Periodic limb movements in sleep--endophenotype for restless legs syndrome?

Peripheral Iron Metabolism is Associated with Leg Movements on Polysomnography but Not with the Severity of Restless Legs Syndrome or Its Impact on Patients

Purpose

This study investigated the associations of peripheral iron status with different manifestations of restless legs syndrome (RLS), including leg movements (LMs) on polysomnography (PSG), disease severity, and impact on patients.

Patients and Methods

In this cross-sectional study, 108 patients with RLS were enrolled at Sir Run Run Shaw Hospital's Center for Sleep Medicine. Demographic information, disease characteristics, RLS severity, and impact on patients were assessed through a semi-structured questionnaire. Peripheral iron indicators [serum ferritin, iron, and transferrin concentrations; unsaturated iron-binding capacity (UIBC) and total iron-binding capacity (TIBC); transferrin saturation (TSAT)] were measured following PSG to assess sleep stages, respiratory events, microarousals and LM parameters. Data from patients with and without ferritin concentration < 50 µg/L were compared in crude analyses, and Spearman correlations of other iron indicators with RLS data were examined. An ordinal logistic regression model was used to adjust for age, sex, body mass index, years of education, age at the time of RLS onset, prior treatment (yes/no), C-reactive protein (CRP)/hemoglobin level, total sleep time and apnea-hypopnea index.

Results

Multivariate analysis showed that periodic LMs during sleep (PLMS) and other LM parameters were significantly associated with a ferritin concentration < 50 µg/L, UIBC, TIBC, and serum transferrin concentration, but not serum iron or TSAT. By contrast, the severity and impact of RLS were not associated with a ferritin concentration < 50 µg/L or other peripheral iron indicators in the multivariate model.

Conclusion

In this study, peripheral iron status was associated mainly with motor components (LMs on PSG) rather than sensory components (severity and impact of RLS) after adequately controlling for potential confounders, such as CRP and hemoglobin levels. Commonly used peripheral iron metabolism indicators may therefore not be ideal biomarkers of RLS severity or impact on patients.

Usefulness of Restless Legs Symptoms to Predict Adverse Cardiovascular Outcomes in Men With Coronary Artery Disease

The relationship between restless legs syndrome (RLS) and cardiovascular disease remains enigmatic in the general population, and its prognostic value in patients with coronary artery disease (CAD) is unknown. In this study, the frequency of RLS-like symptoms was assessed using a validated instrument in 3,266 patients undergoing cardiac catheterization (mean age 64 years, 62% male, 23% Black, and 74% with obstructive CAD). Patients were followed for primary end points of cardiovascular death or incident myocardial infarction. Fine and Gray hazard models explored the association between RLS and incident events after adjustment for demographic and clinical risk factors. In the total cohort, 29% of patients reported mild (rare or sometimes) symptoms, and 15% of patients had moderate/severe (often to almost always) symptoms of RLS. Female sex (odds ratio [OR] 2.11, 95% confidence interval (CI), 1.68 to 2.57), body mass index (OR 1.12 per 5 kg/m², 95% CI, 1.04 to 1.22), diabetes (OR 1.43, 95%,1.15 to 1.79), and β-blocker use (OR 1.35, 95% CI, 1.07 to 1.72) were independently associated with moderate/severe symptoms of RLS compared with no symptoms. Over a 5-year follow-up period, 991 patients suffered an adverse event. Compared with those with no symptoms, patients with moderate/severe RLS had significantly higher risk of the primary end point (hazard ratio [HR] = 1.33, 95%),CI 1.01 to 1.76) after adjustment for demographic and clinical risk factors. The association was more significant in men than women, HR 1.98, 95% CI, 1.41 to 2.78 versus HR 0.99 (,95% CI, 0.64 to 1.52, p interaction= 0.013. In conclusion, among men with CAD, moderate-to-severe symptoms of RLS are associated with significantly higher risk of adverse cardiovascular outcomes, independent of traditional risk factors.

Restless legs syndrome and periodic limb movements during sleep in the Multi-Ethnic Study of Atherosclerosis

Study Objectives

To investigate the prevalence of concurrent periodic limb movements during sleep (PLMS) and restless leg syndrome (RLS), as well as the prevalence of PLMS and RLS separately. Additionally, we document these prevalences by age, race/ethnicity, sex, and obesity status.

Methods

Cross-sectional data from 2041 Multi-Ethnic Study of Atherosclerosis (MESA) Sleep ancillary study participants were used. PLMS (>15 periodic limb movements per hour of sleep) was measured by polysomnography. RLS symptoms were assessed using the 2009 International Restless Legs Syndrome Study Group clinical criteria.

Results

The prevalence of RLS with PLMS was 6.7%, RLS alone 16.1%, and PLMS alone 21.2%. RLS with PLMS was prevalent in 7.0% of whites, 4.9% of blacks, 10.1% of Hispanics, and 3.3% of Chinese-Americans. In adjusted models, odds of RLS with PLMS was higher for those older than 67 years versus those younger (odds ratio [OR] [95% confidence interval [CI]] = 1.62 [1.09-2.40]). Relative to white participants, the prevalence of RLS with PLMS tended to be lower among blacks (0.56 [0.32-0.96]). The prevalence of concurrent RLS and PLMS did not statistically differ by sex or obesity status. RLS alone was more common in women.

Conclusions

Approximately 7% of our sample had RLS with PLMS ("electro-clinical RLS"). This condition was more common among older individuals, did not vary by sex, and was less common among blacks. The findings provide some of the first information about the prevalence of concurrent RLS and PLMS in a community-based sample and show distinct sex and race associations for RLS versus electro-clinical RLS.

