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Biomedical subjects

M W Johns

Publications and source records attributed to M W Johns.

At least 19 recordsLinked to original sources
PubMed2000

Sensitivity and specificity of the multiple sleep latency test (MSLT), the maintenance of wakefulness test and the epworth sleepiness scale: failure of the MSLT as a gold standard.

Excessive daytime sleepiness (EDS) is an important symptom that needs to be quantified, but there is confusion over the best way to do this. Three of the most commonly used tests: the multiple sleep latency test (MSLT), the maintenance of wakefulness test (MWT) and the Epworth sleepiness scale (ESS) give results that are significantly correlated in a statistical sense, but are not closely related. The purpose of this investigation was to help clarify this problem. Previously published data from several investigations were used to calculate the reference range of normal values for each test, defined by the mean+/-2 SD or by the 2.5 and 97.5 percentiles. The 'rule of thumb' that many people rely on to interpret MSLT results is shown here to be misleading. Previously published results from each test were also available for narcoleptic patients who were drug-free at the time and who by definition had EDS. This enabled the sensitivity and specificity of the three tests to be compared for the first time, in their ability to distinguish the EDS of narcolepsy from the daytime sleepiness of normal subjects. The receiver operator characteristic curves clearly showed that the ESS is the most discriminating test, the MWT is next best and the MSLT the least discriminating test of daytime sleepiness. The MSLT can no longer be considered the gold standard for such tests.

Adolescent↗
PubMed1994

Sleepiness in different situations measured by the Epworth Sleepiness Scale.

This investigation examines how the sleep propensity (SP) in one test situation, such as the Multiple Sleep Latency Test (MSLT), is related to sleepiness in daily life, as assessed by the Epworth Sleepiness Scale (ESS). This is a self-administered questionnaire, the item scores from which provide a new method for measuring SPs in eight different real-life situations. The ESS item scores were analyzed separately in four groups of subjects: 150 adult patients with a variety of sleep disorders, 87 medical students who answered the ESS on two occasions 5 months apart, 44 patients who also had MSLTs and 50 patients whose spouses also answered the ESS about their partner's sleepiness. The ESS item scores were shown to be reliable (mean rho = 0.56, p < 0.001). The SP measured by the MSLT was related to three of the eight item scores in a multiple regression (r = 0.64, p < 0.001). The results of nonparametric ANOVA, Spearman correlations, Wilcoxon's t tests, item and factor analysis suggest that individual measurements of SP involve three components of variation in addition to short-term changes over periods of hours or days: a general characteristic of the subject (his average SP), a general characteristic of the situation in which SP is measured (its soporific nature) and a third component that is specific for both subject and situation. The SP in one test situation, including the MSLT, may not be a reliable indicator of a subject's average SP in daily life. Perhaps we should reexamine the current concept of daytime sleepiness and its measurement.

Adult↗
PubMed1993

Daytime sleepiness, snoring, and obstructive sleep apnea. The Epworth Sleepiness Scale.

The Epworth Sleepiness Scale (ESS) is a simple questionnaire measuring the general level of daytime sleepiness, called here the average sleep propensity. This is a measure of the probability of falling asleep in a variety of situations. The conceptual basis of the ESS involves a four-process model of sleep and wakefulness. The sleep propensity at any particular time is a function of the ratio of the total sleep drive to the total wake drive with which it competes. ESS scores significantly distinguished patients with primary snoring from those with obstructive sleep apnea syndrome (OSAS), and ESS scores increased with the severity of OSAS. Multiple regression analysis showed that ESS scores were more closely related to the frequency of apneas than to the degree of hypoxemia in OSAS. ESS scores give a useful measure of average sleep propensity, comparable to the results of all-day tests such as the multiple sleep latency test.

Adolescent↗
PubMed1992

Reliability and factor analysis of the Epworth Sleepiness Scale.

