The renin-angiotensin system, in both its circulating and local tissue roles, is intertwined with multiple other regulatory and signalling mechanisms in various tissues and organ systems. It plays a central role in the normal regulation of arterial blood pressure and in the development of hypertension, which is an immense global public health burden and a crucial modifiable risk factor in the development of cardiovascular diseases. The renin-angiotensin system plays also important roles in a range of other clinical conditions such as heart failure, kidney failure, diabetes mellitus and others. Therapeutic interventions within the renin-angiotensin system include the use of medications such as angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists, which are well established and have been invaluable as clinically effective tools during many years of practical use. Additionally, numerous other therapeutic approaches targeting components of the renin-angiotensin system have been developed or are currently in development. This chapter will discuss details of the roles of this system in the most relevant clinical conditions.

Alexithymia, or the inability to distinguish between bodily feelings and emotions, has been linked to poor sleep quality in some studies. Rare studies examined the associations between electrolyte phosphorus in patients on hemodialysis and their sleep quality, daytime sleepiness, and alexithymia with inflammatory factors. Hemodialysis is a treatment method for terminal renal patients that involves the diffusion of unwanted metabolic products through the dialyzer membrane. Our study aimed to examine whether there was a difference in phosphorus levels, inflammatory factors, and daytime sleepiness according to the hemodialysis patients’ levels of alexithymia. The study involved 170 HD patients that had been treated with chronic dialysis for more than three months. Prior to the hemodialysis procedure, laboratory findings were sampled. Respondents completed the Pittsburgh Sleep Quality Index, the Toronto Alexithymia Scale 26, and the Epworth Sleepiness Scale, and were questioned about depression. The results showed that alexithymic HD patients exhibited significantly higher leukocyte counts, lower predialysis phosphorus values, and more pronounced daily sleepiness than the alexithymia-free group (Mann–Whitney U test, p = 0.02, p = 0.005, and p < 0.001, respectively). We concluded that alexithymia was an independent predictor of high daytime sleepiness in HD patients (OR = 1.05, 95% CI 1.02 to 1.09).

Alexithymia is a construct defined as the inability to differentiate between emotional experiences and bodily sensations. According to existing knowledge, alexithymia may have a major effect on the process of treatment and the outcome of the hemodialysis disease. The objective of this literature review was to determine the significance that alexithymia has for compliance and variables of clinical and mental health in the population of hemodialysis patients. For the above purpose, bibliographic databases “MEDLINE” and “Web of Science” were searched. The matrix method was used in analysis of articles. Searching both databases resulted in 248 articles. After applying exclusion and inclusion criteria, we included results of 13 articles in the literature review. The results of the search are findings regarding the prevalence and correlation of alexithymia with variables of clinical and mental health in hemodialysis patients. Alexithymia is significantly more common in the population of hemodialysis patients, and it has a negative effect on their mental and somatic health. Alexithymia levels in hemodialysis patients are more pronounced in cases where there is a greater number of comorbidities. Alexithymia is the predictor of high mortality rate in the population of hemodialysis patients, independent of other comorbidities.

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