Sleep-Wake Disorders of Childhood

PURPOSE OF REVIEW

Sleep-wake disorders occur in 10% to 28% of children and differ somewhat in pathophysiology and management from sleep-wake disorders in adults. This article discusses the diagnosis and management of key childhood sleep disorders.

RECENT FINDINGS

The role of sleep in memory consolidation and in the facilitation of learning has been increasingly recognized, even at the toddler stage. Cataplexy, a key feature of narcolepsy type 1, may be subtle in childhood and characterized by transient muscle weakness isolated to the face. Children with obstructive sleep apnea and restless legs syndrome display prominent neurobehavioral symptoms such as daytime inattentiveness and hyperactivity, so it is important to elicit a sleep history when these symptoms are encountered. Systemic iron deficiency occurs in about two-thirds of children with restless legs syndrome and is easily treatable. Parasomnias arising out of non-rapid eye movement (REM) sleep, such as confusional arousals and sleepwalking, may be difficult to distinguish from nocturnal seizures, and, in many cases, video-EEG polysomnography is required to differentiate between causes.

SUMMARY

Clinicians should routinely integrate the assessment of sleep-wake function into their practices of neurology and child neurology because of the opportunity to improve the quality of life of their patients.

Restless leg syndrome in chronic hemodialysis patients in Mashhad hemodialysis centers

Introduction: Restless leg syndrome (RLS) is a sensory motor disorder. Patients with this syndrome have serious and uncontrollable desire to move their legs, which is mostly due to an uncomfortable feeling intensified when they are motionless. It may be a genetic disorder or secondary to iron deficiency, neurodegenerations, pregnancy, some drugs and severe kidney diseases.

Objectives: This study was designed to find out the prevalence and its risk factors of RLS in hemodialysis patients.

Patients and Methods: This multicenter cross-sectional study was done on 260 hemodialysis patients. The prevalence of RLS was measured using International Restless Legs Syndrome Study Group (IRLSSG)’s RLS Questionnaire (RLSQ). Potential risk factors for RLS including underlying cause of chronic renal failure, duration on dialysis, biochemical tests, dialysis adequacy, and erythropoietin and also venofer dosage in recent month and demographic data were also evaluated.

Results: The prevalence of RLS was 55% including 59.4% males and 40.6% females. Their mean age of RLS patients and their dialysis duration were significantly higher than other group (P<0.05). Their body mass index (BMI) and serum calcium were significantly higher (P<0.05). However erythropoietin dosage and serum hemoglobin level were lower in RLS patients (P<0.05). Significant predictors of RLS were history of diabetes mellitus (DM), hypertension (HTN), smoking (P<0.05). There was not significant relation between RLS and dialysis adequacy, serum intact parathyroid hormone (iPTH), urea, ferritin and venofer dosage (P>0.05).

Conclusion: According to the results, RLS is a common disorder in hemodialysis patients which can affect strongly on their life. So particular attention and sooner diagnosis of RLS in high risk patients for better management is necessary.

Iron, dopamine, genetics, and hormones in the pathophysiology of restless legs syndrome

Restless legs syndrome (RLS) is a common, chronic neurologic condition, which causes a persistent urge to move the legs in the evening that interferes with sleep. Human and animal studies have been used to study the pathophysiologic state of RLS and much has been learned about the iron and dopamine systems in relation to RLS. Human neuropathologic and imaging studies have consistently shown decreased iron in different brain regions including substantia nigra and thalamus. These same areas also demonstrate a state of relative dopamine excess. While it is not known how these changes in dopamine or iron produce the symptoms of RLS, genetic and hormone studies of RLS have identified other biologic systems or genes, such as the endogenous opioid and melanocortin systems and BTBD9 and MEIS1, that may explain some of the iron or dopamine changes in relation to RLS. This manuscript will review what is known about the pathophysiology of RLS, especially as it relates to changes in iron, dopamine, genetics, and hormonal systems.

Restless Legs Syndrome and Depression: Effect Mediation by Disturbed Sleep and Periodic Limb Movements

OBJECTIVE

To investigate an association between restless legs syndrome (RLS) and depression and to what extent sleep disturbance, periodic limb movements during sleep (PLMS), and antidepressant medication mediate this relationship.

METHODS

A cross-sectional analysis was conducted of the Osteoporotic Fractures in Older Men Study data in 982 men assessed for RLS (International RLS Study Group scale [IRLSS]) and depression (Geriatric Depression Scale [GDS]), who underwent actigraphy (for sleep latency/efficiency) and polysomnography (for PLMS). Men were split into three groups: no RLS (N = 815), mild RLS (IRLSS ≤ 12, N = 85), moderate-to-severe RLS (IRLSS > 12, N = 82). Depression was defined as GDS score ≥ 6. Logistic and linear regression assessed associations of RLS and depression or number depressive symptoms, respectively. Models were adjusted for age, site, race, education, body mass index, personal habits, benzodiazepine/dopaminergic medication, physical activity, cardiovascular risk factors, and apnea-hypopnea index.

RESULTS

Of 982 men, 167 (17.0%) had RLS. Depression was significantly associated with moderate-to-severe RLS after adjustment (versus no RLS: OR [95% CI] 2.85 [1.23, 6.64]). Further adjustment for potential mediators attenuated effect size modestly, most for sleep efficiency (OR: 2.85-2.55). Compared with no RLS, moderate-to-severe RLS was associated with the number of depressive symptoms after adjustment (adjusted means [95% CI]; no RLS: 1.14 [1.05, 1.24] versus IRLSS > 12: 1.69 [1.32, 2.11]). Further adjustment for potential mediators did not alter effect size. For men with PLMS index at least median, number of depressive symptoms significantly increased as RLS category became more severe.

CONCLUSION

Depression is more common as RLS severity worsens. The RLS-depression relationship is modestly explained by sleep disturbance and PLMS.