The Epworth Sleepiness Scale (ESS) is a self-administered eight-item questionnaire that has been proposed as a simple method for measuring daytime sleepiness in adults. This investigation was concerned with the reliability and internal consistency of the ESS. When 87 healthy medical students were tested and retested 5 months later, their paired ESS scores did not change significantly and were highly correlated (r = 0.82). By contrast, ESS scores that were initially high in 54 patients suffering from obstructive sleep apnea syndrome returned to more normal levels, as expected, after 3-9 months' treatment with nasal continuous positive airway pressure. The questionnaire had a high level of internal consistency as measured by Cronbach's alpha (0.88). Factor analysis of item scores showed that the ESS had only one factor for 104 medical students and for 150 patients with various sleep disorders. The ESS is a simple and reliable method for measuring persistent daytime sleepiness in adults.

Adolescent↗
PubMed1991

Polysomnography at a sleep disorders unit in Melbourne.

OBJECTIVE: To outline the procedure of polysomnography as carried out in a sleep disorders unit in Melbourne and to describe the patients undergoing polysomnography in terms of their age and sex and the sleep disorder diagnosed. DESIGN: A retrospective survey of consecutive patients who required diagnostic polysomnography. SETTING: The Sleep Disorders Unit at Epworth Hospital, a large private hospital in Melbourne. PATIENTS: Two hundred consecutive patients who underwent polysomnography over a seven-month period. Their ages ranged from 19 to 77 years. INTERVENTIONS: All patients had diagnostic polysomnography for one night in the sleep laboratory. This involved 12 to 14 physiological variables being monitored continuously overnight by means of a new digital recording and sleep analysis system. MAIN OUTCOME MEASURES: Patients were categorised according to their main sleep disorder or primary diagnosis. Additional sleep disorders in some patients were categorised as secondary diagnoses. RESULTS: The commonest age group among both male and female patients was 40-49 years. Overall, men outnumbered women three to one. Almost two-thirds of all patients had as their primary diagnosis some degree of obstructive sleep apnoea syndrome or simple snoring. The next most common diagnosis was periodic limb movement disorder. The remaining diagnoses included a variety of sleep disorders, from narcolepsy to sleep terrors. CONCLUSIONS: Despite its complexity and time-consuming nature, polysomnography is an essential procedure for the diagnosis and treatment of a wide range of sleep disorders. More sleep laboratories and a greater emphasis on the multidisciplinary teaching of sleep disorders medicine will be required in Australia.

Adult↗
PubMed1991

A new method for measuring daytime sleepiness: the Epworth sleepiness scale.

The development and use of a new scale, the Epworth sleepiness scale (ESS), is described. This is a simple, self-administered questionnaire which is shown to provide a measurement of the subject's general level of daytime sleepiness. One hundred and eighty adults answered the ESS, including 30 normal men and women as controls and 150 patients with a range of sleep disorders. They rated the chances that they would doze off or fall asleep when in eight different situations commonly encountered in daily life. Total ESS scores significantly distinguished normal subjects from patients in various diagnostic groups including obstructive sleep apnea syndrome, narcolepsy and idiopathic hypersomnia. ESS scores were significantly correlated with sleep latency measured during the multiple sleep latency test and during overnight polysomnography. In patients with obstructive sleep apnea syndrome ESS scores were significantly correlated with the respiratory disturbance index and the minimum SaO2 recorded overnight. ESS scores of patients who simply snored did not differ from controls.

Adult↗
PubMed1981

The St. Mary's Hospital sleep questionnaire: a study of reliability.

A systematic sleep questionnaire has been devised for assessing the previous night's sleep of a subject. It has been designed for repeated use. It is completed by the subject and is framed with the needs of the hospital patient in mind. In the present study it was given to 93 subjects in four different groups: 16 surgical inpatients, 21 medical inpatients, 32 psychiatric inpatients (in a general hospital unit), and 24 normal volunteers. Test retest reliability correlations have been derived using a nonparametric correlation coefficient (Kendall's tau). Each of the items achieved statistically significant reliability (p less than 0.0001) in all four groups, with the value for tau on the total sample varying from 0.70 to 0.96. The St. Mary's (or SMH) Sleep Questionnaire is put forward as an instrument that is a systematic inquiry into the subject's experience of sleep and that is composed of items of demonstrable reliability.

