Restless legs syndrome

What it is

Restless legs syndrome is defined by an urge to move the legs, usually with uncomfortable sensations, that begins or worsens at rest, is relieved by movement, and is worse in the evening or at night. The relief with movement is the diagnostic feature.

The mechanism involves dopamine signalling and, importantly, iron handling within the brain. Brain iron can be low even when blood tests look normal, which is why ferritin - the iron store measurement - is the test that matters and why a level considered normal for general purposes may still be too low here.

What it feels like

• A crawling, tugging or fizzing sensation deep in the legs, hard to describe
• An overwhelming urge to move them, relieved for a few moments by doing so
• Worst sitting still in the evening and when getting into bed
• Severely disrupted sleep, both getting off and staying asleep
• Sometimes involuntary leg jerks during sleep, reported by a partner

What causes it

Most people have more than one of these at once, and they feed each other. Read the list looking for the two or three that sound like your week rather than for the one true answer — the ones that describe you are the ones worth acting on.

Low brain iron

Iron is a cofactor for dopamine production, and low brain iron is a central mechanism. Serum ferritin below about 75 micrograms per litre is enough to contribute even though it would be reported as normal for other purposes.

Dopaminergic dysfunction

The dopamine system in the brain regulates movement, and its dysfunction produces the urge and the sensations. This is why dopamine drugs work - and why they eventually cause augmentation.

Iron deficiency from any cause

Heavy periods, blood donation, coeliac disease, gastrointestinal bleeding. Restless legs can be the presenting symptom of an iron deficiency with a cause that needs finding.

Pregnancy

Very common, particularly in the third trimester, driven by increased iron demand and hormonal change. It usually resolves after delivery.

Chronic kidney disease

Restless legs is extremely common in people on dialysis, related to both iron handling and uraemia.

Medications

Antihistamines, many antidepressants including SSRIs and mirtazapine, some antipsychotics and anti-nausea drugs all commonly worsen it. This is one of the most useful things to review.

Genetics

Strongly familial, with several identified genetic associations. Around half of people with the primary form have an affected relative.

Caffeine, alcohol and nicotine

All three worsen symptoms in most people, and evening caffeine in particular is a common and easily removed contributor.

Peripheral neuropathy

Nerve damage, most often from diabetes, is associated with secondary restless legs and needs identifying because the treatment differs.

Augmentation from dopamine drugs

Long-term dopamine agonists cause symptoms to start earlier in the day, spread to the arms and become more severe. It is a common and serious complication that is often mistaken for the disease worsening.

Who tends to get it

• Anyone with low iron stores, which is the most important treatable cause
• Women, particularly during pregnancy
• People with chronic kidney disease
• Anyone taking antihistamines, SSRIs or mirtazapine
• People with a family history, which is common

What makes it worse, and what settles it

The qFIT routine for this

Ready-made routineLeg Cramp Relief

qFIT already has this one built. It runs massage first, then stretching, then strength — the order that works on a body that is already sore — and every activity in it carries the reason it is there.

The button below opens your Checklist with this routine already selected, so instead of your whole list you land on just its Categories, Targets and Exercises, each with its checkbox, ready to tick as you work through them.

Have more than one problem? Tick yours under My Problems on My Profile and your Checklist's Routine list gains Recommended for my problems — every routine for the problems you picked, merged into one. Your picks stay private; that filter is the only thing they feed.

Get it checked if…

Sudden onset or one-sided symptoms are not RLS; check iron studies and medications

And whatever the body part: chest pain or unusual breathlessness on exertion; a fever alongside the pain; unexplained weight loss; pain that is constant and unrelated to how you move; new numbness, weakness or loss of bladder or bowel control; or one calf that is swollen, warm and painful. Any of those, stop and get assessed.

How it usually goes

Where iron deficiency is the driver, replacement can produce substantial improvement over one to three months, and it is the intervention most often missed. Regular exercise reduces severity measurably. Medication is effective for severe cases and should be prescribed by someone who understands augmentation, since the long-term management is genuinely different from starting treatment. Symptoms that begin earlier in the day or spread to the arms on treatment should prompt a review rather than a dose increase.

Prevalence basis: Sleep medicine epidemiology

Others the same routine covers

These share the Leg Cramp Relief routine, so the work is the same. If one of them also sounds like you, that is a reason to expect more from it, not less.

This is general information, not a diagnosis, and it cannot examine you. If it matches you, use it to ask better questions of a clinician rather than to replace one.