Periodic leg movements are associated with reduced sleep quality in older men: the MrOS Sleep Study

Restless Legs Syndrome and Periodic Limb Movements of Sleep: From Neurophysiology to Clinical Practice

SUMMARY

This article summarizes restless legs syndrome (RLS), periodic limb movements of sleep, and periodic limb movement disorder. RLS is a common sleep disorder with a prevalence of 5% to 15% in the general population. RLS can present in childhood, and incidence increases with age. RLS can be idiopathic or secondary to iron deficiency, chronic renal failure, peripheral neuropathy, and medications such as antidepressants (with higher rates for mirtazapine and venlafaxine, while bupropion may reduce symptoms at least in the short term), dopamine antagonists (neuroleptic antipsychotic agents and antinausea medications), and possibly antihistamines. Management includes pharmacologic agents (dopaminergic agents, alpha-2 delta calcium channel ligands, opioids, benzodiazepines) and nonpharmacologic therapies (iron supplementation, behavioral management). Periodic limb movements of sleep are an electrophysiologic finding commonly accompanying RLS. On the other hand, most individuals with periodic limb movements of sleep do not have RLS. The clinical significance of the movements has been argued. Periodic limb movement disorder is a distinct sleep disorder that arises in individuals without RLS and is a diagnosis of exclusion.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

Management of Sleep Disturbances in Parkinson's Disease

Parkinson's disease (PD) is defined by its motor symptoms rigidity, tremor, and akinesia. However, non-motor symptoms, particularly autonomic disorders and sleep disturbances, occur frequently in PD causing equivalent or even greater discomfort than motor symptoms effectively decreasing quality of life in patients and caregivers. Most common sleep disturbances in PD are insomnia, sleep disordered breathing, excessive daytime sleepiness, REM sleep behavior disorder, and sleep-related movement disorders such as restless legs syndrome. Despite their high prevalence, therapeutic options in the in- and outpatient setting are limited, partly due to lack of scientific evidence. The importance of sleep disturbances in neurodegenerative diseases has been further emphasized by recent evidence indicating a bidirectional relationship between neurodegeneration and sleep. A more profound insight into the underlying pathophysiological mechanisms intertwining sleep and neurodegeneration might lead to unique and individually tailored disease modifying or even neuroprotective therapeutic options in the long run. Therefore, current evidence concerning the management of sleep disturbances in PD will be discussed with the aim of providing a substantiated scaffolding for clinical decisions in long-term PD therapy.

Individual periodic limb movements with arousal are temporally associated with nonsustained ventricular tachycardia: a case-crossover analysis

STUDY OBJECTIVES

Both periodic limb movements during sleep (PLMS) and arousals are associated with sympathetic nervous system activation and may be arrhythmogenic. We hypothesize a temporal relationship exists between individual PLMS, particularly with arousal, and nonsustained ventricular tachycardia (NSVT) events.

METHODS

A bidirectional time-stratified case-crossover design was used to assess temporal associations between PLMS and NSVT during sleep in 49 Osteoporotic Fractures in Men Sleep Study participants with NSVT in a community-based cohort (n = 2,911). Sleep time was divided into approximate 30-min segments. For each NSVT (n = 141), we selected a preceding 30-s hazard period and three randomly chosen 30-s control periods from sleep within the same segment and evaluated for PLMS, respiratory events, minimum saturation, and arousals. Odds ratios and 95% confidence intervals-OR (95% CI)-were determined by conditional logistic regression; covariates included EEG arousals, minimum saturation, and respiratory events in the same hazard/control period.

RESULTS

Participants with NSVT were 79.5 ± 6.2 years with a PLMS index of 32.1 (IQR: 10.1, 61.4) and apnea-hypopnea index of 17.1 (IQR: 9.4, 26.1). PLMS without arousal were not significantly associated with NSVT (OR = 0.80, 95% CI: 0.41-1.59). PLMS with arousal were associated with NSVT in unadjusted analyses (OR = 2.50, 95% CI: 1.11-5.65) and after adjustment (OR = 2.31, 95% CI: 1.02-5.25). Arousals associated with PLMS were associated with NSVT in unadjusted (OR = 2.84, 95% CI: 1.23-6.56) and adjusted analyses (OR = 2.61, 95% CI: 1.13-6.05).

