Introduction

Restless legs syndrome (RLS) is a sleep-related disorder characterized with abnormal sensation and desire to move the legs when resting [1]. It is a common cause of insomnia [2]. In 1995, the International Restless Legs Syndrome Study Group (IRLSSG) determined the standard criteria in order to make a correct diagnosis [3].

The RLS prevalence in the community was shown to be between 2.5 and 29 % in studies performed worldwide using different methods [4]. Prevalence in the two epidemiologic studies earlier conducted in Turkey were 3.2 [5] and 3.4 %, respectively [6]. There are no studies investigating the RLS prevalence in Ankara, capital city of Turkey.

Although a widespread disease, patients are misdiagnosed as symptoms are not fully known [7–10]. The complaints are usually considered to be associated with insomnia, stress, muscle cramps, arthritis, aging and even psychological diseases [11].

Materials and methods

We carried out this study between 2005 and 2007 in Ankara. Households in eight distinct districts of Ankara were included in the study. Help from the State Institute of Statistics of Turkish Republic was sought in order to determine the appropriate houses. The population labeling list that had been formed in year 2000 was used for sampling. The two-stage stratified cluster systematic random sampling method was the selected method. The first stage sampling unit comprised the blocks containing a mean of 100 houses, and the second stage sampling unit comprised the houses that had been systematically selected among the blocks. The sample was designed so as to estimate the prevalence in the Ankara province.

The total population of Ankara was 3,203,362, of which 2,420,973 (75 %) were above 15 years of age. The sample size was estimated as 600 houses using the random sampling in order to detect RLS with a 10 % error margin, 95 % confidence and 90 % power. The distribution of the Turkish population according to age groups was 31 % for 0–14 years of age, 63 % for 15–64 years, and 6 % for 65 years of age and above. According to this distribution and taking into consideration the fact that RLS is common among the elderly, taking individuals from 540 houses between the 15–64 age group and taking individuals from the remaining 60 houses from the 65 years and above age group was found to be appropriate.

Four university students not attending medical school were selected as interviewers and they were trained about the questionnaire they would apply and were sent to the selected houses after having obtained approval from the ethics committee. The subjects were given the questionnaire which was composed of four questions accepted as the minimal criteria for the diagnosis of RLS according to IRLSSG through face-to-face interviews: (1) the desire to move the limbs associated with paresthesias/dysesthesias, (2) motor restlessness, (3) symptoms are worse or exclusively present at rest (i.e., lying, sitting) with at least partial or temporary relief by activity, and (4) symptoms are worse at evening/night. In order to increase the number of subjects, all subjects over 15 years of age who lived in these houses and who had given consent were included in the study. The questionnaire forms were evaluated after all houses had been visited and the subjects who responded with ‘no’ to all four questions were not contacted again and were accepted not to have RLS. Subjects who responded with ‘yes’ to one or more questions were invited to the hospital through phone calls. Subjects who could come to the hospital were questioned by two neurologists working in the Department of Neurology, Ankara University Medical School; one was specialized in movement disorders (MCA) and the other was a third-year resident of Neurology (AO), and the subjects who met all four criteria defined by the IRLSSG were diagnosed with RLS. The RLS symptoms of the subjects who could not come to the hospital were questioned again in detail on the telephone.

Ten questions of the IRLSSG scoring [12] were asked in order to determine the disease severity in subjects who were diagnosed with RLS. Moreover, all patients were asked whether they had presented to a physician previously and the reason if they had not.

Statistical analysis

The SPSS version 10.0 was used. Descriptive statistics methods were used to estimate the prevalence values. The mean and standard deviation values were calculated for constant variables. Frequency tables were formed for categorical variables. We used independent sample t test to compare the means. A p value of <0.05 was regarded as significant.

Results

A total of 815 subjects from 600 houses were included in the study. The number of females was 509 (62.5 %) and the number of males was 306 (37.5 %). The mean age of the subjects was 43.3 ± 15.4 years (18–98), the mean ages of the females and the males were calculated as 43.0 ± 15.07 (18–95) and 43.7 ± 16.0 (18–98), respectively. The subjects were separated into four groups according to their ages (Table 1).

