Neurol Sci DOI 10.1007/s10072-015-2206-1
ORIGINAL ARTICLE
An epidemiologic study of restless legs syndrome among Chinese children and adolescents Rui Xue1 • Gangqiong Liu2 • Shengli Ma3 • Jing Yang4 • Ling Li2
Received: 4 February 2015 / Accepted: 1 April 2015 Ó Springer-Verlag Italia 2015
Abstract To determine the prevalence of restless legs syndrome (RLS) in Chinese children and adolescents as well as the impact of the disorder on 8–11 and 12–17 years old. This population-based study was conducted in five primary schools and seven high schools, which were randomly selected in Henan province, China. A total of 6792 students aged 8–17 years old were given a questionnaire that included the adult diagnostic criteria of RLS proposed by the International Restless Legs Study Group. Subjects who answered ‘‘yes’’ to all four questions were selected for a face-to-face interview to confirm RLS diagnosis. Individuals with definite RLS were then administered another questionnaire to survey RLS symptoms and perceived consequences. The prevalence of definite RLS in Chinese children and adolescents was 2.2 % (141/6437), with a prevalence of 1.8 % in the 8–11 years old age group and 2.4 % in the 12–17 years old age group. RLS was found to be more prevalent in females (2.7 %) than in males (1.7 %) (P = 0.008), and the prevalence of RLS was determined to & Rui Xue [email protected] 1
Department of Urology, Institute of Clinic Medicine, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
2
Department of Cardiology, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
3
Department of Emergency, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
4
Department of Neurology, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
increase with age. Sleep disturbance was the most common symptom of RLS in children and adolescents. Various consequences were attributed to RLS, with participants reporting that they dreaded the arrival of evening/night most frequently, followed by the description that RLS had a negative impact on mood. These data suggest that RLS is prevalent in Chinese children and adolescents, and that those affected by this disorder suffer from disruptions to sleep and daytime function. Keywords Restless legs syndrome Children Adolescents Prevalence Chinese
Introduction Restless legs syndrome (RLS) is a common sensorimotor disorder, which is characterized by an irresistible urge to move the legs that is typically accompanied by uncomfortable and unpleasant sensations. The diagnostic criteria of RLS, which were revised by the International Restless Legs Syndrome Study Group (IRLSSG) in 2003 [1] have been adopted extensively throughout the world. According to these criteria, adults and adolescents aged 12 or older must display four essential characteristics for a definite diagnosis of RLS. On the other hand, a diagnosis of possible or probable RLS can be given to individuals who do not exhibit all four characteristics [1]. The pediatric criteria for RLS diagnosis in children and individuals with cognitive impairment have evolved out of the adult RLS criteria, with some supportive criteria proposed. Thus, under the pediatric RLS criteria, it is more difficult to diagnose a child with a definitive RLS diagnosis. It has been reported that RLS can have adverse effects on an individual’s sleep [2], mood [3], cognitive function
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Neurol Sci
[4], and quality life [5, 6]. While the pathophysiology of RLS is still unknown, some potential factors may affect the occurrence of the disorder. For example, certain conditions or diseases, such as pregnancy, anemia, and uremia, have been found to be related to RLS in adults. In children and adolescents, RLS more frequently occurs in individuals with attention-deficit hyperactivity disorder [7], periodic legs movements in sleep (PLMS) [8, 9], migraine [10], kidney disease [11], and/or growing pains [12]. Over the last 20 years, the occurrence of RLS in adults has been increasingly recognized. For example, several epidemiological surveys have found that 5.5–11 % of adults in Western countries [13–16] have RLS, while the rates in Asian countries are lower [17, 18]. However, only a few studies on the prevalence of RLS in adolescents and children have been conducted. A Peds REST study, which was conducted in the United States (US) and the United Kingdom, revealed the prevalence of definite RLS in children aged 8–11 and 12–17 was 1.9 and 2.0 %, respectively [19]. Another study conducted in Turkey, reported the prevalence of definite RLS to be 1.7 % in children aged 10–12 and 3.2 % in those aged 13–19 [20]. These studies indicate that, although the prevalence of RLS in children is relatively lower than that in adults, RLS is not a rare condition in childhood. Taken together, we feel that epidemiological studies on RLS in the pediatric population are still very limited. Thus, to contribute to the pediatric perspective of RLS, the aims of the current study were to determine the prevalence of definite RLS in Chinese children and adolescents as well as to investigate conditions that correlate with RLS in this population.