CONCLUSIONS

PLMS with (but not without) arousals are temporally associated with a greater than twofold higher odds of subsequent NSVT episodes. PLMS-related arousals may be physiologically important ventricular arrhythmia triggers.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT00070681.

Mechanism of excessive wake time when associated with obstructive sleep apnea or periodic limb movements

STUDY OBJECTIVES

It is uncertain whether obstructive apnea (OSA) or periodic limb movements (PLMs) contribute to excessive wake time (EWT) when EWT and these disorders coexist. We hypothesized that such EWT is an independent disorder related to central regulation of sleep depth. Accordingly, we compared sleep depth in patients with EWT and OSA/PLMs (EWT+P) with patients with EWT and no OSA/PLMs (EWT-NP) and patients with a normal wake time.

METHODS

A total of 267 participants were divided into five groups: (1) EWT+P: n = 100 (wake time > 20% total recording time; TRT) with OSA (apnea-hypopnea index 5-110 events/h) and/or PLMs (PLM index 10-151 events/h); (2) EWT-NP: n = 49 (wake time > 20%TRT), no associated pathology; (3) normal wake time (NWT)+P: n = 54 (wake time < 20%TRT, with OSA/PLMs); (4) NWT-NP: n = 26; (5) Healthy participants: n = 38 (no sleep complaints, NWT and no OSA/PLMs). Sleep depth was evaluated by the odds ratio product (ORP; 0 = deep sleep, 2.5 = fully alert). We also measured ORP in the 9 seconds immediately following arousals (ORP-9) to distinguish between peripheral and central mechanisms of light sleep.

RESULTS

ORP during sleep was higher (lighter sleep) in both EWT groups than in the three NWT groups (P < 1E-11) with no difference between those with and those without OSA/PLMs. ORP-9 was also significantly higher in the EWT groups than in the NWT groups (P < 1E-19), also with no difference between those with and without OSA/PLMs, indicating that the lighter sleep was of central origin. There were highly significant correlations between wake time and ORP-9 across all groups (P < 1E-35).

CONCLUSIONS

EWT associated with OSA/PLMs is independent of OSA/PLMs and related to abnormal central regulation of sleep depth.

Advanced Circadian Timing and Sleep Fragmentation Differentially Impact on Memory Complaint Subtype in Subjective Cognitive Decline

BACKGROUND

Increased sleep fragmentation and advanced circadian timing are hallmark phenotypes associated with increased age-related cognitive decline. Subjective cognitive decline (SCD) is considered a prodromal stage of neurodegeneration and dementia; however, little is known about how sleep and circadian timing impact on memory complaints in SCD.

OBJECTIVE

To determine how sleep and circadian timing impact on memory complaint subtypes in older adults with SCD.

METHODS

Twenty-five older adults with SCD (mean age = 69.97, SD = 5.33) completed the Memory Functioning Questionnaire to characterize their memory complaints. They also underwent neuropsychological assessment, and completed 1 week of at-home monitoring of sleep with actigraphy and sleep diaries. This was followed by a two-night laboratory visit with overnight polysomnography and a dim light melatonin onset assessment to measure circadian timing.

RESULTS

Advanced circadian timing was associated with greater memory complaints, specifically poorer memory of past events (r = -0.688, p = 0.002), greater perceived decline over time (r = -0.568, p = 0.022), and increased reliance on mnemonic tools (r = -0.657, p = 0.004). Increased sleep fragmentation was associated with reduced self-reported memory decline (r = 0.529, p = 0.014), and reduced concern about everyday forgetfulness (r = 0.435, p = 0.038).

CONCLUSION

Advanced circadian timing was associated with a number of subjective memory complaints and symptoms. By contrast, sleep fragmentation was linked to lowered perceptions of cognitive decline, and less concern about memory failures. As circadian disruption is apparent in both MCI and Alzheimer's disease, and plays a key role in cognitive function, our findings further support a circadian intervention as a potential therapeutic tool for cognitive decline.

