NDT Advance Access originally published online on April 12, 2006
Nephrology Dialysis Transplantation 2006 21(6):1732; doi:10.1093/ndt/gfl149
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Reply
Email: solojo77{at}hotmail.comSir,
We thank Dr Di Iorio et al. for their comments and interest in our work. We agree with them about a relevant role of comorbidities as predictors of sleep disorders in dialysed patients, as recently reported by De Santo et al. [1] and Mucsi et al. [2]. In our study [3], we considered only a few clinical conditions associated with uraemia, but our questionnaire included a specific question regarding general medical history that was correctly completed by nephrologists. Taking advantage of Di Iorio et al.'s letter, we decided to evaluate in our sample the role of comorbidities as risk factors for sleep complaints, using the Charlson Comordity Index (CCI). Our dialytic patients with and without sleep disturbances showed a significantly different CCI score (3.13 ± 1.45 vs 2.59 ± 0.99, P < 0.001, respectively). Multivariate logistic regression confirmed that the CCI score was a significant and independent predictor of sleep disorders in dialysed patients (OR for one unit increment in CCI score, 1.44; 95% CI 1.20–1.73; P < 0.001). In patients with end-stage renal disease undergoing dialysis, comorbidities can affect the patients’ outcome per se [4] and increase the risk of sleep disturbances. Thus according to Di Iorio et al., we suggest an attentive assessment of clinical conditions associated with uraemia.
In our study, sleep disorders were related to age, while we did not observe differences regarding the use of any type of drugs, including anti-hypertensive [3]. In the general population, the relationship between hypertension and sleep disorders, particularly insomnia, is known [5]. Recently, De Santo et al. [1] reported a significant independent association between the use of anti-hypertensive drugs and sleep disorders in dialysed patients, but the mean arterial pressure did not differ in subjects with and without sleep complaints. In our opinion, further studies are necessary to evaluate a possible relation between hypertension and disturbances during sleep in uraemic subjects.
The effect of dialysis shift in the morning on insomnia is known [1,3] and, if possible, it should be treated by nephrologists. Even if psychological problems have been suggested to explain symptoms of insomnia on the morning shift, other mechanisms could be implicated (i.e. abnormal circadian rhythms).
Sleep in patients with chronic kidney disease not yet treated with dialysis is disturbed [6], causing insomnia symptoms [7]. In renal failure, several conditions can compromise quality of sleep determining insomnia (i.e. psychological factors, metabolic abnormalities or specific sleep complaints). The largest studies evaluating patients in chronic kidney disease not treated with dialysis did not consider the effect of peculiar disturbances during sleep, such as restless legs syndrome (RLS) or sleep apnoea [6,7]. Only Parker et al. [8] compared sleep variables in patients with chronic kidney disease and those on haemodialysis using polysomnography. They reported a higher respiratory disturbance index and periodic limb-movement index in dialysed patients, but these differences were not significant. Moreover, Parker's sample was too small to consider their results as conclusive. We think that an adequate treatment of sleep complaints in chronic kidney disease and an accurate knowledge of pathophysiology of sleep disturbances associated with renal failure (i.e. RLS and sleep apnoea) depend on the answer to the question: ‘Do sleep disorders differ in dialysed patients and in those with early chronic kidney disease?’. Further studies should investigate this issue.
Conflict of interest statement. None declared.
Sleep Disorder Center Neurology and Clinical Neurophysiology S. Maria della Misericordia Hospital Udine
References
- De Santo RM, Lucidi F, Violani C, Di Iorio BR.Sleep disorders in hemodialized patients: the role of comorbidities. Int J Artif Organs 2005; 28: 557–565[Medline]
- Mucsi I, Molnar AZ, Rethelyi J, Vamos E, Csepanyi G, Tompa G et al. Sleep disorders and illness intrusiveness in patients on chronic dialysis. Nephrol Dial Transplant 2004; 19: 1815–1822
[Abstract/Free Full Text] - Merlino G, Piani A, Dolso P et al. Sleep disorders in patients with end-stage renal disease undergoing dialysis therapy. Nephrol Dial Transplant 2006; 21: 184–190
[Abstract/Free Full Text] - Avram MM. Management of comorbidities in kidney disease in the 21st Century. Kidney Int 2003; 64 [Suppl]: S2–S5
- Janson S, Lindberg E, Gislason T, Elmasry A, Boman G. Insomina in men: a 10-year prospective population based study. Sleep 2001; 15: 425–430
- Iliescu EA, Yeates KE, Holland DC. Quality of sleep in patients with chronic kidney disease. Nephrol Dial Transplant 2004; 19: 95–99
[Abstract/Free Full Text] - De Santo RM, Bartiromo M, Cesare MC, Di Iorio BR. Sleeping disorders in early chronic kidney disease. Semin Nephrol 2006; 26: 64–67[Medline]
- Parker KP, Bliwise DL, Bailey JL, Rye DB. Polysomnographic measures of nocturnal sleep in chronic, intermittent daytime haemodialysis vs those with chronic kidney disease. Nephrol Dial Transplant 2005; 20: 1422–1428
[Abstract/Free Full Text]
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