the Department of Neurology at Inje University Ilsan Paik Hospital and Professor Eun-yeon Joo of the Department of Neurology at Samsung Medical Center analyzed the relationships between various indicators that reflect body composition and the occurrence of restless legs syndrome, and announced on the 2nd that they published the results in the international journal ‘Frontiers in Neurology’. The team analyzed together the data from body composition tests and polysomnography conducted on 5,752 adults.

Restless legs syndrome is a neurological disorder in which, mainly during evening or nighttime rest, unpleasant abnormal sensations that feel like insects crawling on the legs occur, or pain such as tingling and aching appears. Because there is an urge to keep moving the legs to ease these sensations, persistent symptoms can lead to chronic insomnia and a decline in quality of life.

In the results, overall prevalence was higher in women (6.6%) than in men (2.9%). However, the association with muscle mass was clearly observed only in men. In particular, men with sarcopenia had an 8.7% rate of accompanying restless legs syndrome, about 2.7 times higher than in those without it (3.2%). Periodic limb movements during sleep were also about 1.7 times more frequent.

Across various indicators of muscle mass, the association with the risk of restless legs syndrome was observed consistently. When the skeletal muscle index (SMI), which shows how much muscle mass there is relative to height, was low, the risk of restless legs syndrome rose by 6.5%, and when the fat-free mass index (FFMI), which represents the amounts of muscle, bone, and water, was low, the risk increased by 2.5%.

Conversely, men with sufficient muscle mass tended to have a significantly lower risk of restless legs syndrome, and in particular, when the skeletal muscle index was high, the risk of the disorder was about 20% lower. This suggests that even at the same body weight, risk increases when the proportion of muscle is low and body fat is high, whereas sufficient muscle mass may confer a protective effect.

Investigating how muscle loss may influence the development of restless legs syndrome, the researchers considered factors such as reduced capacity to deliver oxygen to peripheral tissues, decreased levels of anti-inflammatory substances derived from muscle (myokines), and the possibility of changes in the dopaminergic system due to increased oxidative stress. In men, it may also be related to a complex physiological cycle in which sleep deprivation leads to decreases in the male hormone testosterone and to muscle loss, which in turn connects back to poorer sleep quality in a vicious cycle.

Professor Hee-won Bae said, “This study shows that restless legs syndrome can be closely linked to muscle status beyond being a simple neurological symptom,” and added, “In men in particular, because a decrease in muscle mass may act as an important risk factor, active management that combines resistance training and aerobic exercise may help.”