to give students a questionnaire that was designed to investigate the essential diagnostic criteria of RLS for children and adolescents, which were proposed by the IRLSSG in 2003 [1]. Participants were stratified by age into two groups: 8–11 and 12–17 years old. Adult RLS criteria were used in questionnaires administered to adolescents aged 12 or older, while pediatric criteria were used for participants aged 11 years or younger (Table 1). After questionnaires were distributed, the aim and procedure of the study were clearly explained, and students were asked to complete their surveys at home. For participants in the younger age group, parents were asked to complete the questionnaire with the child present for the section that contained questions about leg feelings. All questionnaires were collected 3 days after they were sent out. No matter what age group the students belonged to, participants that answered ‘‘yes’’ to questions 1, 2, 3, and 4 were interviewed by a senior child neurologist (J. Y.) to determine whether they were really suffering from RLS or whether their questionnaire results were just a false positive. Subjects who were diagnosed as having definite RLS were required to fill out an additional questionnaire aimed to survey the following items: frequency of RLS (\1 time per month; 1–3 times per month; 1–2 times per week; 3–6 times per week; C1 time per day), impact of symptoms on sleep (difficulty falling asleep, interrupted sleep, poor sleep quality, excessive daytime sleep, insufficient hours of sleep), impact of symptoms on daytime function (inability to concentrate in class), health status (exhaustion, fatigue), study (poor academic performance), mood (irritability, dreading the arrival of evening/night), and other aspects affected by RLS (displayed in Table 2 as ‘‘other effect not listed’’).
Materials and methods Definition of RLS Population From September 2014 to January 2015, a cross-sectional epidemiological survey of RLS among Chinese children and adolescents was carried out in Henan Province, which is located in the central-east part of China. The study took place in five primary schools and seven high schools. All study participants were randomly selected, and a total of 6437 students ranging in age from 8 to 17 years were included in this study. All participants and their parents were informed about the nature of the research and provided us with written consent that was approved by the local ethics committee (No. CHN287/14). Procedures After obtaining permission from the authorities of each school, a trained researcher visited participating classrooms
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In this study, children aged 11 and younger were diagnosed as having definite RLS based on criteria set forth by the IRLSSG for pediatric RLS. Criteria for pediatric RLS proposes the following items in addition to the four essential adult RLS criteria: a consistent description of leg discomfort in a child’s own words with the presence of unpleasant sensations, or an answer of ‘‘yes’’ to both ‘‘Did you experience sleep disturbance’’ and ‘‘Do you have a biological parent or sibling with definite RLS’’. According to the IRLSSG diagnostic criteria, a third supportive criterion (a PLMS index of C5/h on polysomnography) should also be used as an item for diagnosis of RLS. However, this criterion was disregarded in our study because its use is inconvenient in an epidemiological survey, and it is more commonly used in clinical studies. For adolescents aged 12 or over, adult diagnostic criteria were used.
Neurol Sci
0.85 (0.63–1.08) 55
Of the 6792 questionnaires distributed, 6437 (94.8 %) were returned with valid answers that were entered into the final analysis. A total of 152 children and adolescents met all four essential RLS criteria in our questionnaire. Our interview confirmed the diagnosis of definite RLS in 2.2 % of these students (141) (Table 1). The prevalence rate across different age groups was 1.8 % for ages 8–11 years and 2.4 % for ages 12–17 years; however, there was no significant difference between the two groups (P = 0.115). Of these, 4.4 % (2/45) of participants in the younger age group and 5.2 % (5/96) in the older age group reported that the frequency of RLS was \1 time per month, corresponding with prevalence estimates of 0.08 and 0.13 %, respectively. On the other hand, 40 % (18/45) of children in the younger age group and 38.5 % (37/96) of adolescents reported an RLS frequency of C1 times per day, corresponding with prevalence estimates of 0.73 and 0.93 %, respectively. An increasing trend of prevalence from mild RLS to moderate or severe RLS was found from these data (Table 1). In the total sample, the prevalence of definite RLS was 1.7 % (61/3497) in males and 2.7 % (80/2940) in females, and this difference was statistically significant (P = 0.008). The distribution of the male:female ratio by age group demonstrated a prominent gender difference in the 8–1 years old group. However, for participants that reported an RLS frequency of at least three times per week, no significant gender differences were found in either age group. See Table 2 for a detailed analysis of gender data for the definite RLS groups.
2.19 (1.83–2.55) 141 6437
2465 3972 8–11 12–17
Total
CI confidence interval
1.83 (1.30–2.35) 2.42 (1.94–2.90)
8 0.12 (0.05–0.44)
19
0.30 (0.16–0.43)
25
0.39 (0.2–0.54)
34
0.53 (0.35–0.71)
0.73 (0.39–1.07) 0.93 (0.63–1.23) 18 37
Prevalence of RLS
45 96
2 0.08 (0.03–0.19) 6 0.15 (0.03–0.27)
6 13
0.24 (0.05–0.44) 0.33 (0.15–0.51)
8 17
0.32 (0.10–0.55) 0.43 (0.23–0.63)
11 23
0.45 (0.18–0.71) 0.58 (0.34–0.82)
Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n n Prevalence, % (95 % CI) n
Prevalence, % (95 % CI)
Results
Respondents with definite RLS were asked to complete a second questionnaire in which they identified RLS symptoms as well as the potential correlates that they thought were related to their leg discomfort. As seen in Table 3, items 1–5 and 6–10 were used to describe RLS symptoms and perceived consequences, respectively. In response to a question about which symptoms were most troublesome,
Survey participants
Total definite RLS
The Statistical Package for the Social Sciences software (SPSS) 10.0 was used for all statistical analyses. When appropriate, differences between groups were tested by using the v2 test statistic, Student’s t statistic, and confidence intervals.