Associations between sleep and verbal memory in subjective cognitive decline: A role for semantic clustering

Age-related reductions in slow wave activity (SWA) and increased fragmentation during sleep play a key role in memory impairment. As the prefrontal cortex is necessary for the control processes relevant to memory encoding, including utilisation of internal heuristics such as semantic clustering, and is preferentially vulnerable to sleep disturbance, our study examined how SWA and sleep fragmentation relates to memory performance in individuals with Subjective Cognitive Decline (SCD). Thirty older adults with SCD (Mean Age = 69.34, SD = 5.34) completed a neurocognitive test battery, including the California Verbal Learning Test, which was used to assess semantic clustering. One week later, participants were admitted to the laboratory for a two night visit. SWA and sleep fragmentation were captured using sleep polysomnography. Next-day memory performance was tested using the Rey Auditory Verbal Learning Test. Poorer sleep (reduced SWA; increased arousals) was associated with reduced semantic clustering, which mediated impairment on verbal memory and learning tests conducted both the day after sleep was recorded (for both SWA and arousals), and a week prior (for arousals only). We demonstrate semantic clustering mediated the well described associations between sleep and verbal memory. As these strategies are a component of cognitive training interventions, future research may examine the role of simultaneous sleep interventions for improving cognitive training outcomes.

Objective napping, cognitive decline, and risk of cognitive impairment in older men

INTRODUCTION

Little is known about the longitudinal association between napping and cognitive impairment in older adults.

METHODS

We used wrist actigraphy to measure naps in 2751 community-dwelling older men. Cognition was assessed repeatedly over 12 years, and clinically significant cognitive impairment was determined by physician diagnosis, Alzheimer's medication use or a significant cognitive decline.

RESULTS

After adjustment for all covariates, men with longer napping duration had greater cognitive decline and higher risk of cognitive impairment. Men who napped for ≥120 min/day (vs. <30 min/day) were 66% more likely to develop cognitive impairment (odds ratio = 1.66, 95% CI: 1.09-2.54) in 12 years. Further adjustment for nighttime sleep quality did not appreciably alter the results. The association between napping and cognitive impairment was more pronounced among those with higher sleep efficiency and average sleep duration.

DISCUSSION

Napping might be useful as an early marker of cognitive impairment in the elderly, and its cognitive effects may differ by nighttime sleep.

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.

Excessive daytime sleepiness, objective napping and 11-year risk of Parkinson's disease in older men

Background

It is unknown whether subjective daytime sleepiness or objective napping could precede the risk of Parkinson's disease (PD) in the long term.

Methods

We studied 2920 men (mean age 76 years) without a history of PD and followed them for 11 years. Excessive daytime sleepiness (EDS) was defined as having an Epworth Sleepiness Scale score >10. Objective naps were defined as ≥5 consecutive minutes of inactivity as measured by actigraphy, and napping duration was the accumulated time of naps outside the main sleep period. We used logistic regression to compare PD risk across four groups: no EDS& napping <1 h/day (N = 1739, 59.5%; referent group), EDS& napping <1 h/day (N = 215, 7.4%), no EDS& napping ≥ 1 h/day (N = 819, 28.1%) and EDS& napping ≥ 1 h/day (N = 147, 5.0%).

Results

We identified 106 incident PD cases over 11 years. After multivariable adjustment, men with napping  ≥  1h/day alone were twice as likely [odds ratio (OR) = 1.96, 95% confidence interval (CI) 1.25-3.08], and men with both EDS and napping  ≥ 1 h/day were almost three times as likely to develop PD (2.52, 1.21-5.27), compared with the referent group. Compared with those with naps for <30 min, men who napped for  ≥1 h/day had more than double the risk of PD. No association was found for EDS alone and PD risk. Further adjustment for chronotype and circadian stability, or excluding PD cases identified within 2 years after napping measurements, showed similar results.

Conclusions

Objective long napping rather than subjective EDS was prospectively associated with a higher risk of PD in older men. Objective measures of napping might be valuable as a preclinical marker for PD.