Prevalence and Characteristics of Periodic Limb Movements during Sleep in Korean Adult Patients with Restless Legs Syndrome

STUDY OBJECTIVES

The aim of this study was to investigate the prevalence and characteristics of periodic limb movements during sleep (PLMS) in Korean patients with restless legs syndrome (RLS).

METHODS

Unmedicated adult patients with idiopathic RLS (n = 354) who underwent polysomnography at three major sleep centers in tertiary hospitals were included. Characteristics of PLMS in RLS were analyzed using the time structure of polysomnographically recorded leg movements and periodicity indices (PIs). RLS severity and subjective sleep quality were assessed.

RESULTS

Out of 354 patients with idiopathic RLS (mean age: 52.9 ± 12.0 years), 150 patients (42.3%) had RLS with a PLMS index greater than 15 events/h, and 204 (57.9%) had a PLMS index greater than 5 events/h. The distribution of inter-LM intervals was bimodal, and high PIs (0.86 ± 0.10) were observed in patients with RLS and PLMS (PLMS index > 15 events/h). The PLMS index was positively correlated with age (r = 0.228; p < 0.001), the periodic limb movements in wakefulness index (r = 0.455, p < 0.001) and arousal index (r = 0.174, p = 0.014), but not with RLS severity and parameters of sleep quality. In multivariate analysis, age and male gender were independently associated with PLMS > 15 events/h.

CONCLUSIONS

The prevalence of PLMS in Korean patients with RLS was lower than that observed in Western countries, but the characteristics of PLMS were not different. Ethnic differences and/or different genetic backgrounds may contribute to the varying prevalence of PLMS in RLS.

Sleep Disturbances and Behavioral Disturbances in Children and Adolescents

Sleep deprivation and sleep disorders are commonly seen in children and adolescents. They are often undiagnosed and undertreated. A balance of circadian rhythm and homeostatic drive determine sleep quality, quantity, and timing, which changes across the developmental years. Environmental and lifestyle factors can affect sleep quality and quantity and lead to sleep deprivation. A comprehensive assessment of sleep disorders includes parental report, children's self-report, and school functioning. Diagnostic tools are used in diagnosing and treating sleep disorders.

Genetic associations of periodic limb movements of sleep in the elderly for the MrOS sleep study

OBJECTIVE

The objective of this study was to assess the relationship between single-nucleotide polymorphisms associated with restless legs syndrome and periodic limb movements of sleep in a population cohort of elderly individuals.

METHODS

Single-nucleotide polymorphisms previously associated with periodic limb movements of sleep or restless legs syndrome were analyzed in 2356 white male participants in the Osteoporotic Fractures in Men Sleep Study cohort. The associations between single-nucleotide polymorphisms and polysomnographically measured periodic limb movement index ≥15 were examined with logistic regression adjusted for age, ancestry markers, and periodic limb movements of sleep risk factors.

RESULTS

Of the men in this cohort, 61% had a periodic limb movement index ≥15. Significant associations were observed between a periodic limb movement index ≥15 and the number of risk alleles for the two BTBD9 single-nucleotide polymorphisms (rs9357271[T], odds ratio [OR] = 1.38, 95% confidence interval [CI] 1.20-1.58; and rs3923809[A], OR = 1.43, 95% CI 1.26-1.63), one of the MEIS1 single-nucleotide polymorphisms (rs2300478[G], OR = 1.31, 95% CI 1.14-1.51) and the mitogen-activated protein kinase kinase 5 (MAP2K5)/Ski family transcriptional corepressor 1 (SKOR1) single-nucleotide polymorphism (rs1026732[G], OR = 1.16, 95% CI 1.02-1.31). In a multivariable model controlling for each of the two MEIS1 single-nucleotide polymorphisms, the rs6710341[A] single-nucleotide polymorphism became a significant risk allele (OR = 1.59, 95% CI 1.26-2.00).

CONCLUSIONS

Our findings confirm an association between the BTBD9, MEIS1, and MAP2K5/SKOR1 single-nucleotide polymorphisms and periodic limb movements of sleep in an elderly cohort not selected for the presence of restless legs syndrome.

The Molecular Genetics of Restless Legs Syndrome

Restless legs syndrome (RLS) is a common sensorimotor trait defined by symptoms that interfere with sleep onset and maintenance in a clinically meaningful way. Nonvolitional myoclonus while awake and asleep is a sign of the disorder and an informative endophenotype. The genetic contributions to RLS/periodic leg movements are substantial, are among the most robust defined to date for a common disease, and account for much of the variance in disease expressivity. The disorder is polygenic, as revealed by recent genome-wide association studies. Experimental studies are revealing mechanistic details of how these common variants might influence RLS expressivity.

Genetic variants associated with sleep disorders

OBJECTIVE

The diagnostic boundaries of sleep disorders are under considerable debate. The main sleep disorders are partly heritable; therefore, defining heritable pathophysiologic mechanisms could delineate diagnoses and suggest treatment. We collected clinical data and DNA from consenting patients scheduled to undergo clinical polysomnograms, to expand our understanding of the polymorphisms associated with the phenotypes of particular sleep disorders.

METHODS

Patients at least 21 years of age were recruited to contribute research questionnaires, and to provide access to their medical records, saliva for deoxyribonucleic acid (DNA), and polysomnographic data. From these complex data, 38 partly overlapping phenotypes were derived indicating complaints, subjective and objective sleep timing, and polysomnographic disturbances. A custom chip was used to genotype 768 single-nucleotide polymorphisms (SNPs). Additional assays derived ancestry-informative markers (eg, 751 participants of European ancestry). Linear regressions controlling for age, gender, and ancestry were used to assess the associations of each phenotype with each of the SNPs, highlighting those with Bonferroni-corrected significance.

