**3.7 Age**

Sleep difficulties are closely correlated with older age in patients with chronic uremia (Iliescu et al., 2003). Yoshioka et al.(1993) found that advanced age and long-term dialysis therapy directly affected patients experiencing sleep problems. The disorders are similar to those described in the general population, where the prevalence and severity of sleep disorders are also associated with old age. Each decade of age increases the risk of insomnia by 239%, and the risk of overt clinical insomnia by 51% (De Santo et al., 2005). Mollaoğlu (2004) reported a negative correlation between age and sleep quality, with sleep quality decreasing with advanced age in their study of 105 HD patients. In addition, communitybased studies have shown that sleep quality could be deteriorated in elderly patients due to increased frequency of physical diseases, multiple drug use, primary sleep disturbances, or lifestyle modifications (Brandenberger et al., 2003; Kamel & Gammack 2006).

### **3.8 Depression**

The psychiatric condition most commonly causing sleep disorders is depression that may affect up to 50% of this patient population (Covic et al., 2006). The relationship between depression and sleep disorders is well known both in the general population and in patients undergoing hemodialysis (İliescu et al.,2003). Depression can be a cause, as well as a result, of insomnia. Dialysis patients with a Pittsburg Quality Index Sleep score of >5 (patients with a "difficult sleep") have a prevalence of overt depression of 20%, while among ESRD patients reporting a normal sleep**,** the prevalence of depression is almost nil (İliescu et al.,2003).