Periodic limb movements in sleep: Prevalence and associated sleepiness in the Wisconsin Sleep Cohort

OBJECTIVES

Periodic limb movements in sleep (PLMS) are thought to be prevalent in elderly populations, but their impact on quality of life remains unclear. We examined the prevalence of PLMS, impact of age on prevalence, and association between PLMS and sleepiness.

METHODS

We identified limb movements in 2335 Wisconsin Sleep Cohort polysomnograms collected over 12 years. Prevalence of periodic limb movement index (PLMI) ≥15 was calculated at baseline (n = 1084). McNemar's test assessed changes in prevalence over time. Association of sleepiness and PLMS evaluated using linear mixed modeling and generalized estimating equations. Models adjusted for confounders.

RESULTS

Prevalence of PLMI ≥15 at baseline was 25.3%. Longitudinal prevalence increased significantly with age (p = 2.97 × 10^-14). Sleepiness did not differ significantly between PLMI groups unless stratified by restless legs syndrome (RLS) symptoms. The RLS+/PLM+ group was sleepier than the RLS+/PLM- group. Multiple Sleep Latency Test trended towards increased alertness in the RLS-/PLM+ group compared to RLS-/PLM-.

CONCLUSIONS

A significant number of adults have PLMS and prevalence increased with age. No noteworthy association between PLMI category and sleepiness unless stratified by RLS symptoms.

SIGNIFICANCE

Our results indicate that RLS and PLMS may have distinct clinical consequences and interactions that can help guide treatment approach.

Associations of Incident Cardiovascular Events With Restless Legs Syndrome and Periodic Leg Movements of Sleep in Older Men, for the Outcomes of Sleep Disorders in Older Men Study (MrOS Sleep Study)

Study Objectives

Both restless legs syndrome (RLS) and periodic leg movements in sleep (PLMS) may be associated with incident cardiovascular disease (CVD). However, the individual contributions of these factors to adverse CVD outcomes are unknown.

Methods

During the MrOS Sleep Study, 2823 men (mean age = 76.3 years) participated in a comprehensive sleep assessment from 2000 to 2002. RLS was identified by self-report of a physician diagnosis of RLS. A periodic limb movement of sleep index (PLMI) was derived from unattended in-home polysomnography. Incident cardiovascular events were centrally adjudicated during 8.7 ± 2.6 years of follow-up. The primary outcome was all-cause CVD; secondary outcomes included incident myocardial infarction (MI) and cerebrovascular disease. Cox proportional hazards regression models were adjusted for multiple covariates, including PLMI, to examine if there were independent associations of RLS and PLMI to the outcomes.

Results

Physician-diagnosed RLS was reported by 2.2% and a PLMI ≥ 15 was found in 59.6% of men. RLS was not associated with the composite CVD outcome. RLS was significantly associated with incident MI (Hazard ratio [HR] = 2.02, 95% CI, 1.04-3.91) even after adjustment for multiple covariates. Results were only modestly attenuated when PLMI was added to the model. PLMI also was found to predict incident MI (per SD increase in PLMI, HR = 1.14, 95% CI, 1.00-1.30, p = .05), and was materially unchanged after addition of RLS.

Conclusions

The independent risk that RLS confers for MI suggests a role for non-PLMS factors such as sleep disturbance, shared genetic factors, or PLM-independent sympathetic hyperactivity.

The Treatment of Sleep Disorders in Parkinson's Disease: From Research to Clinical Practice

Sleep disorders (SDs) are one of the most frequent non-motor symptoms of Parkinson’s disease (PD), usually increasing in frequency over the course of the disease and disability progression. SDs include nocturnal and diurnal manifestations such as insomnia, REM sleep behavior disorder, and excessive daytime sleepiness. The causes of SDs in PD are numerous, including the neurodegeneration process itself, which can disrupt the networks regulating the sleep–wake cycle and deplete a large number of cerebral amines possibly playing a role in the initiation and maintenance of sleep. Despite the significant prevalence of SDs in PD patients, few clinical trials on SDs treatment have been conducted. Our aim is to critically review the principal therapeutic options for the most common SDs in PD. The appropriate diagnosis and treatment of SDs in PD can lead to the consolidation of nocturnal sleep, the enhancement of daytime alertness, and the amelioration of the quality of life of the patients.