RESULTS

In peroxisome proliferator-activated receptor gamma, coactivator 1 beta (PPARGC1B), rs6888451 was associated with several markers of obstructive sleep apnea. In aryl hydrocarbon receptor nuclear translocator-like (ARNTL), rs10766071 was associated with decreased polysomnographic sleep duration. The association of rs3923809 in BTBD9 with periodic limb movements in sleep was confirmed. SNPs in casein kinase 1 delta (CSNK1D rs11552085), cryptochrome 1 (CRY1 rs4964515), and retinoic acid receptor-related orphan receptor A (RORA rs11071547) were less persuasively associated with sleep latency and time of falling asleep.

CONCLUSIONS

SNPs associated with several sleep phenotypes were suggested, but due to risks of false discovery, independent replications are needed before the importance of these associations can be assessed, followed by investigation of molecular mechanisms.

Periodic limb movements during REM sleep in multiple sclerosis: a previously undescribed entity

BACKGROUND

There are few studies describing periodic limb movement syndrome (PLMS) in rapid eye movement (REM) sleep in patients with narcolepsy, restless legs syndrome, REM sleep behavior disorder, and spinal cord injury, and to a lesser extent, in insomnia patients and healthy controls, but no published cases in multiple sclerosis (MS). The aim of this study was to investigate PLMS in REM sleep in MS and to analyze whether it is associated with age, sex, disability, and laboratory findings.

METHODS

From a study of MS patients originally published in 2011, we retrospectively analyzed periodic limb movements (PLMs) during REM sleep by classifying patients into two subgroups: PLM during REM sleep greater than or equal to ten per hour of REM sleep (n=7) vs less than ten per hour of REM sleep (n=59). A univariate analysis between PLM and disability, age, sex, laboratory findings, and polysomnographic data was performed.

RESULTS

MS patients with more than ten PLMs per hour of REM sleep showed a significantly higher disability measured by the Kurtzke expanded disability status scale (EDSS) (P=0.023). The presence of more than ten PLMs per hour of REM sleep was associated with a greater likelihood of disability (odds ratio 22.1; 95% confidence interval 3.5-139.7; P<0.0001), whereas there were no differences in laboratory and other polysomnographic findings.

CONCLUSION

PLMs during REM sleep were not described in MS earlier, and they are associated with disability measured by the EDSS.

Growing pains and periodic limb movements of sleep in children

AIM

To investigate whether there was any association between growing pains (GP) and periodic limb movements of sleep (PLMS) in children referred for polysomnography (PSG), in light of the possible shared genetic determinants between GP and restless legs syndrome.

METHODS

Records of all 903 children who underwent PSG at a paediatric hospital between January 2009 and May 2010 were retrospectively reviewed. Children aged 3-16 years, without neuromuscular or neurological/developmental disorders who were seen by a single sleep physician were included in the analysis. Data extracted included: current GP, PLMS index, mixed obstructive apnoea/hypopnoea index and patient demographics. GP was diagnosed in the pre-PSG consultation.

RESULTS

GP was recorded in 43 of the eligible 230 children referred for PSG of whom 25.6% had a PLMS index ≥ 5/h, significantly higher than in the children without GP (10.2%) (odds ratio 3.04, χ(2) = 6.0, P = 0.014). The adjusted odds ratio for the association between GP and PLMS remained significant at 2.53 (95% CI 1.1-6.1, P < 0.05). A PLMS index ≥ 5/h was recorded in 30 of the 230 participants. GP and PLMS were also significantly multivariately associated with restlessness as the indication for PSG.

CONCLUSIONS

Children with GP were three times more likely to have a PLMS index ≥ 5/h than children without GP on PSG. These results suggest that GP may be associated with PLMS, giving greater support for the hypothesis that GP might lie on the phenotypic spectrum of restless legs syndrome.

Respiratory-related leg movements and their relationship with periodic leg movements during sleep

STUDY OBJECTIVES

To describe the time structure of leg movements (LM) in obstructive sleep apnea (OSA) syndrome, in order to advance understanding of their clinical significance.

LOCATION

Sleep Research Centre, Oasi Institute (IRCCS), Troina, Italy.

SETTING

Sleep laboratory.

PATIENTS

Eighty-four patients (16 females, 68 males, mean age 55.1 y, range 29-74 y).

METHODS

Respiratory-related leg movements (RRLM) and those unrelated to respiratory events (NRLM) were examined within diagnostic polysomnograms alone and together for their distributions within the sleep period and for their periodicity.

MEASUREMENTS AND RESULTS

Patients with OSA and RRLM exhibited more periodic leg movements in sleep (PLMS), particularly in NREM sleep. A gradual decrease in number of NRLM across the sleep period was observed in patients with RRLM. This pattern was less clear for RRLM. Frequency histograms of intermovement intervals of all LMs in patients with RRLM showed a prominent first peak at 4 sec, and a second peak at approximately 24 sec coincident with that of PLMS occurring in the absence of OSA. A third peak of lowest amplitude was the broadest with a maximum at approximately 42 sec. In patients lacking RRLM, NRLM were evident with a single peak at 2-4 sec. A stepwise linear regression analysis showed that, after controlling for a diagnosis of restless legs syndrome and apnea-hypopnea index, PLMS remained significantly associated with RRLM.

CONCLUSION

The time structure of leg movements occurring in conjunction with respiratory events exhibit features of periodic leg movements in sleep occurring alone, only with a different and longer period. This brings into question the validity, both biologic and clinical, of scoring conventions with their a priori exclusion from consideration as periodic leg movements in sleep.

