br Results The mean age for the ND
Results The mean age for the ND group was 72±5.32, and 78.5±5.61 for the D group; there was no statistical difference between them (p=0.696). The underlying disease, for which the patients were admitted to the hospital did not influence the difference in the results since admission diagnoses were counterbalanced (Table 1). In ND patients (n=6), saliva melatonin exhibited low levels in the day and high levels in the night, resulting in a daily rhythm in melatonin concentration (see Fig. 1A). The ANOVA indicated statistical differences between light and dark phases (F (1,10)=174.48; p<0.0001). In the delirium group, melatonin levels remained low in the morning and in the evening, thus resulting in no daily rhythm. Analyzing the seven days (the day of onset of delirium, three days before and three days after), the ANOVA did not show statistical differences between the day and night values (F(1,12)=1.051; p=N.S; see Fig. 1A). In patients that developed delirium, melatonin levels turned out constant three days before the diagnosis of delirium was given, while melatonin levels in the ND remained rhythmic even three days prior to discharge. The ANOVA indicated significant differences between groups (F(1,66)=48.90; p<0.00001), due to the factor time (F(5,66)=8.977; p<0.0001), and in the interaction of groups X time (F (5,66)=17.447; p<0.00001) (see Fig. 1B). Finally, we observed that melatonin levels in the group of patients with delirium, show a loss of rhythmicity after and before of delirium (Fig. 1C).
Discussion Delirium is a common syndrome that increases morbidity and mortality in the hospitalized population, which can be a frightening and distressing experience for patients, their azilsartan medoxomil and caregivers . The need for early diagnosis is crucial to improve the prognosis of the sufferer. This study suggests that there is a relationship between the syndrome of delirium and melatonin daily rhythms. This relationship was previously demonstrated in a group of patients who developed delirium syndrome after alcohol withdrawal . The incidence of delirium is also related to the photoperiod, with a higher incidence of delirium in winter when days are short and melatonin production is increased . This relationship was also previously reported by Wahlund et al. , who found that melatonin levels were associated with the level of psychomotor activity in subtypes of affective disorders. The sleep-wake cycle and psychomotor activity are both under significant circadian regulation and appear to be disturbed in patients developing delirium, suggesting that the integrity of the circadian system is affected preceding or during the onset of delirium . Moreover there is evidence that exogenous melatonin at low doses administered every night to elderly patients admitted to intensive care may be a potential protective agent against the development of delirium . However, once an initial episode of delirium is registered, melatonin does not reduce the severity of delirium, duration of hospital stay, the restraint or sedative use, or mortality [18,19], which further supports the preventive role of melatonin administration in the environment clinic  and in the surgical setting . Delirium is a syndrome that requires an early diagnosis to improve patients\' prognosis . This study suggests a possible relationship between delirium and loss of melatonin rhythmicity. The limitations of our study are the reduced sample size, and lack of control for other variables besides age.
Conflict of interest
Introduction In recent years, sleep disturbances have been extensively reported in the literature, affecting all age groups. Numerous studies have reported a high prevalence of sleep problems in the general population with rates varying between 10–48% [1–4]. In Brazil, studies carried out in São Paulo city identified a prevalence of objective insomnia of 32% . Moreover, a marked increase in sleep-related complaints was found, such as difficulties initiating and maintaining sleep .