RLS symptoms and perceived consequences
Age, year
Table 1 Prevalence of definite RLS
\1 time per month
1–3 times per month
1–2 times per week
3–6 times per week
C1 time per day
Statistical analysis
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Neurol Sci Table 2 Gender analysis of definite RLS
Age, year
Definite RLS, n/N Male
P
RLS at least three times per week, n/N
Female
Male
P
Female
8–11
17/1371
28/1094
0.015
17/1371
12/1094
0.743
12–17
44/2126
52/1846
0.126
37/2126
23/1846
0.203
Total
61/3497
80/2940
0.008
54/3497
35/2940
0.226
2
Indicated P values are based on the v test
sleep disturbance, including difficulty falling asleep/interrupted sleep/poor quality of sleep, and insufficient hours of sleep were reported to be the most bothersome to participants in both groups. For children and adolescents with an RLS frequency of at least three times per week, all symptom rates were higher than those in patients experiencing a lower number of RLS episodes per week. With the exception of pain, there were no significant differences between age groups in any of the symptoms identified by respondents with definite RLS. In terms of RLS consequences, children and adolescents with definite RLS most commonly reported that they dreaded the arrival of evening/night, and this was followed by the description that leg discomfort had a negative impact on mood. In addition, an inability to concentrate in class and poor academic performance were significantly different between the two age groups. Finally, for participants that experienced an RLS frequency of at least three times per week, all of the reported consequences were more prevalent. Moreover, in this group, the most commonly reported effects of RLS included the dread of evening/night, negative impact on mood, and poor academic performance.
Discussion To our knowledge, this is the first population-based study to investigate the prevalence and impact of RLS in Chinese children and adolescents according to the criteria proposed by the IRLSSG in 2003 [1]. We found that the prevalence of definite RLS in our total population was 2.2 % (1.8 % of children 8–11 years old and 2.4 % of adolescents 12–17 years old). In contrast to the limited data of RLS in the Chinese pediatric population, the prevalence of definite RLS in children and adolescents in the US, Western Europe, and Turkey has been reported. For example, Picchietti et al. [19], who conducted the first epidemiological study on RLS, reported a prevalence of 1.9 % in children aged 8–11 years and 2.0 % in adolescents aged 12–17 years. Moreover, Turkdogan et al. [20] reported that the prevalence of RLS in Turkish children aged 10–12 years and adolescents aged 13–19 years was 2.08 and 3.21 %, respectively. Another study on Turkish adolescents aged 15–18 years reported a prevalence of 3.6 % [21]. The above results show that, unlike adolescents, the prevalence of definite RLS in children across studies is similar. In our report, we found that the prevalence of RLS tended to
Table 3 Symptoms and consequences reported by children and adolescents Symptoms and consequences
Difficulty falling asleep/interrupted sleep/poor quality of sleep Daytime sleepiness
Definite RLS
P
RLS at least three times per week
Age 8–11 years
Age 12–17 years
Age 8–11 years
Age 12–17 years
n
%
n
%
n
%
n
%
26
57.8
52
54.2
27
93.1
50
83.3
0.688
P
0.379
8
17.8
26
27.1
0.229
10
34.5
25
41.7
0.625
Insufficient hours of sleep
19
42.2
45
46.9
0.605
16
55.2
39
65.0
0.565
Exhaustion/fatigue Pain
14 22
31.1 48.9
35 22
36.5 22.9
0.534 0.002
12 17
41.4 58.6
28 17
46.7 28.3
0.759 0.009
9
20.0
36
37.5
0.038
12
41.4
29
48.3
0.666
Inability to concentrate in class Poor academic performance (compared with no RLS time)
10
22.2
44
45.8
0.007
16
55.2
36
60.0
0.823
Negative impact on mood
26
57.8
45
46.9
0.227
20
69.0
34
56.7
0.304
Irritability
13
28.9
22
22.9
0.444
10
34.5
19
31.7
0.739
Dreading the arrival of evening/night
26
57.8
52
54.2
0.688
22
75.9
41
68.3
0.491
4
8.9
7
7.3
0.742
1
3.4
7
11.7
0.225
Other effect not listed Indicated P values are based on the v2 test
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Neurol Sci
