Restless Leg Syndrome and Insomnia (Science-Based Summary)

As someone who had restless leg syndrome and sleep trouble in the past, I’ve always seen a connection between the two.

But personal stories don’t mean much.

Instead, I’m going to walk you through research that shows just how restless leg syndrome is related to insomnia, and how it’s typically treated.

Does Restless Leg Syndrome Cause Insomnia?

The research we’re about to go over shows that there is a correlation between insomnia and restless leg syndrome (RLS).

And since it seems unlikely for insomnia to cause RLS (it’s not a known side effect of insomnia), it’s likely that RLS can indeed cause insomnia for some people.

One thing to keep in mind is that most RLS studies look at it in patients with at least 1 other condition, so it doesn’t necessarily have the same impact as it does in the general population that is mostly healthy.

Several studies have looked at the effect of RLS in patients on dialysis, as RLS occurs in about 14% of them (1). One study found:

RLS patients were twice as likely to have significant insomnia as patients without RLS

Furthermore, RLS was associated with poor sleep quality overall, and impaired quality of life.

A questionnaire sent randomly to 1962 Swedish residents found that infrequent RLS is NOT associated with an increased risk of insomnia, but frequent RLS makes someone 3.5 times more likely to develop insomnia (2).

As you can see in the table, people with frequent RLS struggled both with falling asleep and waking up more often. They were also more likely to have anxiety and depression, which are both risk factors of insomnia.

Because of the link between mental health and insomnia, another team of researchers studied 203 psychiatric patients in a hospital (3). They found that:

67.4% were found to have insomnia and 14.3% were found to have RLS. The severity of insomnia was found to be associated with the presence of RLS, depressive and anxious symptomatology, suicidal ideation, use of selective serotonin reuptake inhibitors, and use of benzodiazepines.

In other words, severe RLS was found in patients with the worst insomnia and overall mental health.

It’s also interesting to note that about 1 in 4 patients with insomnia had RLS, reinforcing that it’s fairly common.

SummaryInfrequent and mild RLS is unlikely to cause insomnia. However, people with frequent or severe RLS have a much greater risk of developing insomnia.

What Causes Restless Leg Syndrome?

In order to treat something, you need to understand it.

While there are still some mysteries about RLS, we know that it’s a disorder of the central nervous system and often a result of dopaminergic dysfunction.

The main causes are:

• Iron deficiency (in the CNS) - Sometimes serum ferritin levels (which is measured for iron content) is normal, but the CNS can be low in iron, which appears to be a common cause of RLS (4).
• Dopaminergic abnormality - Research shows that if dopamine is not being controlled correctly, it can cause RLS (4).
• Genetic components - The specific genes haven’t all been identified, but it’s clear that genetics often play a role (5).
• Anemia (and B12 deficiency) - While not as common as the above causes, there is some evidence linking anemia to RLS. Anemia is usually caused by a lack of iron, but can be caused by a vitamin B12 deficiency as well in some cases.

And while it’s not a specific cause, there’s a clear link between age and RLS in both genders (2).

Other Potential Causes of RLS

As mentioned, there’s still more to be learned about RLS.

Something that researchers have noticed is that RLS is particularly common in pregnancy, particularly in the third trimester along with insomnia.

And while the usual suspects like iron deficiency often play a role, magnesium seems to play a major role in this specific situation.

One case study reported that magnesium supplementation completely alleviated RLS symptoms in a woman in her third trimester (6).

Another novel study was able to show that (7):

Magnesium and zinc deficiency may play a role in the etiology of RLS during pregnancy

So while these likely aren’t common causes in the general population with RLS, there’s more for researchers to explore still.

How is RLS and Insomnia Treated

When it comes to insomnia, doctors typically prescribe cognitive behavioral therapy modified for insomnia (CBT-i) to start with.

But with the causes we saw above, further treatment is likely necessary to treat underlying causes (other than genetics which there’s not much you can do about).

Currently, the most common treatments for frequent or severe RLS include:

• Dopaminergic drugs - These are fairly effective for most people with RLS, however, they do cause side effects like nausea or hypotension in some, which may require even more medication (8). Additionally, it’s possible to develop a tolerance to these drugs.
• Iron therapy - If iron stores appear low, iron-replacement therapy (i.e. supplementation) is the obvious treatment that is usually effective (9).

As noted, magnesium or zinc supplements might be recommended if stores of either are low, but they aren’t the most common causes other than during pregnancy. It’s still not clear if magnesium helps relieve RLS or not in general (10,11).

Finally, for less severe cases, massages or temperature baths can help relieve symptoms a bit for those that would like to try and avoid a pharmacological approach (9).

Can RLS Be Measured?

When you see a doctor for RLS and sleep issues, they will typically rule out obvious causes with a blood test.

A potential next step is to have you complete a sleep study.

Many things can be measured, including periodic limb movements during sleep (PLMS) by using the PLMS index.

Summary: Restless Leg Syndrome and Insomnia

There’s quite a bit of evidence showing that restless leg syndrome is a common trigger for insomnia.

Mild RLS doesn’t raise the risk of insomnia much, but frequent RLS puts someone at much greater risk of insomnia (about 3.5 times as likely).

Most cases of RLS are caused by either iron deficiency in the CNS, or a dopaminergic abnormality. These can be treated with iron therapy and drugs that target dopaminergic regulation under the supervision of a doctor.

Finally, there appear to be other specific situations where RLS might be caused by something else, so more research still needs to be done to understand the condition better.

References

1. Restless legs syndrome, insomnia and quality of life in patients on maintenance dialysis
2. Restless legs syndrome and its relationship with insomnia symptoms and daytime distress
3. Insomnia in hospitalized psychiatric patients
4. The role of iron in restless legs syndrome
5. Considering the causes of RLS
6. Intravenous Magnesium Sulfate May Relieve Restless Legs Syndrome in Pregnancy
7. Zinc and Magnesium Levels of Pregnant Women with Restless Leg Syndrome and Their Relationship with Anxiety
8. Restless legs syndrome and its treatment by dopamine agonists
9. Restless Legs Syndrome: Contemporary Diagnosis and Treatment
10. Magnesium Therapy for Periodic Leg Movements-related Insomnia and Restless Legs Syndrome
11. Magnesium supplementation for the treatment of restless legs syndrome and periodic limb movement disorder: A systematic review