Frequent periodic leg movement during sleep is associated with left ventricular hypertrophy and adverse cardiovascular outcomes

BACKGROUND

Sleep disturbance caused by obstructive sleep apnea is recognized as a contributing factor to adverse cardiovascular outcomes. However, the effect of restless legs syndrome, another common cause of fragmented sleep, on cardiac structure, function, and long-term outcomes is not known. The aim of this study was to assess the effect of frequent leg movement during sleep on cardiac structure and outcomes in patients with restless legs syndrome.

METHODS

In our retrospective study, patients with restless legs syndrome referred for polysomnography were divided into those with frequent (periodic movement index > 35/hour) and infrequent (≤ 35/hour) leg movement during sleep. Long-term outcomes were determined using Kaplan-Meier and logistic regression models.

RESULTS

Of 584 patients, 47% had a periodic movement index > 35/hour. Despite similarly preserved left ventricular ejection fraction, the group with periodic movement index > 35/hour had significantly higher left ventricular mass and mass index, reflective of left ventricular hypertrophy (LVH). There were no significant baseline differences in the proportion of patients with hypertension, diabetes, hyperlipidemia, prior myocardial infarction, stroke or heart failure, or the use of antihypertensive medications between the groups. Patients with frequent periodic movement index were older, predominantly male, and had more prevalent coronary artery disease and atrial fibrillation. However, on multivariate analysis, periodic movement index > 35/hour remained the strongest predictor of LVH (odds ratio, 2.45; 95% confidence interval, 1.67-3.59; P < .001). Advanced age, female sex, and apnea-hypopnea index were other predictors of LVH. Patients with periodic movement index > 35/hour had significantly higher rates of heart failure and mortality over median 33-month follow-up.

CONCLUSIONS

Frequent periodic leg movement during sleep is an independent predictor of severe LVH and is associated with increased cardiovascular morbidity and mortality.

Spinal cord injury as a trigger to develop periodic leg movements during sleep: an evolutionary perspective

The primary trigger to periodic limb movement (PLM) during sleep is still unknown. Its association with the restless legs syndrome (RLS) is established in humans and was reported in spinal cord injury (SCI) patients classified by the American Spinal Injury Association (ASIA) as A. Its pathogenesis has not been completely unraveled, though recent advances might enhance our knowledge about those malfunctions. PLM association with central pattern generator (CPG) is one of the possible pathologic mechanisms involved. This article reviewed the advances in PLM and RLS genetics, the evolution of CPG functioning, and the neurotransmitters involved in CPG, PLM and RLS. We have proposed that SCI might be a trigger to develop PLM.

Ascertainment of iron deficiency and depletion in blood donors through screening questions for pica and restless legs syndrome

BACKGROUND

Pica and restless legs syndrome (RLS) are associated with iron depletion and deficiency. The presence of pica and RLS was prospectively assessed in blood donors.

STUDY DESIGN AND METHODS

During a 39-month period, 1236 donors deferred for fingerstick hemoglobin (Hb) level of less than 12.5 g/dL and 400 nondeferred "control" donors underwent health screening and laboratory testing (complete blood count, ferritin, iron, transferrin). Pica and RLS were assessed by direct questioning. Deferred donors and iron-deficient control donors were given 325 mg of ferrous sulfate daily for 60 days. Reassessments were performed and additional iron tablets dispensed at subsequent visits.

RESULTS

Pica was reported in 11% of donors with iron depletion or deficiency, compared with 4% of iron-replete donors (p < 0.0001). Pagophagia (ice pica) was most common and often of extraordinary intensity. Female sex, younger age, and lower mean cell volume and transferrin saturation values were strongly associated with pica. Donors with pica given iron reported a marked reduction in the desire to consume the nonnutritive substance by Days 5 to 8 of therapy, with disappearance of symptoms by Days 10 to 14. RLS was reported in 16% of subjects with iron depletion or deficiency compared with 11% of iron-replete donors (p = 0.012). Iron replacement generally resulted in improvement of RLS symptoms; however, at least 4 to 6 weeks of iron therapy was necessary.

CONCLUSION

The presence of pica is associated with a high probability of iron depletion or deficiency in blood donors; however, RLS lacks a strong correlation in this population. Screening questions for pagophagia may be useful in the ascertainment of iron deficiency in donors and may identify those who would benefit from oral iron.

Experimentally induced arousals do not elicit periodic leg motor activity during sleep in normal subjects

OBJECTIVE

To evaluate whether eliciting repetitive cortical and autonomic arousals during sleep is able to induce the occurrence of periodic leg movements during sleep (PLMS).

METHODS

Fifteen normal subjects underwent one night of uninterrupted and two sequential nights of experimental sleep fragmentation achieved by auditory and mechanical stimuli eliciting frequent EEG arousals. Sleep was polygraphically recorded and subsequently used to determine the frequency of arousals and occurrence of leg movement (LM) activity during the first (baseline) and the second fragmentation night. Also, heart rate variability parameters were obtained to assess the autonomic changes induced by the stimulation.

RESULTS

Sleep fragmentation was associated with an increase in the arousal index, percentage of sleep stage 1, and frequency of stage shifts. In addition, there was a decrease in sleep latency and in percentage of slow-wave sleep. Moreover, a significant increase in heart rate variability and especially of its sympathetic component, was also found. In contrast, parameters of the leg movement activity showed no significant change following experimental sleep fragmentation. The lack of an increase in leg movement activity was also observed in one subject who demonstrated PLMS at baseline.

CONCLUSIONS

Experimental sleep fragmentation is not associated with an increase in PLMS in normal young adults.

Non-respiratory indications for polysomnography and related procedures in children: an evidence-based review

OBJECTIVE

This evidence-based review provides a systematic and comprehensive review of the literature regarding the utility of polysomnography for the evaluation of non-respiratory sleep disorders in children including hypersomnias, parasomnias, sleep-related movement disorders, and sleep in other special populations.