increase with age, indicating that the age range used in different studies may determine the prevalence of RLS. In addition, the limited number of population-based surveys makes it difficult to directly compare these studies. In the current investigation, we revealed that there was no significant difference in RLS prevalence between participants aged 8–11 years and those aged 12–17 years (children vs. adolescents). Similar results appeared in the study conducted by Picchietti et al. [19]. However, the study conducted by Turkdogan et al. [20] revealed a statistically significant relationship between RLS and age. It should be noted that the prevalence of RLS reported by Picchietti et al. was on participants who experienced RLS symptoms at least once a month, and that the prevalence of RLS in children and adolescents was very close (1.9 vs. 2.0 %). On the other hand, our study as well as the study that was conducted by Turkdogan et al. did not limit participants to those experiencing a certain RLS frequency. In our study, the prevalence of RLS in participants that experienced a restless legs episode less than once per month was significantly different between children and adolescents (0.08 vs. 0.15 %, P \ 0.01), which may contribute to the increasing trend of RLS prevalence with age. Our study demonstrated that the prevalence of RLS in females was significantly higher than in males (1.7 vs. 2.7 %, P \ 0.01), which replicates a well-known finding in adults that RLS prevalence is influenced by gender. However, the relationship between the prevalence of RLS and gender in children and adolescents is controversial [19–21]. Although parity is considered as a major factor in explaining the sex difference in adults [16], it is obvious that it does not apply to this study. Turkdogan et al. found that the gender effect occurred after 15 years of age in their; however, our results revealed that the gender difference occurred in children aged 8–11 years old. Thus, more studies regarding RLS prevalence in children and adolescents are needed to clarify this point. A wide range of RLS symptoms and perceived consequences were reported in our study. Some symptoms caused by unpleasant leg sensations, such as the ‘‘urge or need to move’’ or ‘‘inability to get comfortable’’, have been frequently reported; therefore, we did not investigate them in this study. Our results showed that sleep disturbance was common in children and adolescents meeting criteria for definite RLS, and that about one-third of the participants reported exhaustion/fatigue. We speculate that the disturbance of sleep led to exhaustion and fatigue. Besides, given the emerging literature on the effect of sleep disturbance on cognitive and affective function in children and adolescents, these aspects are of notable concern [22–28]. In participants who were diagnosed with definite RLS, pain was found to be significantly different between children
and adolescents. This finding suggests that the levels of tolerable pain caused by RLS may increase with age. Alternatively, this finding may be due to the fact that parents cannot correctly convey the meaning of pain to children. Interestingly, perceived consequences of RLS were also common, with the dread of the arrival of evening/night, poor academic performance, inability to concentrate in class, and negative impact on mood frequently reported in both definite RLS groups. This finding was even more pronounced in groups with an RLS frequency of at least three times per week. These results indicate that RLS may greatly impact the schoolwork of children and adolescents; thus, timely treatment of RLS is crucial. Some limitations of this study should be discussed. First, our entire study data was collected from questionnaires and no clinical or laboratory testing was applied. This situation may have led to instances of RLS misdiagnosis. Second, typical RLS symptoms might not manifest at very young ages. Alternatively, it could be that children are limited in their recognition and expression of symptoms. These two points may also contribute to the misdiagnosis of RLS. Third, we did not analyze whether treatment of the disease led to a bias in the reported prevalence of RLS.
Conclusion In this population-based study, we found that RLS in Chinese children and adolescents was common, and that adverse effects of RLS affected both sleep and daytime function. Our findings should draw attention for the need of timely RLS diagnoses and treatment in children and adolescents. Acknowledgments We thank all the participants and staff who took part in the questionnaire survey. This investigation received financial support from the Natural Science Foundation of China (U1304804) and The Youth Innovation Fund of the First Affiliated Hospital of Zhengzhou University. Conflict of interest
The authors report no conflict of interest.
