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Restless legs

Study
Results
PLMD
RLS
Comment

“Oh sleep! It is a gentle thing” is what the Ancient Mariner thought, and few would argue with that. The trouble is getting enough of it. For those of us blessed with the ability to sleep well and long, one interrupted night comes as a bit of a shock. To imagine what it is like for those whose sleep is frequently interrupted is very difficult. Which is perhaps why a Bandolier reader asked about restless leg syndrome, whether it is real, how common it is, and how to cure it.

Bandolier found no simple answer to the third part of the question, but a good source of information about the first two parts in a large prevalence study that examined both restless leg syndrome (RLS), and the related periodic limb movement disorder (PLMD) [1]. The answer is that about 1 person in 20 has RLS, about 1 in 25 PLMD, and an unlucky 1 in 100 has both.

Study

The study was conducted in five European countries (UK, Germany, Italy, Portugal, and Spain) in the mid-1990s. The target population was adults aged 15 or over living at home. A random selection of telephone numbers was drawn after geographical stratification, and a household member selected by age and sex.

Expert system software was used to administer questionnaires in a formulated and consistent way. The software had been specifically designed and tested to evaluate sleep disorders, and to use key diagnostic criteria administered in an exact way. The software also prompted questions about sociodemographic information, medical history, use of alcohol, tobacco and coffee, medicine use, physical activity, stress, and mental disorder.

The definitions used for PLMD and RLS were those of the International Classification of Sleep Disorders.

Periodic limb movement disorder:

Restless leg syndrome

Results

The sample was 18,980 people, with just over half women, and with an age range of 15 to 100 years. Four participated out of every five people asked. PLMD was higher in women than men, but RLS was higher in men than in women (Figure 1). About one in five people who had one complaint also had the other. Overall, about 1 person in 25 has PLMD, about 1 in 20 RLS, and an unlucky 1 in 100 has both.


Figure 1: PLMD and RLS in women and men




PLMD was constant across ages, but RLS increased with age (Figure 2). Compared with the youngest age group, there were statistically increased rates of RLS in people older than 40 years. Associations with medical conditions, demographics and lifestyle were also examined for PLMD and RLS.


Figure 2: PLMD and RLS by age




PLMD

People with PLMD were more likely to have musculoskeletal disorders (18%), heart disease (5%), diabetes (2%), or particularly have a mental disorder (34%). They were more likely to take anxiolytics (5%) or hypnotics (10%). Sleep apnoea syndrome (9%) was also common.

In terms of lifestyle, drinking more than six cups of coffee a day was more frequent (22%) in people with PLMD, and 29% had high life stress.

RLS

People with RLS were more likely to have high blood pressure (22%), musculoskeletal disorders (13%), heart disease (7%), diabetes (2%), or a mental disorder (16%). They were more likely to take anxiolytics (5%) or hypnotics (10%).

Coffee drinking was less common in people with RLS, and 41% drank no coffee at all.

Comment

A few interesting lessons. First was that for something really quite common, there were few large studies of prevalence based on whole populations and with clearly defined diagnostic criteria. Second is the fact that these conditions are quite common. They affect about 1 in 15 of us.

Whether we can make much of the associations is another matter. One that was interesting was that most of the people with PLMD or RLS had some physical or mental medical condition, roughly 7 out of 10. Whether it is possible to make much of the lifestyle associations is less clear. Some might try to make something out of associations with coffee. But people with RLS tended to drink less coffee. Should they be encouraged to drink more, or have people with RLS have found that coffee drinking makes things worse, or have they been told that it does, so have reduced coffee intake?

The next step is treatment. That is less easy. Bandolier found about 20 or so randomised trials, but no systematic reviews, on a quick search. Time for someone to do some literature synthesis, perhaps.

References:

  1. MM Ohayon, T Roth. Prevalence of restless leg syndrome and periodic limb movement disorder in the general population. Journal of Psychosomatic Research 2002 53: 547-554.

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