Periodic Limb Movements in Sleep are Associated with Greater Cognitive Decline in Older Men without Dementia

STUDY OBJECTIVES

To examine the association between periodic limb movements in sleep (PLMS) and change in selected aspects of cognition in community-dwelling older men.

METHODS

We studied 2,636 older men without dementia who underwent in-home polysomnography with measurement of the periodic limb movement index (PLMI) and periodic limb movement arousal index (PLMAI) using piezoelectric sensors. Random-effects models and logistic regression were used to examine the association between PLMI, PLMAI, and 3- to 4-y change in cognition.

RESULTS

After multivariable adjustment, men with a high PLMI had greater decline on the Trail Making Test - Part B (P trend = 0.02); those with a PLMI ≥ 30 were 48% more likely (odds ratio = 1.48, 95% confidence interval = 1.05-2.07) to experience the development of significant cognitive impairment (≥ 1 SD above mean change). Further adjustment for sleep efficiency, nocturnal hypoxemia, or dopaminergic medication use and analysis among men without Parkinson disease (n = 2,607) showed similar findings. No significant association was found for PLMAI or for Modified Mini-Mental State Examination scores.

CONCLUSIONS

Among older men without dementia, higher PLMS frequency was associated with greater decline in cognition, particularly in executive function.

Longitudinal relationships of periodic limb movements during sleep and incident atrial fibrillation

OBJECTIVES

This study aimed to examine relationship between periodic limb movements during sleep (PLMS) and incident atrial fibrillation/flutter (AF).

METHODS

Prospective multicenter cohort (n = 2273: adjudicated AF group; n = 843: self-reported AF group) of community-dwelling men without prevalent AF were followed for an average of 8.3 years (adjudicated) and 6.5 years (self-reported). PLMS index (PLMI, <5 (ref), ≥5 to <30, ≥30) and PLM arousal index (PLMAI, <1 (ref), ≥1 to <5, ≥5) were measured by polysomnography. Incident adjudicated and self-reported AF were analyzed by Cox proportional hazards and logistic regression, respectively, and adjusted for age, clinic, race, body mass index (BMI), alcohol use, cholesterol level, cardiac medications, pacemaker, apnea-hypopnea index, renal function, and cardiac risk. The interaction of age and PLMS was examined.

RESULTS

In this primarily Caucasian (89.8%) cohort of older men (mean age 76.1 ± 5.5 years) with BMI of 27.2 ± 3.7, there were 261 cases (11.5%) of adjudicated and 85 cases (10.1%) of self-reported incident AF. In the overall cohort, PLMI and PLMAI were not associated with adjudicated or self-reported AF. There was some evidence of an interaction of age and PLMI (p = 0.08, adjudicated AF) and PLMAI (p ≤ 0.06, both outcomes). Among men aged ≥76 years, the highest PLMI tertile was at increased risk of adjudicated AF (≥30 vs. <5; hazard ratio (HR) = 1.63, 1.01-2.63) and the middle PLMAI tertile predicted increased risk of both outcomes (1 to <5 vs. <1; adjudicated, HR = 1.65, 1.05-2.58; self-reported HR = 5.76, 1.76-18.84). No such associations were found in men aged <76 years.

CONCLUSIONS

Although PLMS do not predict AF incidence in the overall cohort, the findings suggest PLMS increases incident AF risk in the older subgroup.

Sleep architecture alterations in patients with periodic limb movements disorder during sleep and sleep breathing disorders

Introduction

Sleep movement disorders includes mainly periodic limb movement and others. The more frequent breathing disorders are: obstructive sleep apnea-hypopnea syndrome and primary snoring.

Objective

To compare sleep architecture in periodic limb movements and breathing disorders of different severity, and weight their interactions.

Methods

We compared sleep architecture in 160 patients, divided in six groups: periodic limb movements (n=25), obstructive apnea only (n=30), periodic limb movements/snoring (n=30), periodic limb movements/mild apnea (n=25), periodic limb movements/moderate apnea (n=25), periodic limb movements/severe apnea (n=26). Polysomnographic variables were compared by analysis of variance and Tukey test.