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17. Tan EK, Seah A, See SJ, Lim E, Wong MC, Koh KK (2001) Restless leg syndrome in an Asian population: a study in Singapore. Mov Disord 16:577–579 18. Nomura T, Inoue Y, Kusumi M, Uemura Y, Nakashima K (2008) Prevalence of restless leg syndrome in a rural community in Japan. Mov Disord 23:2363–2369 19. Picchietti D, Allen RP, Walters AS, Davidson JE, Myers A, Ferini-Strambi L (2007) Restless legs syndrome: prevalence and impact in children and adolescents—the Peds REST study. Pediatrics 120:253–266 20. Turkdogan D, Bekiroglu N, Zaimoglu S (2011) A prevalence study of restless legs syndrome in Turkish children and adolescents. Sleep Med 12:315–321 21. Yilmaz K, Kilincaslan A, Aydin N, Kor D (2011) Prevalence and correlates of restless legs syndrome in adolescents. Dev Med Child Neurol 53:40–47 22. Dahl RE (1996) The impact of inadequate sleep on children’s daytime cognitive function. Semin Pediatr Neurol 3:44–50 23. Randazzo AC, Muehlbach MJ, Schweitzer PK, Walsh JK (1998) Cognitive function following acute sleep restriction in children ages 10-14. Sleep 21:861–868 24. Roberts RE, Roberts CR, Chen IG (2002) Impact of insomnia on future functioning of adolescents. J Psychosom Res 53:561–569 25. Durmer JS, Dinges DF (2005) Neurocognitive consequences of sleep deprivation. Semin Neurol 25:117–129 26. Fallone G, Acebo C, Seifer R, Carskadon MA (2005) Experimental restriction of sleep opportunity in children: effects on teacher ratings. Sleep 28:1561–1567 27. Dahl RE (2005) Sleep, learning, and the developing brain: earlytobed as a healthy and wise choice for school aged children. Sleep 28:1498–1499 28. Beebe DW (2006) Neurobehavioral morbidity associated with disordered breathing during sleep in children: a comprehensive review. Sleep 29:1115–1134
ORIGINAL ARTICLE
An epidemiologic study of restless legs syndrome among Chinese children and adolescents Rui Xue1 • Gangqiong Liu2 • Shengli Ma3 • Jing Yang4 • Ling Li2
Received: 4 February 2015 / Accepted: 1 April 2015 Ó Springer-Verlag Italia 2015
Abstract To determine the prevalence of restless legs syndrome (RLS) in Chinese children and adolescents as well as the impact of the disorder on 8–11 and 12–17 years old. This population-based study was conducted in five primary schools and seven high schools, which were randomly selected in Henan province, China. A total of 6792 students aged 8–17 years old were given a questionnaire that included the adult diagnostic criteria of RLS proposed by the International Restless Legs Study Group. Subjects who answered ‘‘yes’’ to all four questions were selected for a face-to-face interview to confirm RLS diagnosis. Individuals with definite RLS were then administered another questionnaire to survey RLS symptoms and perceived consequences. The prevalence of definite RLS in Chinese children and adolescents was 2.2 % (141/6437), with a prevalence of 1.8 % in the 8–11 years old age group and 2.4 % in the 12–17 years old age group. RLS was found to be more prevalent in females (2.7 %) than in males (1.7 %) (P = 0.008), and the prevalence of RLS was determined to & Rui Xue [email protected] 1
Department of Urology, Institute of Clinic Medicine, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
2
Department of Cardiology, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
3
Department of Emergency, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
4
Department of Neurology, The First Affiliated Hospital of Zhengzhou University, No.1 Jian She Dong Avenue, Zhengzhou 450002, People’s Republic of China
increase with age. Sleep disturbance was the most common symptom of RLS in children and adolescents. Various consequences were attributed to RLS, with participants reporting that they dreaded the arrival of evening/night most frequently, followed by the description that RLS had a negative impact on mood. These data suggest that RLS is prevalent in Chinese children and adolescents, and that those affected by this disorder suffer from disruptions to sleep and daytime function. Keywords Restless legs syndrome Children Adolescents Prevalence Chinese
Introduction Restless legs syndrome (RLS) is a common sensorimotor disorder, which is characterized by an irresistible urge to move the legs that is typically accompanied by uncomfortable and unpleasant sensations. The diagnostic criteria of RLS, which were revised by the International Restless Legs Syndrome Study Group (IRLSSG) in 2003 [1] have been adopted extensively throughout the world. According to these criteria, adults and adolescents aged 12 or older must display four essential characteristics for a definite diagnosis of RLS. On the other hand, a diagnosis of possible or probable RLS can be given to individuals who do not exhibit all four characteristics [1]. The pediatric criteria for RLS diagnosis in children and individuals with cognitive impairment have evolved out of the adult RLS criteria, with some supportive criteria proposed. Thus, under the pediatric RLS criteria, it is more difficult to diagnose a child with a definitive RLS diagnosis. It has been reported that RLS can have adverse effects on an individual’s sleep [2], mood [3], cognitive function
123
Neurol Sci
[4], and quality life [5, 6]. While the pathophysiology of RLS is still unknown, some potential factors may affect the occurrence of the disorder. For example, certain conditions or diseases, such as pregnancy, anemia, and uremia, have been found to be related to RLS in adults. In children and adolescents, RLS more frequently occurs in individuals with attention-deficit hyperactivity disorder [7], periodic legs movements in sleep (PLMS) [8, 9], migraine [10], kidney disease [11], and/or growing pains [12]. Over the last 20 years, the occurrence of RLS in adults has been increasingly recognized. For example, several epidemiological surveys have found that 5.5–11 % of adults in Western countries [13–16] have RLS, while the rates in Asian countries are lower [17, 18]. However, only a few studies on the prevalence of RLS in adolescents and children have been conducted. A Peds REST study, which was conducted in the United States (US) and the United Kingdom, revealed the prevalence of definite RLS in children aged 8–11 and 12–17 was 1.9 and 2.0 %, respectively [19]. Another study conducted in Turkey, reported the prevalence of definite RLS to be 1.7 % in children aged 10–12 and 3.2 % in those aged 13–19 [20]. These studies indicate that, although the prevalence of RLS in children is relatively lower than that in adults, RLS is not a rare condition in childhood. Taken together, we feel that epidemiological studies on RLS in the pediatric population are still very limited. Thus, to contribute to the pediatric perspective of RLS, the aims of the current study were to determine the prevalence of definite RLS in Chinese children and adolescents as well as to investigate conditions that correlate with RLS in this population.
