Higher Prevalence of Periodic Limb Movements of Sleep in Patients with History of Stroke
ABSTRACT
Study Objectives:
The association between obstructive sleep apnea and stroke is well established. Less is known about the relationship between stroke and periodic limb movements of sleep (PLMS). This study sought to assess the frequency of PLMS in patients with a history of stroke.
Methods:
We reviewed the medical and polysomnographic records of 40 patients with a history of stroke and 40 control patients matched for age, sex, and risk factors.
Results:
19 patients with a history of stroke (47.5%) and 5 control patients (12.5%) had a PLMS index > 5/h (p < 0.001). The average PLMS index was also lower in control patients than patients with stroke (1.9 ± 0.7 and 11.7 ± 3.4; p = 0.006).
Conclusions:
Our patients with a history of stroke had a greater prevalence and severity of PLMS than control patients. These limb movements may have implications for secondary stroke prevention as well as stroke recovery.
Citation:
Coelho FMS; Georgsson H; Narayansingh M; Swartz RH; Murray BJ. Higher prevalence of periodic limb movements of sleep in patients with history of stroke. J Clin Sleep Med 2010;6(5):428-430.
INTRODUCTION
The association between sleep disorders and stroke is gaining recognition.1,2 Obstructive sleep apnea (OSA) is an independent risk factor for stroke and can complicate rehabilitation.3 Prompt treatment of OSA may prevent recurrence and facilitate recovery from stroke.4,5
BRIEF SUMMARY
Current Knowledge/Study Rationale: Periodic limb movements have been associated with blood pressure elevations which may contribute to the finding that restless legs syndrome is associated with an increased risk of cardiovascular disease. This study assessed whether periodic limb movements were more common in patients with a history of stroke.
Study Impact: Clinicians should be aware that periodic limb movements are more common in patients with a history of stroke. Further work is warranted to establish if treatment of periodic limb movements may help with prevention of stroke, and improve rehabilitation outcomes.
Less consideration has been given to other sleep problems, such as restless legs syndrome (RLS) and the closely associated periodic limb movements of sleep (PLMS). PLMS can cause repeated transient blood pressure elevations.6 These may be a contributor to the approximate doubling of cardiovascular risk seen in individuals with RLS.7,8
The pathophysiology of PLMS is not completely understood, but involves abnormalities of aminergic systems, with insufficient central dopamine.7,9 Anatomic substrates for PLMS have been suggested from pontine and lenticulostriate infarctions.10,11 PLMS can thus emerge as a consequence of stroke, but may also be a stroke risk factor.
The goal of this study was to compare the prevalence of PLMS in patients with a history of stroke to a group of control patients. We hypothesized that PLMS would be increased in patients with stroke.
METHODS
Polysomnographic data was collected from patients attending the Sunnybrook Hospital Sleep Laboratory between 2004 and 2009. The institutional research ethics board approved the protocol and patients provided informed consent. Patients were referred for a variety of reasons (commonly sleep apnea). Out of 735 individuals who answered a health questionnaire given to all those attending the sleep laboratory, we identified 40 with a self-reported history of stroke and assessed their existing polysomnographic data. Forty control patients were individually selected by matching for age, sex, and confounds such as diabetes, hypertension, polyneuropathy, anemia, antidepressants, fatigue, RLS, sleep apnea, and snoring.
All stroke and control patients had undergone conventional polysomnography.12 Periodic limb movements and the periodic limb movement index were scored according to American Academy of Sleep Medicine standards. A nasal pressure transducer was used to assess airway resistance, thereby helping ensure limb movements were not arousal responses to subtle respiratory events.
Variable normality was verified. The χ2 test or Fisher test was used to compare qualitative variables. The t-test for independent samples was used to compare quantitative variables. Statistical significance was considered when p < 0.05 with Bonferroni correction for our total of 8 sleep variable comparisons (p < 0.00625).
RESULTS
Clinical and sleep characteristics are summarized in Table 1. Sleep physiology variables including apnea severity were not different between groups. None of the study subjects reported taking dopaminergic medications.
