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This chapter reviews the approaches that have been used to identify genomic variation that may shape circadian entrainment and point new directions of research. It addresses some issues concerning study designs that may increase the efficiency of finding genetic components of the circadian clock in human. If the inter-individual differences in human time-of-day preference or in chronotype are extreme, they can manifest themselves as familial syndromes. The application of ethnicity markers is meanwhile a routine strategy in genome-wide association (GWA) studies. The GWA strategy is more reliable than a candidate gene approach. Human entrainment to different photoperiods may involve substantial plasticity in individual circadian period and phase of entrainment. High-throughput analyses are applied in circadian rhythms research. The authors have recently applied high-throughput genomics to identify alleles associated with phase of entrainment in extreme chronotypes.
Written and edited by leading clinicians and researchers in sleep medicine, this is the first book to focus on the causes, consequences and treatment of disorders of excessive sleepiness. Extensive coverage is provided for all known causes of sleepiness, including sleep deprivation, obstructive sleep apnea syndrome, narcolepsy and other hypersomnias of central origin, shift work, and medical and psychiatric disorders. Since many causes of sleepiness are difficult to differentiate from each other, and treatment modalities can vary greatly from one disorder to another, this book helps the clinician to formulate a differential diagnosis that will ultimately lead to the correct diagnosis. Epidemiology, evaluation of the sleepy patient, diagnostic investigations including neuroimaging, subjective and objective testing, cognitive effects of sleepiness, motor vehicle driving issues, medico-legal aspects of sleepiness, and therapy are also discussed in detail. This is an essential resource for neurologists, psychiatrists and sleep specialists.
The evaluation of a patient with excessive sleepiness requires that a detailed sleep history is taken with medical, psychiatric, and psychosocial factors considered, and a differential diagnosis developed. This chapter deals with the important elements in the clinical evaluation of patients with excessive sleepiness. The social history should be elicited, particularly relationships with other family members, and including determination of any financial, personal or social stresses that may contribute to sleep disturbance. Some sleep disorders including sleep apnea syndrome, narcolepsy, recurrent hypersomnia as well as restless legs syndrome, have a familial tendency. The physical examination ideally should be comprehensive and focus on respiratory, cardiovascular, gastrointestinal, endocrine and neurological evaluation. The patient who is sleepy may be asked to complete various tests of performance, such as a psychomotor vigilance test (PVT), or other tests of cognitive ability.
Circulating melatonin is metabolized primarily in the liver, and secondarily in the kidney. Melatonin has been used successfully in the treatment of insomnia and circadian rhythm sleep disorders. Several studies show that melatonin levels are lower in Alzheimer's disease (AD) patients compared to age-matched control subjects. If the expectation of melatonin activity in AD is to be neuroprotective, the treatment must be initiated at the earliest possible stage of the disease. There is substantial evidence that fragmented sleep, advanced sleep phase syndrome, insomnia, and impaired daytime alertness seen in advanced age are the result of brain dysfunction that is closely linked to disruptions in the regulation of circadian rhythms. The aging process is multifactorial, and no single factor seems to be of basic importance. An example of the effect melatonin has on aging is that in AD and mild cognitive impairment (MCI) patients.
Sleep is a complex behavior. It may be altered by many different factors including age, genetics, volitional control, timing, previous time awake, and environment. The state of wakefulness regularly alternates with the states of sleep. Polysomnography recordings are scored for movement time. Active wakefulness is characterized by a continuous electroencephalographic (EEG) theta activity associated with eye movements and muscular artifacts. Infants, children, and adolescents show different stages of maturation of sleep, in terms of polysomnographic patterns, architecture, and duration of sleep. The duration of nocturnal sleep depends on several factors. Voluntary control of the sleep time is among the most significant in human beings. Young adults report sleeping approximately 7.5 hours a night on weekday nights and 8.5 hours on weekend nights. The timing of sleep has obvious repercussions both on the duration and on the architecture of sleep.
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