to give students a questionnaire that was designed to investigate the essential diagnostic criteria of RLS for children and adolescents, which were proposed by the IRLSSG in 2003 [1]. Participants were stratified by age into two groups: 8–11 and 12–17 years old. Adult RLS criteria were used in questionnaires administered to adolescents aged 12 or older, while pediatric criteria were used for participants aged 11 years or younger (Table 1). After questionnaires were distributed, the aim and procedure of the study were clearly explained, and students were asked to complete their surveys at home. For participants in the younger age group, parents were asked to complete the questionnaire with the child present for the section that contained questions about leg feelings. All questionnaires were collected 3 days after they were sent out. No matter what age group the students belonged to, participants that answered ‘‘yes’’ to questions 1, 2, 3, and 4 were interviewed by a senior child neurologist (J. Y.) to determine whether they were really suffering from RLS or whether their questionnaire results were just a false positive. Subjects who were diagnosed as having definite RLS were required to fill out an additional questionnaire aimed to survey the following items: frequency of RLS (\1 time per month; 1–3 times per month; 1–2 times per week; 3–6 times per week; C1 time per day), impact of symptoms on sleep (difficulty falling asleep, interrupted sleep, poor sleep quality, excessive daytime sleep, insufficient hours of sleep), impact of symptoms on daytime function (inability to concentrate in class), health status (exhaustion, fatigue), study (poor academic performance), mood (irritability, dreading the arrival of evening/night), and other aspects affected by RLS (displayed in Table 2 as ‘‘other effect not listed’’).
Materials and methods Definition of RLS Population From September 2014 to January 2015, a cross-sectional epidemiological survey of RLS among Chinese children and adolescents was carried out in Henan Province, which is located in the central-east part of China. The study took place in five primary schools and seven high schools. All study participants were randomly selected, and a total of 6437 students ranging in age from 8 to 17 years were included in this study. All participants and their parents were informed about the nature of the research and provided us with written consent that was approved by the local ethics committee (No. CHN287/14). Procedures After obtaining permission from the authorities of each school, a trained researcher visited participating classrooms
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In this study, children aged 11 and younger were diagnosed as having definite RLS based on criteria set forth by the IRLSSG for pediatric RLS. Criteria for pediatric RLS proposes the following items in addition to the four essential adult RLS criteria: a consistent description of leg discomfort in a child’s own words with the presence of unpleasant sensations, or an answer of ‘‘yes’’ to both ‘‘Did you experience sleep disturbance’’ and ‘‘Do you have a biological parent or sibling with definite RLS’’. According to the IRLSSG diagnostic criteria, a third supportive criterion (a PLMS index of C5/h on polysomnography) should also be used as an item for diagnosis of RLS. However, this criterion was disregarded in our study because its use is inconvenient in an epidemiological survey, and it is more commonly used in clinical studies. For adolescents aged 12 or over, adult diagnostic criteria were used.
Neurol Sci
0.85 (0.63–1.08) 55
Of the 6792 questionnaires distributed, 6437 (94.8 %) were returned with valid answers that were entered into the final analysis. A total of 152 children and adolescents met all four essential RLS criteria in our questionnaire. Our interview confirmed the diagnosis of definite RLS in 2.2 % of these students (141) (Table 1). The prevalence rate across different age groups was 1.8 % for ages 8–11 years and 2.4 % for ages 12–17 years; however, there was no significant difference between the two groups (P = 0.115). Of these, 4.4 % (2/45) of participants in the younger age group and 5.2 % (5/96) in the older age group reported that the frequency of RLS was \1 time per month, corresponding with prevalence estimates of 0.08 and 0.13 %, respectively. On the other hand, 40 % (18/45) of children in the younger age group and 38.5 % (37/96) of adolescents reported an RLS frequency of C1 times per day, corresponding with prevalence estimates of 0.73 and 0.93 %, respectively. An increasing trend of prevalence from mild RLS to moderate or severe RLS was found from these data (Table 1). In the total sample, the prevalence of definite RLS was 1.7 % (61/3497) in males and 2.7 % (80/2940) in females, and this difference was statistically significant (P = 0.008). The distribution of the male:female ratio by age group demonstrated a prominent gender difference in the 8–1 years old group. However, for participants that reported an RLS frequency of at least three times per week, no significant gender differences were found in either age group. See Table 2 for a detailed analysis of gender data for the definite RLS groups.
