Pain and sleep disturbances with special reference to fibromyalgia and rheumatoid arthritis.

Pain has been reported to be a leading cause of insomnia essential parameters, thereby interacting with the course of the disease [3]. On the other hand, sleep disturbances in medical illness, where >70% of the patients complain of sleep problems [1, 2]. Most studies of pain and sleep, may decrease the pain threshold [10]. Pain and sleep relationships probably reflect the various pathogenetic however, have focused on rheumatic diseases where the prevalence of sleep disturbances has been reported to factors underlying the different diseases. Thus, in patients with FM, the pain is most likely multifactorial be very high [3], and many of the daytime symptoms in these patients, such as pain, stiffness and fatigue, may and assumed primarily to involve a central pain modulation disorder [11], whereas the pain in RA, however, is have a close link to the non-restorative sleep pattern associated with the disease [4]. Knowledge of the abnorprobably caused mainly by peripheral nociceptive inputs in joint afferents which show enhanced responsiveness malities in the sleep process may, therefore, improve our understanding of the disease and lead to a better due to the inflammation [12]. Correspondingly, the interaction between sleep and pain probably differs with treatment of the patients. Especially in fibromyalgia (FM ) and rheumatoid arthrespect to sensory, physiological and behavioural aspects in the two diseases. ritis (RA), reports based on objective studies have documented pathological findings during sleep. Pain Sleep difficulties, as well as related daytime symptoms such as fatigue and morning stiffness, have been reported provoked by injury or disease is the net effect of peripheral nociceptive activation and different biochemical, in >75% of patients with FM, and the prevalence of awakenings and non-restorative sleep is greater than physiological and psychological mechanisms that involve most parts of the central nervous system. reported in RA [3]. In several studies, the musculoskeletal symptoms and number of tender points were Therefore, pain in these diseases may probably influence the sleep process. strongly associated with the non-restorative sleep pattern [13]. An altered chronobiological distribution in sympThe physiological functions of sleep are partly unknown. Humans alternate in a cycle of sleep and toms was reported in patients with FM [4] and, correspondingly, a change in the normal diurnal rhythm of wakefulness called the circadian rhythm. This cyclicity is also seen in other physiological variables, such as cortisol has also been reported [14]. Serotonin metabolism in the central nervous system seems to play a role many hormones (e.g. growth hormone, prolactin, melatonin), urine secretion, blood pressure, body temperain the regulation of NREM sleep, pain and affective states [15], and a possible link between sleep disturbture, etc. [5, 6 ]. The sleep process itself is also characterized by cyclicity, and the electroencephalogram (EEG), ances and low levels of brain serotonin has been suggested. Therefore, tryptophan, which is a serotonin indirectly reflecting the neuronal activity in the brain, is of major importance in the description of the sleep. precursor, may be important for the symptoms, and lower concentrations of tryptophan and metabolites Traditionally, sleep is divided into non-rapid-eyemovement (NREM) stages 1–4 with increasing depth have been found in the cerebrospinal fluid of patients with FM [16 ]. and rapid-eye-movement (REM ) sleep. The belief that sleep is a static condition has been replaced by the The sleep disturbances in FM have also been related to growth hormone secretion and lower levels of assumption that this state is a dynamic form of rest that conserves energy and permits reorganization of cortical growth hormone-related peptide have been found in these patients. As most growth hormone is proneuronal activity, among other functions [7]. The deepest sleep stages especially seem to reflect homeostatic duced pulsatively mainly during slow-wave sleep (SWS=NREM3+4), disturbances of this sleep stage processes for the body and the mind, although this theory cannot explain all aspects of mammalian sleep may result in decreased secretion of growth hormone. Although fragmented sleep and other sleep disturbances [8]. In accordance with sleep as a restorative process, anabolic hormones are released mainly during sleep and may theoretically disturb nocturnal hormone secretion, the role of neurotransmitter balance and neuroendocrine evidence exists that a boosting of the immune system occurs during the night [9]. Thus, there seems to be a axis aberrations in FM is still unclear and the subject awaits further studies. relationship between dynamic changes in sleep and variously cellular, hormonal and immunological Different studies regarding sleep architecture in FM have been conducted since the first report by Moldofsky functions. Pain may influence the sleep process and alter these et al. [10]. Various criteria have been proposed for FM