Control patients | Stroke patients | p | |
---|---|---|---|
Age | 63.4 ± 1.7 | 63.3 ± 1.9 | 0.9 |
Sex (% female) | 12 (30%) | 12 (30%) | 1.0 |
Diabetes | 8 (20%) | 10 (25%) | 0.6 |
Hypertension | 19 (47.5%) | 26 (65%) | 0.1 |
Polyneuropathy | 3 (7.5%) | 2 (5%) | 0.6 |
Anemia | 2 (5%) | 2 (5%) | 1.0 |
Antidepressants | 12 (30%) | 13 (32.5%) | 0.9 |
Fatigue | 12 (30%) | 19 (47.5%) | 0.1 |
Restless legs | 7 (17.5%) | 12 (30%) | 0.2 |
Patients with apnea hypopnea index > 5 | 26 (65%) | 26 (65%) | 1.0 |
Snoring | 23 (57.5%) | 24 (55%) | 0.8 |
Sleep efficiency (%) | 69.2 ± 3.1 | 66.7 ± 3.3 | 0.5 |
NREM (%) | 86.6 ± 1.4 | 87.7 ± 1.5 | 0.6 |
REM (%) | 13.4 ± 1.4 | 12.3 ± 1.5 | 0.6 |
AHI (events/h) | 20.6 ± 4.3 | 14.4 ± 2.7 | 0.2 |
Lowest oxygen (%) | 83.0 ± 1.5 | 84.0 ± 1.4 | 0.6 |
PLMS arousal index | 0.6 ± 0.2 | 1.5 ± 0.6 | 0.1 |
PLMS index | 1.9 ± 0.7 | 11.7 ± 3.4 | 0.006 |
Patients with PLMS index > 5 | 5 (12.5%) | 19 (47.5%) | < 0.001 |
Five control patients (12.5%) and 19 stroke patients (47.5%) had > 5 PLMS per hour (p < 0.001). The average PLMS index was lower in controls than stroke patients (1.9 ± 0.7 and 11.7 ± 3.4; p = 0.006).
DISCUSSION
The major finding of this study was a higher prevalence of PLMS in patients with a history of stroke referred to a sleep laboratory for assessment of sleep problems compared to subjects referred to a sleep laboratory without stroke. The stroke group also had more patients with RLS, although this was not statistically significant. The groups were matched for conditions and medications known to influence the occurrence of RLS and PLMS.13 The relative contribution of these two phenomena to increased cardiovascular risk is currently unknown.
Potential weaknesses of the study include the self-reporting of conditions and medications, including stroke. This study is also limited by its retrospective design (though patient data was acquired prospectively), especially in terms of the lack of information regarding stroke location, timing, and outcomes. Although we did not have iron studies of our patients, the self-reporting of anemia was equal between the groups.
Strengths of this study include a relatively large polysomnographic sample, and objective sleep data. PLMS and OSA can occur together and some have noted that respiratory problems may precipitate PLMS.14 Our study took into consideration upper airway resistance to exclude movements related to subtle respiratory events. Our groups were matched for apnea severity; sleep disordered breathing would thus not account for the PLMS differences that we found. We believe this study is representative of an ambulatory post-stroke population. For example, the prevalence of OSA is similar to other unselected study populations.4
Under-diagnosis of PLMS in the post-stroke population may undermine antihypertensive efforts and increase the stroke recurrence risk.7,15 Very few limb movements in our study were associated with visually scored arousals and therefore patients may be relatively asymptomatic. Improving sleep quality through treatment of underlying sleep disorders could well be important to stroke rehabilitation and may represent an independent treatment target.4
In conclusion, this study demonstrated a higher prevalence of PLMS in our patients with a history of stroke compared to control patients. Prospective studies are needed to confirm these findings, to assess the influence of relevant lesion characteristics, and to determine the impact of treatment of PLMS on hypertension, stroke prevention, and rehabilitation. Characterization of lesion site, etiology, chronology, clinical course, and neurological disability will be important for prospective assessment of the impact of PLMS in future studies. We hope this study will alert clinicians to the associations between PLMS and stroke, as this may have implications for stroke prevention and recovery.
DISCLOSURE STATEMENT
This was not an industry supported study. The authors have indicated no financial conflicts of interest.
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