2.19 (1.83–2.55) 141 6437
2465 3972 8–11 12–17
Total
CI confidence interval
1.83 (1.30–2.35) 2.42 (1.94–2.90)
8 0.12 (0.05–0.44)
19
0.30 (0.16–0.43)
25
0.39 (0.2–0.54)
34
0.53 (0.35–0.71)
0.73 (0.39–1.07) 0.93 (0.63–1.23) 18 37
Prevalence of RLS
45 96
2 0.08 (0.03–0.19) 6 0.15 (0.03–0.27)
6 13
0.24 (0.05–0.44) 0.33 (0.15–0.51)
8 17
0.32 (0.10–0.55) 0.43 (0.23–0.63)
11 23
0.45 (0.18–0.71) 0.58 (0.34–0.82)
Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n Prevalence, % (95 % CI) n n Prevalence, % (95 % CI) n
Prevalence, % (95 % CI)
Results
Respondents with definite RLS were asked to complete a second questionnaire in which they identified RLS symptoms as well as the potential correlates that they thought were related to their leg discomfort. As seen in Table 3, items 1–5 and 6–10 were used to describe RLS symptoms and perceived consequences, respectively. In response to a question about which symptoms were most troublesome,
Survey participants
Total definite RLS
The Statistical Package for the Social Sciences software (SPSS) 10.0 was used for all statistical analyses. When appropriate, differences between groups were tested by using the v2 test statistic, Student’s t statistic, and confidence intervals.
RLS symptoms and perceived consequences
Age, year
Table 1 Prevalence of definite RLS
\1 time per month
1–3 times per month
1–2 times per week
3–6 times per week
C1 time per day
Statistical analysis
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Neurol Sci Table 2 Gender analysis of definite RLS
Age, year
Definite RLS, n/N Male
P
RLS at least three times per week, n/N
Female
Male
P
Female
8–11
17/1371
28/1094
0.015
17/1371
12/1094
0.743
12–17
44/2126
52/1846
0.126
37/2126
23/1846
0.203
Total
61/3497
80/2940
0.008
54/3497
35/2940
0.226
2
Indicated P values are based on the v test
sleep disturbance, including difficulty falling asleep/interrupted sleep/poor quality of sleep, and insufficient hours of sleep were reported to be the most bothersome to participants in both groups. For children and adolescents with an RLS frequency of at least three times per week, all symptom rates were higher than those in patients experiencing a lower number of RLS episodes per week. With the exception of pain, there were no significant differences between age groups in any of the symptoms identified by respondents with definite RLS. In terms of RLS consequences, children and adolescents with definite RLS most commonly reported that they dreaded the arrival of evening/night, and this was followed by the description that leg discomfort had a negative impact on mood. In addition, an inability to concentrate in class and poor academic performance were significantly different between the two age groups. Finally, for participants that experienced an RLS frequency of at least three times per week, all of the reported consequences were more prevalent. Moreover, in this group, the most commonly reported effects of RLS included the dread of evening/night, negative impact on mood, and poor academic performance.
Discussion To our knowledge, this is the first population-based study to investigate the prevalence and impact of RLS in Chinese children and adolescents according to the criteria proposed by the IRLSSG in 2003 [1]. We found that the prevalence of definite RLS in our total population was 2.2 % (1.8 % of children 8–11 years old and 2.4 % of adolescents 12–17 years old). In contrast to the limited data of RLS in the Chinese pediatric population, the prevalence of definite RLS in children and adolescents in the US, Western Europe, and Turkey has been reported. For example, Picchietti et al. [19], who conducted the first epidemiological study on RLS, reported a prevalence of 1.9 % in children aged 8–11 years and 2.0 % in adolescents aged 12–17 years. Moreover, Turkdogan et al. [20] reported that the prevalence of RLS in Turkish children aged 10–12 years and adolescents aged 13–19 years was 2.08 and 3.21 %, respectively. Another study on Turkish adolescents aged 15–18 years reported a prevalence of 3.6 % [21]. The above results show that, unlike adolescents, the prevalence of definite RLS in children across studies is similar. In our report, we found that the prevalence of RLS tended to
Table 3 Symptoms and consequences reported by children and adolescents Symptoms and consequences
Difficulty falling asleep/interrupted sleep/poor quality of sleep Daytime sleepiness
Definite RLS
P
RLS at least three times per week
Age 8–11 years
Age 12–17 years
Age 8–11 years
Age 12–17 years
n
%
n
%
n
%
n
%
26
57.8
52
54.2
27
93.1
50
83.3
0.688
P
0.379
8
17.8
26
27.1
0.229
10
34.5
25
41.7
0.625
Insufficient hours of sleep
19
42.2
45
46.9
0.605
16
55.2
39
65.0
0.565
Exhaustion/fatigue Pain
14 22
31.1 48.9
35 22
36.5 22.9
0.534 0.002
12 17
41.4 58.6
28 17
46.7 28.3
0.759 0.009
9
20.0
36
37.5
0.038
12
41.4
29
48.3
0.666
Inability to concentrate in class Poor academic performance (compared with no RLS time)
10
22.2
44
45.8
0.007
16
55.2
36
60.0
0.823
Negative impact on mood
26
57.8
45
46.9
0.227
20
69.0
34
56.7
0.304
Irritability
13
28.9
22
22.9
0.444
10
34.5
19
31.7
0.739
Dreading the arrival of evening/night