METHODS

A task force of pediatric sleep medicine experts performed a systematic review of the literature regarding the use of polysomnography for non-respiratory sleep disorders in children. They identified and graded 76 papers as evidence.

RESULTS

The main results include (1) polysomnography combined with the multiple sleep latency test is useful for evaluating disorders of excessive somnolence to objectively quantify sleepiness. The results have to be interpreted with consideration of the pubertal stage and regularity of the sleep patterns of the child; (2) polysomnography is indicated in children with parasomnias or sleep related movement disorders who have a high likelihood of having obstructive sleep apnea (OSA); (3) polysomnography is not routinely indicated in children with enuresis unless there is a high likelihood of OSA; (4) polysomnography can be helpful in evaluating children with restless legs syndrome (RLS) and when periodic limb movement disorder (PLMD) is suspected.

CONCLUSIONS

These findings suggest that, in children with non-respiratory sleep disorders, polysomnography should be a part of a comprehensive sleep evaluation in selected circumstances to determine the nature of the events in more detail or when the suspicion of OSA is relatively high.

Iron deficiency anemia in infancy exerts long-term effects on the tibialis anterior motor activity during sleep in childhood

OBJECTIVES

To explore the eventual connection between iron deficiency anemia (IDA) in infancy and altered leg movements during sleep in a 10-year follow-up study in children who did or did not have IDA in infancy.

SUBJECTS AND METHODS

Polysomnographic studies were performed in 32 10-year-old children (13 females and 19 males) who had IDA in infancy and 26 peers (10 females and 16 males) who were nonanemic controls. The time structure of their polysomnographically recorded leg movements (LM) was analyzed by means of an approach particularly able to consider their quantity, periodicity, and distribution during the night.

RESULTS

All LM indexes and those related to periodic LM during sleep (PLMS) were slightly higher in the former IDA group than in the control group, but not always significant. The Periodicity index during NREM sleep was higher and was reflected by a small but significant increase in PLMS separated by 10-50s intervals. PLMS index tended to be higher in former IDA children than in controls throughout the whole night.

CONCLUSION

The association between IDA in infancy, despite iron therapy, and PLMS in childhood could lead to new research in this area. Indeed, transient infantile IDA, a common nutritional problem among human infants, may turn out to be important for understanding the mechanisms of PLMS or restless legs syndrome, which are common in adulthood.

Automated detection of nocturnal slow eye movements modulated by selective serotonin reuptake inhibitors

INTRODUCTION

Eye movements convey important information about brain function. Neuropsychiatric conditions and medications may produce abnormal eye movements (EMs) in sleep. Serotonergic drugs are known to increase nocturnal EMs. Few studies have quantified sleep EMs due to technical complexity. We investigated the effects of serotonergic drugs on slow EMs in sleeping patients using an objective automated EM quantification tool.

METHODS

We studied patients who had polysomnograms for clinical assessment. We identified 5 sertraline, 7 citalopram, and 4 fluoxetine users who were not using other psychoactive medications. Controls were 10 age-matched patients on no medications. An automated objective EM detection tool was developed. The first and last 5 min of each sleep stage were assessed. ANOVA was used to assess the effects of time, stage, and medication.

RESULTS

No differences were noted between SSRI users and controls in demographics. Medications were associated with more slow EMs compared to controls (p<0.05). Among SSRI users, a non-statistical trend was noted for increasing slow EMs in the following pattern: sertraline<citalopram<fluoxetine; this is in keeping with the known serotonergic effects of these SSRIs in pharmacological studies.

CONCLUSIONS

Neurotransmitter effects are reflected in nocturnal EMs during many stages of sleep. Analysis of EMs in sleep may be further developed as an endophenotype for various neuropsychiatric conditions and medication responses.

Restless legs syndrome

Restless legs syndrome (RLS) is characterized by a compelling, often insatiable, need to move the legs, accompanied by unpleasant sensations located mainly in the ankles and calves. Because symptoms are brought on by inactivity, distress intrudes upon everyday, sedentary activities such as plane travel, car rides, and attending school, meetings, or the theatre. Symptoms show a diurnal preference for the evening and night, so disruption of sleep onset or maintenance is particularly common. RLS is associated with both lower ratings of quality of life and higher rates of cardiovascular disease. Four common genetic loci associating to RLS have recently been identified, but the molecular pathways by which they increase risk for RLS have yet to be determined. Both sensory (RLS) and motor (periodic limb movements of sleep) symptoms are responsive to dopaminergic medications, yet clear delineation of dopaminergic pathology has not emerged. Brain iron is reduced in many, but not all, patients with RLS. First-line treatment for RLS includes agents acting at D(2) and D(3) dopamine receptors.

Advances in the science of genomics in restless legs syndrome

Restless legs syndrome (RLS) is a sleep and movement disorder that affects up to 15% of the population across the lifespan. Many health care providers have doubted its validity as an illness and are uncertain as to the implications of health care outcomes. The cause of RLS is unknown. Common treatment options include dopaminergics, benzodiazepines, and opioids; however, the pharmacogenetic mechanisms of treatment are unknown. One of the greatest genetic discoveries in 2007 was the identification of genetic variance associated with RLS. There is, however, a lack of knowledge related to RLS and its genetic basis. Therefore, the purposes of this article are to (a) provide information about the science of clinical care related to RLS; (b) present a systematic review of the literature on the status of genetics/genomics of RLS, including the discovery of associated genetic variance; and (c) identify implications of the current state of the science for health care providers and biobehavioral researchers. With the continuing genetic discoveries in RLS, health care providers, specifically nurses who play a major role in research, genetic counseling, and education, need to understand the implications of this sleep and movement disorder for patients across the lifespan.

