Prospective study of restless legs syndrome and mortality among men

Restless legs syndrome in non-dialysis renal patients: is it really that common?

BACKGROUND

Sleep disorders are frequent in chronic kidney disease (CKD). Among them, restless legs syndrome (RLS) may affect up to 60% of patients on dialysis, and it has been related to a poor quality of life and higher cardiovascular risk. Despite its high prevalence in advanced stages of renal disease, RLS frequency in non-dialysis CKD has not been clearly established. The aim of this study was to assess the frequency of RLS in non-dialysis CKD patients (stages 2 to 4) followed in a reference nephrology outpatient clinic.

METHODS

A standardized questionnaire following the international RLS study group diagnostic criteria was self-administered by 110 patients regularly followed in the nephrology clinic. The series comprised 69 men and 41 women, aged 68 ± 13.2 years, with mean serum creatinine of 1.7 ± 0.8 mg/dL. Subsequently, patients classified as probable RLS according to the questionnaire underwent a systematic neurological examination. The presence of peripheral artery disease was evaluated by the ankle-brachial index (ABI).

RESULTS

The frequency of probable RLS according to the questionnaire results was 21% (17% for men and 27% for women). However, after thorough neurological examination, the diagnosis of RLS was confirmed in only 5 patients. Therefore, the overall definitive RLS frequency was 4.5% (within the prevalence reported for the general population) and was higher among women (9.7% vs 0.2%). In the remaining cases symptoms were due to leg discomfort related with other disorders. Patients with probable and improbable RLS were not significantly different in age, ABI, diabetes, and other comorbid circumstances, except for tricyclic antidepressant prescription, which was more frequent in the probable RLS group (17% vs 2%). Renal function was better in definitive RLS patients than cases classified as probable RLS by the questionnaire but not confirmed after neurological exam.

CONCLUSIONS

Although RLS can represent an early manifestation of CKD, its prevalence seems very close to that reported for the general population. Diagnostic confirmation of RLS dramatically falls after expert examination, raising the question whether, in the study of RLS cohorts, CKD has a potentially causal relationship or is a confounding factor associated with other causes of leg discomfort.

Structural brain lesions and restless legs syndrome: a cross-sectional population-based study

OBJECTIVE

To evaluate the association between white matter lesion (WML) volume, silent infarcts and restless legs syndrome (RLS) in a population-based study of elderly individuals.

DESIGN

Cross-sectional study.

SETTING

Population-based Three-City study.

PARTICIPANTS

1035 individuals from the Dijon, France, centre of the Three-City study who had available information on volume of WMLs from MRIs and who answered questions about the prevalence of RLS.

PRIMARY OUTCOME MEASURE

Prevalence of RLS.

RESULTS

WML volume was measured using an automated tissue segmentation method. Logistic regression was used to evaluate adjusted associations between tertiles of WML volume and RLS and between silent infarcts and RLS. 218 individuals (21.1%) were determined to have RLS. Compared with those in the first tertile of WML volume, individuals in the second tertile (OR=1.09; 95% CI 0.75 to 1.60) or third tertile (OR=1.17; 95% CI 0.79 to 1.74) did not have an increased prevalence of RLS. We also did not observe associations between the volume of deep or periventricular WML and RLS; nor did we observe an association between silent brain infarcts and RLS (OR=0.74; 95% CI 0.40 to 1.39). These findings were not modified by age or gender.

CONCLUSIONS

Higher volume of WML and the presence of silent infarcts were not associated with an increased prevalence of RLS in this population-based cohort of elderly individuals.

Association between neurological disorders, functioning, and mortality in the elderly

OBJECTIVES

In aging populations, the prevalence of neurological disorders increases, which imposes high population burden in terms of mortality, disability, and impaired quality of life. The aim of this study was to assess the prevalence of common neurological disorders and signs and their association with functioning and mortality in an elderly general population.

MATERIALS AND METHODS

We used data from the Memory and Morbidity in Augsburg Elderly (MEMO) project, a population-based study of 385 individuals aged ≥65. The prevalence of neurological disorders and signs was assessed by physical examination and medical interview. The basic and instrumental activities of daily living were assessed (ADL, IADL). We assessed the association of neurological disorders and signs with everyday functioning and prospectively analyzed their relationship with mortality.

RESULTS

We observed considerably impaired functioning for cases with stroke, TIA, PD, and mild motor parkinsonian signs (MMPS). All-cause mortality was significantly increased in participants with stroke and MMPS, even after adjusting for co-variables (HR = 2.71 and 1.80, respectively).

CONCLUSIONS

We found that not only specific neurological disorders, but also earlier symptoms are related to impaired functioning and predict mortality in the elderly. These findings have potential clinical relevance for screening and early detection of individuals at risk.

