Evidence in practice — number 4: Restless legs

Clinical question: How common is restless legs syndrome in primary care?

The evidence: Restless legs syndrome symptoms in primary care. A prevalence study. Arch Intern Med 2003; 163: 2323-2329.1

Background: Patients with restless legs syndrome suffer from a range of sensory and motor symptoms affecting their legs during rest and/or while asleep. The sensory disturbance encompasses such symptoms as burning, cramps, paraesthesia, or weakness. In general, these symptoms can be temporarily relieved by moving the legs. There is no diagnostic test for the syndrome but to be categorised as having restless legs syndrome four criteria must be satisfied:1

1. The patient must have an urge to move the legs, usually accompanied by an unpleasant sensation in the legs

2. Restless legs syndrome symptoms must be aggravated by rest

3. Restless legs syndrome symptoms must be alleviated by movement and, in particular, walking

4. Restless legs syndrome symptoms must be worse in the evening or night (either currently or when the condition first started).

Over the years many patients with restless legs syndrome have had their symptoms labelled as trivial or ‘neurotic’.1^,2 This is unfortunate as the condition can cause considerable distress due to the associated sleep disturbance. Moreover, there are a range of treatments now available to help manage the condition.2 There is also a suggestion that, as GPs, we fail to recognise the condition as we have a distorted perception of its prevalence among the groups of patients we are likely to encounter.1^,2

Study design: This was a cross-sectional prevalence study conducted in the context of a three-doctor primary care practice in rural Idaho. Over the course of 1 year every patient aged over 18 years with an appointment at the clinic was asked to complete a ‘Restless Legs Syndrome Questionnaire’ (RLSQ). Patients who were not approached during their clinic appointment were subsequently mailed a questionnaire. For those patients filling in the RLSQ at the clinic, a researcher was available to provide assistance with interpretation or completion.

Outcome measure: In comparison with expert clinical diagnoses for patients attending a sleep disorder clinic, the RLSQ had previously been assessed as having a sensitivity of 92% and a specificity of 95%.

Results: Over the course of 1 year 2696 patients had clinic appointments and, of these, 1905 completed the RLSQ at the clinic and 194 by post. Overall 24% of patients could be classified as having restless legs syndrome according to all the four key criteria. The prevalence increased with age and was greater amongst women than men.

Commentary: When assessing the results from any prevalence study it is important to consider whether the results are trustworthy or have arisen as a result of bias/confounding.

In terms of the population studied, it is likely that there was some selection operating between those that participated and those that did not. Non-participants were more likely to be male and also tended to be slightly older (selection bias). Furthermore, there may be differences between those that completed the questionnaire by post or independently and those who sought ‘guidance’ from the researcher (that is, observation and interviewer bias).

There are often concerns about the use of instruments (for example, the RLSQ) that have been validated in a secondary care setting. It would clearly have been better if the instrument had been validated in a primary care population but, on the other hand, the questionnaire has clearly undergone some kind of validity assessment which, sadly, is frequently not the case in many surveys conducted in primary care populations.

Confounding occurs where there is a third factor associated with the diagnosis of restless legs syndrome that could also, and independently, cause patients to make clinic appointments, thereby artificially enhancing the true prevalence among clinic consulters. A possible source of confounding relates to the observation that individuals with chronic diseases have higher consultation rates and, independently of this, have a greater tendency towards restless legs syndrome.

Overall, I would suggest that the results are important, but the prevalence is probably slightly overestimated due to the effects of bias and confounding. It is interesting to note that other population-based studies have placed the prevalence between 9% and 15%.2

In applying the results of this study to UK primary care, a further judgement needs to be made as to how similar the US clinical attendees would be to patients who consult UK GPs. According to Jones and Menzies, the average three-partner practice in this country would see 8400 patients for generalised conditions per annum;3 approximately three times the number seen in the US situation. It would also be interesting to know whether the US survey was restricted solely to new clinic appointments for unrelated problems. Clearly, some patients may have been follow-up visits and some may have been consulting specifically about restless legs-type symptoms.

However, the overall message is that we should be more alert to restless legs syndrome; the prevalence is certainly much higher than many of us would expect.

The bottom line: Restless legs syndrome is not an uncommon problem among patients who are likely to consult us in routine practice; it may be present in up to a fifth of our patients. We should endeavour to be more alert to the diagnosis.