Genotyping sleep disorders patients

OBJECTIVE

The genetic susceptibility factors underlying sleep disorders might help us predict prognoses and responses to treatment. Several candidate polymorphisms for sleep disorders have been proposed, but there has as yet inadequate replication or validation that the candidates may be useful in the clinical setting.

METHODS

To assess the validity of several candidate associations, we obtained saliva deoxyribonucleic acid (DNA) samples and clinical information from 360 consenting research participants who were undergoing clinical polysomnograms. Ten single nucleotide polymorphisms (SNPs) were genotyped. These were thought to be related to depression, circadian sleep disorders, sleep apnea, restless legs syndrome (RLS), excessive sleepiness, or to slow waves in sleep.

RESULTS

With multivariate generalized linear models, the association of TEF rs738499 with depressive symptoms was confirmed. Equivocal statistical evidence of association of rs1801260 (the C3111T SNP in the CLOCK gene) with morningness/eveningness and an association of Apolipoprotein E (APOE) rs429358 with the Epworth Sleepiness Scale (ESS) were obtained, but these associations were not strong enough to be of clinical value by themselves. Predicted association of SNPs with sleep apnea, RLS, and slow wave sleep were not confirmed.

CONCLUSION

The SNPs tested would not, by themselves, be of use for clinical genotyping in a sleep clinic.

Children show individual night-to-night variability of periodic limb movements in sleep

STUDY OBJECTIVE

Several studies have documented the occurrence of significant night-to-night variability of periodic limb movements in sleep (PLMS) in adults.The aim of this study was to investigate the night-tonight variability of PLMS in children.

DESIGN AND MEASUREMENTS

Two to 4 nights of polysomnography were performed as part of a multisite, placebo-controlled study investigating the effects of carbidopa/levodopa on attention-deficit/hyperactivity disorder in children who were not taking other medications that impacted the central nervous system. Baseline polysomnograms from all children and endpoint polysomnograms from children who were randomly assigned to a placebo group were scored using International Restless Legs Syndrome Study Group criteria for PLMS. PLMS indexes from 101 sleep studies of 36 children, aged 7 to 12 years, were compared.

INTERVENTIONS

N/A.

RESULTS

For all 36 children as a group, PLMS index on Night 1 was predictive of PLMS index on Night 2 (odds ratio 7.0, 95% confidence interval 1.4-38.4), suggesting that overall diagnostic classification (PLMS index above or below 5/h) was accurate. In addition, for the 15 children with 5 or more PLMS per hour on either night, there was no significant group difference on Night 1 versus Night 2 for mean PLMS index (10.6 vs 8.5/h, P = 0.92) or chance of having 5 or more PLMS per hour, indicating no first-night effect. When looking at individual data, however, 9 of these 15 children (60%) had PLMS indexes over and under the 5 per hour cutoff on these 2 nights. Of these 15, 10 had clinical diagnoses of restless legs syndrome and 5 of periodic limb movement disorder (PLMD). The PLMS indexes of all children who were medication free for a third and fourth night (n = 7) or just a third night (n = 2) and had not shown a PLMS index of 5 or greater on either of the first 2 nights remained under this threshold.

CONCLUSIONS

In this sample of children, considerable individual night-to-night variability of PLMS indexes was observed. This finding has important clinical relevance for the diagnosis of restless legs syndrome and PLMD and may have an impact on future studies that correlate individual PLMS severity with frequently associated symptoms, such as negative affect, fatigue, and inattention. Our data, however, also suggest that individual PLMS variability is random and not likely to skew the group-level analysis of treatment outcome studies.

Pediatric restless legs syndrome and periodic limb movement disorder: parent-child pairs

OBJECTIVE

Although recent publications have reported the occurrence of restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) in children and adolescents, the literature is relatively limited. The goals of this retrospective study were to (1) apply the recent International Classification of Sleep Disorders 2nd edition (ICSD-2) diagnostic criteria for RLS and PLMD in pediatric cases where periodic limb movements in sleep (PLMS) 5 per hour were found; (2) review parental history of RLS; and (3) further define the clinical characteristics of RLS and PLMD in a pediatric subgroup where each child had a parent with clinically assessed RLS.

METHODS

This was a retrospective analysis of consecutive polysomnograms (PSGs) with PLMS >5 per hour in patients 19 years of age from a single pediatric sleep/neurology practice over 11 years. Excluded were cases with sleep apnea, narcolepsy, or medication that might induce or aggravate PLMS or RLS. ICSD-2 diagnostic criteria for definite RLS and PLMD were applied to the pediatric cases, and parental history for RLS was assessed. A subset of cases was included for detailed review if the child or adolescent had RLS or PLMD and a biological parent met RLS criteria and had a formal sleep evaluation.

RESULTS

There were 204 cases that met the initial inclusion criteria. A positive parental history of RLS was found in 53% of pediatric RLS cases and in 52% of pediatric PLMD cases. A subset of 37 children or adolescents and 36 biological parents, from 33 different families, met full inclusion criteria and are presented in detail. Of these 37, 10 had a diagnosis of RLS and 27 a diagnosis of PLMD. Over this same period of time, PLMS >5 per hour were found in 74% of pediatric definite RLS cases assessed by PSG.

CONCLUSIONS

This case series adds to the growing literature describing RLS and PLMD in children and adolescents using recently revised diagnostic criteria. The similar prevalence of parental RLS in both pediatric RLS and pediatric PLMD cases suggests a close association between PLMD and RLS in some cases. This supports the emerging view that PLMS may be a marker or endophenotype for a specific, common RLS genotype.