Periodic leg movements during sleep are associated with polymorphisms in BTBD9, TOX3/BC034767, MEIS1, MAP2K5/SKOR1, and PTPRD

STUDY OBJECTIVES

To examine association between periodic leg movements (PLM) and 13 single nucleotide polymorphisms (SNPs) in 6 loci known to increase risk of restless legs syndrome (RLS).

SETTING

Stanford Center for Sleep Sciences and Medicine and Clinical Research Unit of University of Wisconsin Institute for Clinical and Translational Research.

PATIENTS

Adult participants (n = 1,090, mean age = 59.7 years) from the Wisconsin Sleep Cohort (2,394 observations, 2000-2012).

DESIGN AND INTERVENTIONS

A previously validated automatic detector was used to measure PLMI. Thirteen SNPs within BTBD9, TOX3/BC034767, MEIS1 (2 unlinked loci), MAP2K5/SKOR1, and PTPRD were tested. Analyses were performed using a linear model and by PLM category using a 15 PLM/h cutoff. Statistical significance for loci was Bonferroni corrected for 6 loci (P < 8.3 × 10(-3)). RLS symptoms were categorized into four groups: likely, possible, no symptoms, and unknown based on a mailed survey response.

MEASUREMENTS AND RESULTS

Prevalence of PLMI ≥ 15 was 33%. Subjects with PLMs were older, more likely to be male, and had more frequent RLS symptoms, a shorter total sleep time, and higher wake after sleep onset. Strong associations were found at all loci except one. Highest associations for PLMI > 15/h were obtained using a multivariate model including age, sex, sleep disturbances, and the best SNPs for each loci, yielding the following odds ratios (OR) and P values: BTBD9 rs3923809(A) OR = 1.65, P = 1.5×10(-8); TOX3/BC034767 rs3104788(T) OR = 1.35, P = 9.0 × 10(-5); MEIS1 rs12469063(G) OR = 1.38, P = 2.0 × 10(-4); MAP2K5/SKOR1 rs6494696(G) OR = 1.24, P = 1.3×10(-2); and PTPRD(A) rs1975197 OR = 1.31, P = 6.3×10(-3). Linear regression models also revealed significant PLM effects for BTBD9, TOX3/BC034767, and MEIS1. Co-varying for RLS symptoms only modestly reduced the genetic associations.

CONCLUSIONS

Single nucleotide polymorphisms demonstrated to increase risk of RLS are strongly linked to increased PLM as well, although some loci may have more effects on one versus the other phenotype.

Racial differences in the prevalence of restless legs syndrome in a primary care setting

STUDY OBJECTIVE

To assess the prevalence of restless legs syndrome (RLS) in a primary care clinic and in African American (AA) and non-African American (NAA) racial groups.

METHODS

We examined the prevalence of RLS using 1-on-1 interviews in general medicine clinics. Subjects were interviewed using John Hopkins Telephone Diagnostic Interview. All interviews were conducted by trained physicians.

RESULTS

A total of 190 patients were interviewed: 103 AA (58.3% were female) and 87 NAA (59.8% were female). The overall prevalence of definite RLS was 22.6%. The average age was 53 years (standard deviation, 15) in AA and 50 years (standard deviation, 13) in NAA. Among AA, the diagnosis of RLS was definite in 11.65%, probable in 3.88%, negative in 83.5%, and unknown in 0.97%. Among NAA, patients were either identified as definite RLS (35.63%) or not RLS (64.37%); no patients were diagnosed as probable RLS or unknown. Logistic regression analysis was done to determine whether age, race, and sex were statistically significant predictors of an RLS diagnosis. When accounting for the other variables, the association between NAA and RLS prevalence was statistically significant (P = 0.002).

CONCLUSION

Restless legs syndrome is common among primary care clinic patients. Its prevalence in the NAA population is approximately 3 times higher than in the AA group. We found the association between NAA race and RLS prevalence to be statistically significant. Larger studies are needed to further examine the relation between race and RLS prevalence.

Diagnosis, comorbidities, and management of restless legs syndrome

OBJECTIVE

This narrative review describes the differential diagnosis of restless legs syndrome, and provides an overview of the evidence for the associations between RLS and potential comorbidities. Secondary causes of RLS and the characteristics of pediatric RLS are also discussed. Finally, management strategies for RLS are summarized.

METHODS

The review began with a comprehensive PubMed search for 'restless legs syndrome/Willis-Ekbom disease' in combination with the following: anxiety, arthritis, attention-deficit hyperactivity disorder, cardiac, cardiovascular disease, comorbidities, depression, end-stage renal disease, erectile dysfunction, fibromyalgia, insomnia, kidney disease, liver disease, migraine, mood disorder, multiple sclerosis, narcolepsy, neuropathy, obesity, pain, Parkinson's disease, polyneuropathy, pregnancy, psychiatric disorder, sleep disorder, somatoform pain disorder, and uremia. Additional papers were identified by reviewing the reference lists of retrieved publications.

