Clinical Investigation
Sleep Disordered Breathing
Frequent Periodic Leg Movement during Sleep Is Associated with Left Ventricular Hypertrophy and Adverse Cardiovascular Outcomes

https://doi.org/10.1016/j.echo.2013.03.018Get rights and content

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.

Section snippets

Patient Population

All patients with indications for polysomnography because of sleep disorders and clinical suspicion of RLS4, 7 as assessed from their medical records (International Classification of Diseases, Ninth Revision, code 333.94) between January 2000 and August 2007 were included in the study. Because clinical diagnosis of RLS requires strict criteria and cannot be assessed from a retrospective review of medical records, the study focused on objective documentation of the severity of periodic leg

Patient Population

Of 584 patients with RLS referred for polysomnography who also had baseline echocardiograms, 274 (47%) had periodic movement index >35/hour. Table 1 summarizes baseline characteristics of the study population. No significant differences were present between the groups in the proportions of patients with prior diagnoses of hypertension, use of antihypertensive medications, diabetes mellitus, hyperlipidemia, prior myocardial infarctions, heart failure, stroke, and abnormal LV ejection fractions

Discussion

The main finding of our study is the recognition that frequent PLMS in patients with RLS referred for overnight polysomnography is an independent risk factor for the presence and severity of LVH and is associated with increased incidence of heart failure and mortality independent of other risk factors for cardiovascular disease.

RLS is one of the most common neurologic conditions,5 which increases with advancing age and is diagnosed clinically on the basis of four essential criteria as outlined

Conclusions

Frequent PLMS in patients with RLS referred for overnight polysomnography identifies those at risk for LVH, and recognizing that periodic movement index >35/hour provides incremental prognostic information to established risk factors makes it a promising risk marker for cardiovascular events in patients with RLS. Because RLS is a common clinical disorder that affects millions of Americans, insights into clinical factors and mechanisms that promote the substrates (such as LVH)22, 23, 24, 25, 26

Acknowledgments

We gratefully acknowledge the editorial assistance of Joe Grundle and Katie Klein and the figure preparation of Brian Miller and Brian Schurrer, all of Aurora Cardiovascular Services.

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    Drs. Jahangir and Mirza's research effort was supported in part by grants R01 HL101240 and R01 HL089542 from the National Heart, Lung, and Blood Institute (Bethesda, MD).

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