Table 1 Distribution of subjects according to age and gender
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Distribution of subjects according to their responses to the IRLSSG questionnaire was presented in Table 2. As 386 subjects responded ‘no’ to all questions, they were considered not to have RLS and were not contacted again. Four hundred and twenty-nine subjects who responded ‘yes’ to one or more questions were attempted to be questioned again and 109 of them could not be reached. Having contacted with 320 subjects who were questioned by two neurologists again, 39 subjects (32 females, 7 males) were diagnosed with RLS. The RLS prevalence in Ankara was estimated as 5.52 %; 7.44 % in females and 2.53 % in males. The mean age of RLS patients was 48.1 ± 12.9 years (27–73) and the mean ages of females and males were 46.3 ± 12.9 (27–73) and 56.0 ± 10.2 (42–72), respectively. No significant difference was found between the mean age of the two genders (p = 0.072).

Table 2 Distribution of subjects according to their responses to the IRLSSG questionnaire
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Distribution of RLS according to age and gender is presented in Table 3.

Table 3 Distribution of age and gender of patients who were found to have RLS
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Among RLS patients 16 out of 39 (41.0 % of the RLS patients) had answered ‘yes’ to either one, two and three questions of the questionnaire and 23 of the subjects with RLS (59.0 % of the RLS patients) responded ‘yes’ to all four questions as presented in Table 4. The number of subjects that could be reached was 108 out of 143 who answered ‘yes’ to all four questions. The percentage of RLS diagnosis was 21.3 % among the subjects who answered ‘yes’ to all four questions.

Table 4 The rate of the answers of the patients who were found to have RLS
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The mean scores according to the RLS study group severity scale were 18.7 (8–34) overall, and 16.6 (9–26) and 19.3 (8–34) for males and females, respectively. RLS was mild in 6 (16.7 %) patients, moderate in 16 (44.4 %) patients, severe in 13 (36.1 %) patients, and very severe in 1 (2.8 %) patient. The data of the RLS severity scale of three subjects could not be reached.

Patients who had received a definite diagnosis of RLS were contacted, by telephone calls, afterwards and asked whether they had gone to a doctor for their complaints and the reason if they had not presented to a doctor. Of the 39 patients who had been diagnosed with RLS, 9 had presented to a doctor, 26 had not, and 4 patients could not be reached. Fourteen patients had considered that this was a disease, but they could not go to a doctor; seven patients had gone to a doctor, but could not be diagnosed or treated with a wrong diagnosis (hypertension, diabetes, arthritis, varicose veins, insignificant complaints). Eight patients had not considered that this was a disease or did not care. Three patients had considered that the disease was related to another reason and did not present to a doctor. One patient had not presented to a doctor considering that he would not benefit from the visit. Two patients were diagnosed with RLS previously and had been treated.

Discussion

The prevalence of RLS is 5.52 % among individuals above 15 years of age in Ankara. There are two previous studies about the RLS prevalence performed on individuals above 18 years of age in Turkey, and they were also planned based on the IRLSSG criteria. The first study was performed in 2003 in Mersin, a city on the Mediterranean coast, and in this study, the prevalence was found to be 3.2 %. The subjects who had responded with ‘yes’ to all four questions asked by the interviewers had been included in the study, and those who did not have complaints during the recent one month had been excluded [5]. The RLS prevalence was calculated as 3.4 % in the study carried out in Kandira, a district of Kocaeli located on the Black Sea coast. Questionnaires were applied by three neurologists who lived in Kandira and the subjects who responded with ‘yes’ to all four criteria were accepted to have RLS [6]. Finally, the RLS prevalence was found to be 9.7 % among individuals above 40 years of age in the epidemiological study performed in Orhangazi-district of Bursa [13].