RESULTS AND CONCLUSIONS

Although clinical diagnosis of RLS can be straightforward, diagnostic challenges may arise when patients present with comorbid conditions. Comorbidities of RLS include insomnia, depressive and anxiety disorders, and pain disorders. Differential diagnosis is particularly important, as some of the medications used to treat insomnia and depression may exacerbate RLS symptoms. Appropriate diagnosis and management of RLS symptoms may benefit patient well-being and, in some cases, may lessen comorbid disease burden. Therefore, it is important that physicians are aware of the presence of RLS when treating patients with conditions that commonly co-occur with the disorder.

Restless legs syndrome/Willis-Ekbom disease diagnostic criteria: updated International Restless Legs Syndrome Study Group (IRLSSG) consensus criteria--history, rationale, description, and significance

BACKGROUND

In 2003, following a workshop at the National Institutes of Health, the International Restless Legs Syndrome Study Group (IRLSSG) developed updated diagnostic criteria for restless legs syndrome/Willis-Ekbom disease (RLS/WED). These criteria were integral to major advances in research, notably in epidemiology, biology, and treatment of RLS/WED. However, extensive review of accumulating literature based on the 2003 NIH/IRLSSG criteria led to efforts to improve the diagnostic criteria further.

METHODS

The clinical standards workshop, sponsored by the WED Foundation and IRLSSG in 2008, started a four-year process for updating the diagnostic criteria. That process included a rigorous review of research advances and input from clinical experts across multiple disciplines. After broad consensus was attained, the criteria were formally approved by the IRLSSG executive committee and membership.

RESULTS

Major changes are: (i) addition of a fifth essential criterion, differential diagnosis, to improve specificity by requiring that RLS/WED symptoms not be confused with similar symptoms from other conditions; (ii) addition of a specifier to delineate clinically significant RLS/WED; (iii) addition of course specifiers to classify RLS/WED as chronic-persistent or intermittent; and (iv) merging of the pediatric with the adult diagnostic criteria. Also discussed are supportive features and clinical aspects that are important in the diagnostic evaluation.

CONCLUSIONS

The IRLSSG consensus criteria for RLS/WED represent an international, interdisciplinary, and collaborative effort intended to improve clinical practice and promote further research.

Restless legs syndrome status as a predictor for lower physical function

OBJECTIVE

To examine the potential long-term impact of restless legs syndrome (RLS) and other common sleep complaints on subsequent physical function (PF), we conducted a longitudinal analysis of 12,556 men in the Health Professionals Follow-up Study.

METHODS

We used a set of questions recommended by the International RLS Study Group to assess RLS in 2002. We asked questions regarding other sleep complaints--insomnia, sleep fragmentation, and excessive daytime sleepiness--in 2004. We used the Physical Function (PF-10) survey of the Short Form-36 Health Survey to characterize PF in 1996 and 2008. We examined the 2008 PF-10 scores across categories of baseline RLS (2002), adjusted for age, 1996 PF-10 score, and other potential confounders.

RESULTS

The participants with RLS at baseline had significantly lower PF-10 score 6 years later than those without RLS (mean difference = -2.32, p = 0.01), after adjusting for potential confounders. The magnitude of difference in PF-10 score for RLS symptoms ≥ 15 times/month vs no RLS was more than that of a 5-year increase of age or moderate amount of smoking. Having daily daytime sleepiness and sleep duration ≥ 9 hours/day were associated with lower mean PF value than not having these symptoms (p < 0.05 for both).

CONCLUSIONS

RLS and other sleep complaints are associated with lower PF. Our findings need to be replicated by more longitudinal studies including women and populations of other social and cultural backgrounds. It is important to understand whether RLS is an independent risk factor or a marker for other unknown risk factors for disability.

The relationship among restless legs syndrome (Willis-Ekbom Disease), hypertension, cardiovascular disease, and cerebrovascular disease

Untreated sleep disorders may contribute to secondary causes of uncontrolled hypertension, cardiovascular disease (CVD), and stroke. Restless legs syndrome, or Willis–Ekbom Disease (RLS/WED), is a common sensorimotor disorder with a circadian rhythmicity defined by an uncontrollable urge to move the legs that worsens during periods of inactivity or at rest in the evening, often resulting in sleep disruptions. Sleep disorders such as insomnia and obstructive sleep apnea (OSA) are established risk factors for increased risk of hypertension and vascular diseases. This literature review outlines the lessons learned from studies demonstrating insomnia and OSA as risk factors for hypertension and vascular diseases to support the epidemiologic and physiologic evidence suggesting a similar increase in hypertension and vascular disease risk due to RLS. Understanding the relationships between RLS and hypertension, CVD, and stroke has important implications for reducing the risks associated with these diseases.