Results

We observed an increase of percentage of awakenings in the group with periodic limb movements/severe apnea. We found an increase of percentage of light sleep in the group with obstructive apnea only with respect to periodic limb movements group. The group with obstructive apnea only presented less rapid eye movements sleep in relation with group with periodic limb movements. We found an increase of awakenings in the group with periodic limb movements/severe apnea to the group with periodic limb movements only. Oxygen saturation showed a decrease in the group with periodic limb movements/severe apnea and obstructive apnea only group to periodic limb movements only group.

Conclusions

Periodic limb movements and breathing disorders, resulted in more additive changes in sleep architecture alterations, than as separately disorders, in a complex interaction. Research in these relations deserve more investigations.

Polysomnographic Study of Sleep in Survivors of Breast Cancer

STUDY OBJECTIVE

Insomnia is a frequent complaint in breast cancer patients during and after treatment. Breast cancer survivors, 1-10 years posttreatment, underwent in-lab polysomnography (PSG) to objectively define the insomnia in those patients with such a complaint.

METHODS

Twenty-six breast cancer survivors (aged 39-80, mean 54.0 months posttreatment) spent 2 nights in the sleep laboratory. Sleep on Night 2 was scored for sleep stages, sleep onset latency, REM sleep onset latency, wake time, apneas and hypopneas, periodic limb movements and arousals. Subjects were allocated into 2 groups by their scores on the Pittsburgh Sleep Quality Index (PSQI): no/ mild sleep disturbance (PSQI score ≤ 9, n = 15) or moderate/ severe sleep disturbance (PSQI ≥ 10, n = 11).

RESULTS

Standard PSG/EEG parameters failed to differentiate insomniacs from non-insomniacs. The single variable that distinguished the insomnia group was periodic limb movements in sleep (PLMS). PLMS were significantly correlated (r ≅ 0.7, p < 0.02) with subjective report of insomnia on PSQI and insomnia severity index. Log[Number of PLMS] was higher in the moderate/severe insomnia group (p = 0.008). Five of 11 patients in the moderate/severe insomnia group had a PLMS index ≥ 15, compared to only one of 15 patients in the none/mild insomnia group (p = 0.02). Menopausal symptoms and use of caffeine, hypnotics, and antidepressants were unrelated to insomnia severity or PLMS.

CONCLUSIONS

PLMS was the sole PSG variable that separated breast cancer survivors with moderate/severe insomnia from those with no/mild sleep disturbance. Further study of the incidence and significance of PLMS in breast cancer survivors with the complaint of insomnia is merited.

Prevalence and associations of respiratory-related leg movements: the MrOS sleep study

OBJECTIVES

Obstructive respiratory events often terminate with an associated respiratory-related leg movement (RRLM). Such leg movements are not scored as periodic leg movements (periodic limb movements during sleep, PLMS), although the criteria for distinguishing RRLM from PLMS differ between the American Academy of Sleep Medicine (AASM) and the World Association of Sleep Medicine (WASM)/ International Restless Legs Syndrome Study Group (IRLSSG) scoring manuals. Such LMs may be clinically significant in patients with obstructive sleep apnea (OSA). The prevalence and correlation of RRLM in men with OSA were examined.

METHODS

A case-control sample of 575 men was selected from all men with an apnea-hypopnea index (AHI, ≥3% desaturation criteria) ≥ 10 and good data from piezoelectric leg movement sensors at the first in-home sleep study in the MrOS cohort (mean age = 76.8 years). Sleep studies were rescored for RRLMs using five different RRLM definitions varying in both latency of leg movement onset from respiratory event termination and duration of the leg movement. The quartile of RRLM% (the number of RRLM/the number of hypopneas + apneas) was derived.

RESULTS

The nonparametric densities of RRLM% were most influenced by alterations in the latency rather than the duration of the LM. The most liberal RRLM definition (latency 0-5 s, duration 0.5-10 s) led to a median RRLM% of 23.4 (interquartile range 12.41, 37.12) in this sample. The average AHI and arousal index increased as the quartile of RRLM% increased, as well as the prevalence of chronic obstructive pulmonary disease (COPD). The prevalence of those with a history of hypertension decreased as RRLM% increased. The non-Caucasian race was associated with lower RRLM%.