The prevalence was found to be between 8 and 12 % in USA and Europe in the previous studies [14–17]. The RLS prevalence is known to be lower in Asia. Prevalence is 0.1 % in Singapore, it is 1.5 % in Korea [18, 19]. Considering the geographical location of Turkey which is between the west and the east, finding a RLS prevalence between these values is interesting.

The RLS prevalence in Ankara is seen to be higher than the values found previously in Turkey. One reason for this may be the geographical location of the cities. Two cities which hosted the former studies are at the seaside (the altitude of Mersin is 5 m; the altitude of Kandira is 100 m). However, Ankara is at a much higher altitude than these two cities (the altitude of Ankara is 938 meters). The RLS prevalence was shown to be greater among individuals who live in areas with higher altitude [20].

Although there are currently many obscurities in RLS genetics [21], one of the major determinants of finding the RLS prevalence to be different from other studies in Turkey may be the genetic factors. We could only reach 320 subjects among positive responding 429 subjects (74.6 %). The inability to reach the data of 109 subjects may also have affected the prevalance values.

The RLS prevalence increases with age [6, 7]. A decline in RLS prevalence was detected in patients above 60–65 years of age [4, 15, 22]. While this may be associated with the scarcity of individuals in this age group, it may also be related to the coexistence of cardiovascular diseases, hypertension, diabetes mellitus and even stroke [23–26]. In other words, patients who have RLS die earlier [27]. Consistent with the previous reports, the prevalence increases with age first and declines at ages above 65 years or later in our study.

The RLS prevalence is about 1.5–2-fold greater in females compared to males [5, 8, 15, 28]. Hormonal differences between the genders, lower ferritin levels in females and differences between genders in perceiving and evaluating the symptoms may be the reasons for RLS being more frequent among women [27]. In our study, the prevalence was found as 7.44 % in females and 2.53 % in males (threefold more frequent in females).

Patients with mild complaints do not need pharmacological treatment [29]. Hence, the RLS patients that we aimed to treat were usually the moderate and severe ones. Symptoms were found to be moderate or severe in 60–80 % of RLS patients in previous studies [16, 27]. This rate was 83.3 % in our study.

The gold standard for the correct diagnosis of RLS is careful questioning the patients in detail by an experienced specialist [7]. Hening et al. [30] emphasized that the four questions were found to be sensitive, specific and reliable for diagnosing RLS when they were asked by sleep specialists on telephone encounter. They concluded that the results would be different if the questions had been asked by non-physician interviewers. In many previous studies, subjects who responded with ‘yes’ to all four questions according to the IRLSSG criteria were diagnosed with RLS, and the others were not questioned again. As it is too difficult to question all subjects by experienced specialists in epidemiologic studies, pollsters were requested for this task. In our study, we questioned again the ones who responded to even one question with ‘yes’ again, and saw that some of them were diagnosed with RLS (41.0 % of those who were diagnosed with RLS). We diagnosed only 23 subjects with RLS when we reached 108 out of 143 subjects who had responded with ‘yes’ to all four questions (21.3 %). In conclusion, not only directly asking these four questions, but also properly questioning the criteria and additional questions that could be beneficial for diagnosis, neurological examination, and experience and knowledge of the neurologist on this issue are necessary for diagnosing RLS.

Hening et al. [14] showed in their study carried out in primary care centers in Europe and USA that the diagnosis of RLS could not be made. Many patients believe that RLS is an insignificant disease, complaints are psychogenic or there is no treatment for the disease. Because of this way of thinking, making a correct diagnosis becomes difficult [31]. In our study, only nine of the patients diagnosed with RLS had gone to a doctor previously, and only two were diagnosed correctly. As a result, it seems that neither the patients nor the doctors are familiar with RLS. The importance of this subject should be given to postgraduate education, especially in primary care services; at least doctors should be taught that patients who present with these complaints should be referred to a neurologist.

Conclusions

The prevalence of RLS in Ankara is 5.52 %. The four question criteria when applied by non-physician pollsters may not be predictive of the diagnosis of RLS. Additionally, number of experienced neurologists and family physicians should be increased in order to diagnose RLS correctly in our country.