Adolescent↗
PubMed1977

Self-poisoning with barbiturates in England and Wales during 1959-74.

Hospital admissions due to acute barbiturate poisoning per million population in England and Wales have decreased since 1965 at about the same rate as NHS prescriptions for barbiturates. Admissions due to poisoning with other drugs have increased, but, largely because the benzodiazepine hypnotics and tranquillisers are much less toxic than the barbiturates that they are replacing, deaths from poisoning with all solids and liquids have decreased. The risk of death from self-poisoning associated with each barbiturate prescription has increased two and a half times since 1961, perhaps partly because greater quantities of barbiturate are being dispensed with each prescription and partly because patients for whom these drugs are still being prescribed would, in the event of an overdose, be unlikely to be found and admitted to hospital in time owing to their age and social circumstances. There is now little to justify prescribing barbiturate hypnotics or sedatives for anyone.

Barbiturates↗
PubMed1976

A warning device which indicates the stoppage of paper in an ink-writing recorder.

A simple and inexpensive warning device is described which indicates when the paper has stopped moving beneath the pens of an inkwriting polygraph. The device operates on the principle that the electrical resistance of the paper under the recorder pen is markedly reduced when the paper stops moving and is made wetter by the ink. A buzzer sounds within a few seconds of the paper stopping and so reduces the possibility of failing to record otherwise irretrievable information, for example during all-night recordings of the EEG in sleep research.

Electronics, Medical↗
PubMed1976

The sleep habits, personality and academic performance of medical students.

The academic performance of 104 fourth-year medical students was assessed in relation to their sleep habits reported in a questionary and their scores on the Minnesota Multiphasic Personality Inventory. Poorer academic performance was related significantly to later times of waking up in the morning, particularly at weekends, and to subjectively poorer quality sleep, but not to the amount of sleep usually obtained. Poor academic performance was related also to scores on scales 3 (hysteria), 4 (psychopathic deviate) and 8 (schizophrenia) of the MMPI. Simple enquiries about sleep habits may make it easier for students who are at greatest risk of academic failure to be identified and helped.

Australia↗
PubMed1976

Factor analysis of analogue scales measuring subjective feelings before and after sleep.

A series of 18 visual analogue scales was used to report the subjective feelings of 38 healthy subjects on 732 occasions during experiments concerned with the quality of sleep. Factor analysis of scores from these scales, both for all subjects combined and within each of four subjects separately, yielded two factors consistently -- 'alertness' and 'tranquillity'. Scores derived from the first factor indicated that, in the laboratory setting levels of immediately after waking in the morning were reduced, in relation to those before falling asleep on the previous night.

Adolescent↗
PubMed1976

A transportable sleep recording system.

A system for monitoring sleep, which can be used in th ward without unduly disturbing either the patient or the medical and nursing staff, is described. The system records the electroencephalogram, electro-oculogram, the basal skin resistance and the galvanic skin resistance. In addition, the delta waves of the EEG are automatically counted and a histogram of their frequency plotted. The system allows a whole night's sleep recording to be compressed into just over a metre of paper.

Adult↗
PubMed1975

Factor analysis of subjectively reported sleep habits, and the nature of insomnia.

Factor analysis was performed on variables used to describe subjectively the sleep habits of three groups of subjects--male patients, female patients, and medical students. Similarities in the six factors from each analysis indicate the existence of dimensions of variation which are common to normal sleep habits and insomnia.

Adolescent↗
PubMed1975

Factor analysis of objective and subjective characteristics of a night's sleep.

Factor analysis was performed on objectively measured and subjectively reported characteristics of 46 nights' sleep in four healthy male subjects. The fragmentation of sleep by awakenings during the night, the delay before falling asleep, the total duration of sleep, and the amount of delta-wave sleep formed the bases of four separate factors.

Adult↗