CONCLUSION

Within an elderly sample with moderate to severe OSA, piezoelectric-defined RRLM% is associated with a number of sleep-related and demographic factors. Further study of the optimal definition, predictors, and consequences of RRLM is warranted.

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.

Association of low ferritin with PLM in the Wisconsin Sleep Cohort

OBJECTIVE

The origins of periodic leg movements (PLMs), a strong correlate of restless legs syndrome (RLS), are uncertain. This study was performed to assess the relationship between PLMs and peripheral iron deficiency, as measured with ferritin levels corrected for inflammation.

METHODS

We included a cross-sectional sample of a cohort study of 801 randomly selected people (n = 1008 assays, mean age 58.6 ± 0.3 years) from Wisconsin state employee agencies. A previously validated automatic detector was used to measure PLMs during sleep. The patients were categorized into RLS symptoms-positive and RLS symptoms-negative based on a mailed survey response and prior analysis. Analyses were performed using a linear model with PLM category above and below 15 PLM/h (periodic leg movement index, PLMI) as the dependent variable, and adjusting for known covariates, including previously associated single-nucleotide polymorphisms (SNPs) within BTBD9, TOX3/BC034767, MEIS1, MAP2K5/SKOR1, and PTPRD. Ferritin and C-reactive protein (CRP) levels were measured in serum, and ferritin levels corrected for inflammation using CRP levels.

RESULTS

After controlling for cofactors, PLMI ≥ 15 was associated with low (≤50 ng/mL) ferritin levels (OR = 1.55, p = 0.020). The best model was found using quasi-least squares regression of ferritin as a function of PLMI, with an increase of 0.0034 PLM/h predicted by a decrease of 1 ng/mL ferritin (p = 0.00447).

CONCLUSIONS

An association was found between low ferritin and greater PLMs in a general population of older adults, independent of genetic polymorphisms, suggesting a role of low iron stores in the expression of these phenotypes. Patients with high PLMI may require to be checked for iron deficiency.

A systematic assessment of the association of polysomnographic indices with blood pressure: the Multi-Ethnic Study of Atherosclerosis (MESA)

STUDY OBJECTIVE

Blood pressure (BP) may be adversely affected by a variety of sleep disturbances, including sleep fragmentation, hypoxemia, respiratory disturbances, and periodic limb movements. We aim to identify which polysomnography indices are most strongly and consistently associated with systolic and diastolic blood pressure (SBP, DBP) levels in a population-based sample.

DESIGN

Cross-sectional analysis of data from 2,040 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) who underwent polysomnography at MESA Exam 5 in 2011-2013.

SETTING

Multisite cohort study.

PARTICIPANTS

Participants were mean age 68 y (54% females; 28% African American, 24% Hispanic, 11% Chinese).

MEASUREMENTS

Thirty-two candidate polysomnography predictors were identified representing the domains of breathing disturbance frequency, hypoxemia, sleep architecture, and periodic limb movements. Cluster analysis was used for variable reduction. Statistical models, adjusted for potential confounders, were derived using stepwise regression. Final models were selected using cross-validation techniques.

RESULTS

The apnea-hypopnea index (AHI) defined using a 4% desaturation hypopnea criterion (AHI4P) was most consistently associated with SBP level. The AHI and periodic limb movement index (associated with arousals; PLMIA) were significantly associated with DBP. Estimated adjusted differences in SBP and DBP levels between an individual with no sleep apnea (AHI4P = 0) and one with moderately severe sleep apnea (AHI4P = 30) were 2.2 mm Hg and 1.1 mm Hg, respectively. Each 10-unit increase in the PLMIA was associated with an increase in DBP of 1.2 mm Hg.

CONCLUSION

Our results support the use of a currently recommended apnea-hypopnea index definition as a marker of blood pressure risk and indicate that measurement of limb movements with arousals is also independently associated with diastolic blood pressure.