26
57.8
52
54.2
0.688
22
75.9
41
68.3
0.491
4
8.9
7
7.3
0.742
1
3.4
7
11.7
0.225
Other effect not listed Indicated P values are based on the v2 test
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increase with age, indicating that the age range used in different studies may determine the prevalence of RLS. In addition, the limited number of population-based surveys makes it difficult to directly compare these studies. In the current investigation, we revealed that there was no significant difference in RLS prevalence between participants aged 8–11 years and those aged 12–17 years (children vs. adolescents). Similar results appeared in the study conducted by Picchietti et al. [19]. However, the study conducted by Turkdogan et al. [20] revealed a statistically significant relationship between RLS and age. It should be noted that the prevalence of RLS reported by Picchietti et al. was on participants who experienced RLS symptoms at least once a month, and that the prevalence of RLS in children and adolescents was very close (1.9 vs. 2.0 %). On the other hand, our study as well as the study that was conducted by Turkdogan et al. did not limit participants to those experiencing a certain RLS frequency. In our study, the prevalence of RLS in participants that experienced a restless legs episode less than once per month was significantly different between children and adolescents (0.08 vs. 0.15 %, P \ 0.01), which may contribute to the increasing trend of RLS prevalence with age. Our study demonstrated that the prevalence of RLS in females was significantly higher than in males (1.7 vs. 2.7 %, P \ 0.01), which replicates a well-known finding in adults that RLS prevalence is influenced by gender. However, the relationship between the prevalence of RLS and gender in children and adolescents is controversial [19–21]. Although parity is considered as a major factor in explaining the sex difference in adults [16], it is obvious that it does not apply to this study. Turkdogan et al. found that the gender effect occurred after 15 years of age in their; however, our results revealed that the gender difference occurred in children aged 8–11 years old. Thus, more studies regarding RLS prevalence in children and adolescents are needed to clarify this point. A wide range of RLS symptoms and perceived consequences were reported in our study. Some symptoms caused by unpleasant leg sensations, such as the ‘‘urge or need to move’’ or ‘‘inability to get comfortable’’, have been frequently reported; therefore, we did not investigate them in this study. Our results showed that sleep disturbance was common in children and adolescents meeting criteria for definite RLS, and that about one-third of the participants reported exhaustion/fatigue. We speculate that the disturbance of sleep led to exhaustion and fatigue. Besides, given the emerging literature on the effect of sleep disturbance on cognitive and affective function in children and adolescents, these aspects are of notable concern [22–28]. In participants who were diagnosed with definite RLS, pain was found to be significantly different between children
and adolescents. This finding suggests that the levels of tolerable pain caused by RLS may increase with age. Alternatively, this finding may be due to the fact that parents cannot correctly convey the meaning of pain to children. Interestingly, perceived consequences of RLS were also common, with the dread of the arrival of evening/night, poor academic performance, inability to concentrate in class, and negative impact on mood frequently reported in both definite RLS groups. This finding was even more pronounced in groups with an RLS frequency of at least three times per week. These results indicate that RLS may greatly impact the schoolwork of children and adolescents; thus, timely treatment of RLS is crucial. Some limitations of this study should be discussed. First, our entire study data was collected from questionnaires and no clinical or laboratory testing was applied. This situation may have led to instances of RLS misdiagnosis. Second, typical RLS symptoms might not manifest at very young ages. Alternatively, it could be that children are limited in their recognition and expression of symptoms. These two points may also contribute to the misdiagnosis of RLS. Third, we did not analyze whether treatment of the disease led to a bias in the reported prevalence of RLS.
Conclusion In this population-based study, we found that RLS in Chinese children and adolescents was common, and that adverse effects of RLS affected both sleep and daytime function. Our findings should draw attention for the need of timely RLS diagnoses and treatment in children and adolescents. Acknowledgments We thank all the participants and staff who took part in the questionnaire survey. This investigation received financial support from the Natural Science Foundation of China (U1304804) and The Youth Innovation Fund of the First Affiliated Hospital of Zhengzhou University. Conflict of interest
The authors report no conflict of interest.
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