Empirical evaluation of the accuracy of diagnostic criteria for Restless Legs Syndrome

BACKGROUND

In accordance with the diagnostic criteria of the International Restless Legs Syndrome (RLS) Study Group, the diagnosis of RLS is exclusively based on subjective information. Patients must report an urge to move the legs (and arms) with or without unpleasant sensations which is engendered by rest, relieved by movement, and worse in the evening or at night than during the day (essential criteria). Objective information such as excessive periodic leg movements, positive response to dopaminergic medication, family history of RLS or findings of a neurological examination cannot substitute any of the essential criteria but are considered both supportive for the RLS diagnosis and important for decisions on differential diagnoses. In this article, we report a systematic empirical analysis of the accuracy of diagnostic decisions based on all diagnostic criteria being either "essential" or "non-essential."

METHODS

We re-analyzed data from a validation study for the RLS Diagnostic Index, in which ten items related to diagnostic criteria were compared with an expert diagnosis of RLS (n = 86) and other sleep-related diagnoses (n = 93). The value of individual diagnostic criteria and features of RLS predictive of the expert diagnoses were analyzed with logistic regression models by increasing the set of diagnostic criteria stepwise based on delta-chi(2) tests.

RESULTS

The essential diagnostic criteria share a large amount of variance in the prediction of the expert diagnosis. Three of the four essential criteria (urge to move the legs, which is engendered by rest and worse in the evening) almost completely determine the expert diagnosis. However, adding response to dopaminergic medication to the set of the essential criteria increased the effect size in the logistic regression model from 69.4% to 88.4%, indicating a relevant improvement of the accuracy in supporting or excluding the diagnosis of RLS.

CONCLUSION

On the basis of our exploratory empirical analysis we conclude that the accuracy of diagnostic decision making in patients suspicious for RLS can be improved by inclusion of objective information. Response to dopaminergics is the most important criterion which both supports the "true" diagnosis of RLS, if present, and is also relevant to exclude mimics of RLS.

Ropinirole treatment for restless legs syndrome

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance. Ropinirole, a non-ergot dopamine agonist, has been widely studied for the treatment of moderate-to-severe primary RLS in a comprehensive clinical development program. In these studies, ropinirole was effective in significantly improving the symptoms of RLS, compared with placebo, in patients with moderate-to-severe primary RLS. These improvements are supported by data from individual studies, as well as by pooled analyses. Significant improvements in RLS symptoms were observed within 2 nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements; and on subjective measures of sleep, ropinirole was generally well tolerated. A newly developed extended-release formulation of ropinirole may benefit patients who warrant an extended duration of therapy.

Internal medicine: guidance to the diagnosis and management of restless legs syndrome

Restless legs syndrome (RLS) is a chronic neurologic disorder, with a prevalence rate in the general population of 5% to 10%. The diagnosis of RLS is straightforward; it is based on symptom history alone and uses the four essential diagnostic criteria for RLS. Owing to the heterogeneity of the disorder, the sensory and motor symptoms of RLS are often attributed to other disorders, and many patients remain undiagnosed and untreated. The symptoms of RLS are thought to result from a central dopaminergic dysfunction. Dopamine agonists are considered first-line treatment for moderate-to-severe primary RLS, although other nondopaminergic therapies are sometimes used to ease the symptoms of RLS. This article will guide primary care and internal medicine specialists through the diagnosis and management options of primary RLS.

Ropinirole treatment for restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance.

OBJECTIVE

Prepare a drug evaluation of the non-ergot dopamine agonist ropinirole in RLS.

METHODS

Review of scientific literature on RLS, particularly focusing on treatment with ropinirole.

CONCLUSION

Ropinirole has been studied for treatment of moderate to severe primary RLS in a comprehensive clinical development program. Ropinirole significantly improved symptoms of RLS, versus placebo, in patients with primary RLS. These improvements are supported by data from individual studies and pooled analyses. Significant improvements in RLS symptoms were observed within two nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements, and subjective measures of sleep. Ropinirole was generally well tolerated.

Update of the pathophysiology of the restless-legs-syndrome

The Restless Legs Syndrome (RLS) is a heterogeneous disease. Symptomatic or secondary forms encompass iron deficiency, uremia, pregnancy, polyneuropathy, and other causes. The so-called idiopathic RLS syndrome preferentially affects patients with a younger onset before the age of 30. Here we summarize pathophysiological results along the anatomical route, beginning at the cortex and followed by the basal ganglia, thalamus, A11 neurones, substantia nigra, brainstem nuclei, and spinal cord. Genetic risk variants for RLS have recently been identified in two genes, one of them the homeobox gene MEIS1, known to be involved in embryonic development and variants in a second locus containing the genes encoding mitogen-activated protein kinase MAP2K5, and the transcription factor LBXCOR1. A third one, the BTBD9 gene with unknown function encodes a BTB(POZ) domain. Accordingly, new concepts on pathophysiology have to bridge conventional knowledge with possible consequences deriving from these findings. Furthermore, this may create a framework to help understand why dopamine, opioid, and some anticonvulsant therapies are effective in RLS patients.

Clinical significance of RLS

While the restless legs syndrome (RLS) may have been known in antiquity, it has only recently come to medical attention. Individuals with RLS fall along a spectrum from mild, infrequent symptoms to those with severe daily life-impairing discomforts and sleep disruption. These problems can cause impaired mood, daytime fatigue, cognitive difficulties, and inability to participate in a variety of quiet activities. This leads to a general reduction in quality of life similar to other significant psychiatric and medical disorders. Recent studies suggest that RLS may be a risk factor for developing both psychiatric disorders (such as major depression and anxiety) and somatic diseases (such as hypertension and cardiovascular disease). In dialysis patients, RLS has been found to be a risk factor for mortality. Therefore, those with RLS who have clinically significant symptoms suffer increased morbidity and are at risk for impaired long-term medical outcomes.