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Biomedical subjects

P Tucker

Publications and source records attributed to P Tucker.

At least 37 records · Page 2Linked to original sources
PubMed2001

Measurement properties of the Shiftwork Survey and Standard Shiftwork Index.

The Shiftwork Survey (SS) was introduced, along with the Standard Shiftwork Index (SSI), to provide a set of standardized self-report measures to be used in shiftwork research. However, beyond the initial assessment, no attempt has been made to examine the measurement properties of these scales in an independent sample of shiftworkers. Our goal, therefore, was to examine the measurement properties of these scales in an industrial sample of primarily male shiftworkers (N = 370). We found that all scales had acceptable reliabilities (alphas). The confirmatory factor analyses revealed that the chronic fatigue, coping, job satisfaction, and sleep scales are the weakest psychometrically, and the anxiety, personality (extraversion, neuroticism), general health, and physical health scales are the strongest psychometrically. Using item response theory analyses, we found that the scales overall are generally adequate measures of their underlying constructs, although many items should be altered or omitted. Our results, however, are limited by reliance on a single sample.

Adult↗
PubMed2000

Predictors of post-traumatic stress symptoms in Oklahoma City: exposure, social support, peri-traumatic responses.

Eighty-five adults seeking mental health assistance six months after the Oklahoma City bombing were assessed to determine which of three groups of variables (exposure, peri-traumatic responses, and social support) predicted development of post-traumatic stress disorder (PTSD) symptoms. Variables most highly associated with subsequent PTSD symptoms included having been injured (among exposure variables), feeling nervous or afraid (peri-traumatic responses), and responding that counseling helped (support variables). Combining primary predictors in the three areas, PTSD symptoms were more likely to occur in those reporting counseling to help and those feeling nervous or afraid at the time of the bombing. Implications of these findings are discussed for behavioral health administrators and clinicians planning service delivery to groups of victims seeking mental health intervention after terrorist attacks and other disasters.

Adult↗
PubMed2000

A comparison of some different methods for purifying core temperature data from humans.

Nine healthy females were studied about the time of the spring equinox while living in student accommodations and aware of the passage of solar time. After 7 control days, during which a conventional lifestyle was lived under a 24h "constant routine," the subjects lived 17 x 27h "days" (9h sleep in the dark and 18h wake using domestic lighting, if required). Throughout the experiment, recordings of wrist activity and rectal (core) temperature were taken. The raw temperature data were assessed for phase and amplitude by cosinor analysis and another method, "crossover times," which does not assume that the data set is sinusoidal. Two different purification methods were used in attempts to remove the masking effects of sleep and activity from the core temperature record and so to measure more closely the endogenous component of this rhythm; these two methods were "purification by categories" and "purification by intercepts." The former method assumes that the endogenous component is a sinusoid, and that the masking effects can be estimated by putting activity into a number of bands or categories. The latter method assumes that a temperature that would correspond to complete inactivity can be estimated from measured temperatures by linear regression of these on activity and extrapolation to a temperature at zero activity. Three indices were calculated to assess the extent to which exogenous effects had been removed from the temperature data by these purification methods. These indices were the daily variation of phase about its median value; the ratio of this variation to the daily deviation of phase about midactivity; and the relationship between amplitude and the square of the deviation of phase from midactivity. In all cases, the index would decrease in size as the contribution of the exogenous component to a data set fell. The purification by categories approach was successful in proportion to the number of activity categories that was used, and as few as four categories produced a data set with significantly less masking than raw data. The method purification by intercepts was less successful unless the raw data had been "corrected" to reflect the direct effects of sleep that were independent of activity (a method to achieve this being produced). Use of this purification method with the corrected data then gave results that showed least exogenous influences. Both this method and the purification by categories method with 16 categories of activity gave evidence that the exogenous component no longer made a significant contribution to the purified data set. The results were not significantly influenced by assessing amplitude and phase of the circadian rhythm from crossover times rather than cosinor analysis. The relative merits of the different methods, as well as of other published methods, are compared briefly; it is concluded that several purification methods, of differing degrees of sophistication and ease of application to raw data, are of value in field studies and other circumstances in which constant routines are not possible or are ethically undesirable. It is also concluded that such methods are often somewhat limited insofar as they are based on pragmatic or biological, rather than mathematical, considerations, and so it is desirable to attempt to develop models based equally on mathematics and biology.

Body Temperature↗
PubMed2000

Fluvoxamine reduces physiologic reactivity to trauma scripts in posttraumatic stress disorder.

This study assessed the effect of open-label fluvoxamine treatment for posttraumatic stress disorder (PTSD), depressive symptoms, and physiologic arousal to trauma cues. Baseline psychometric ratings and physiologic assessments of heart rate and blood pressure responses to individualized, taped trauma scripts were determined for 16 patients with PTSD and 16 mentally healthy age- and gender-matched control subjects exposed to at least 1 serious trauma. Patients with PTSD had greater autonomic reactivity than control subjects at baseline, with physiologic measures correlating with the severity of the PTSD for the combined groups. Discriminant analyses indicated that systolic blood pressure best classified patients with PTSD (75% sensitivity) and control subjects (100% specificity), with a stepwise discriminant analysis showing that combined physiologic variables correctly classified 75% of patients with PTSD and 100% of control subjects. After 10 weeks of fluvoxamine treatment (100-300 mg/day), patients' PTSD, depression, and physiologic reactivity improved significantly. Medicated patients with PTSD could not be distinguished statistically from untreated control subjects in any physiologic measure. This dampening of autonomic reactivity after drug treatment corroborates subjective measures of improvement, validating the reported efficacy of fluvoxamine in this open trial.

Adult↗
PubMed2000

Effects of direction of rotation in continuous and discontinuous 8 hour shift systems.

OBJECTIVES: Previous research has produced conflicting evidence on the relative merits of advancing and delaying shift systems. The current study assessed the effects of the direction of shift rotation within 8 hour systems, upon a range of measures including sleep, on shift alertness, physical health, and psychological wellbeing. METHODS: An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by four groups of industrial shiftworkers on relatively rapidly rotating 8 hour systems (n=611). Two groups worked continuous systems that were either advancing or delaying; the other two groups worked discontinuous systems that were either advancing or delaying. RESULTS: Few effects were found of direction of rotation on chronic measures of health and wellbeing, even when the systems incorporated "quick returns" (a break of only 8 hours when changing from one shift to another). This was despite the use of measures previously shown to be sensitive to the effects of a broad range of features of shift systems. However, advancing continuous systems seemed to be associated with marginally steeper declines in alertness across the shift (F (3,1080)=2.87, p<0.05). They were also associated with shorter sleeps between morning shifts (F (1,404)=4.01, p<0.05), but longer sleeps between afternoons (F (1,424)=4.16, p<0.05). CONCLUSIONS: The absence of negative effects of advancing shifts upon the chronic outcome measures accorded with previous evidence that advancing shifts may not be as harmful as early research indicated. However, this interpretation is tempered by the possibility that difficult shift systems self select those workers most able to cope with their deleterious effects. The presence of quick returns in advancing continuous systems seemed to impact upon some of the acute measures such as duration of sleep, although the associated effects on alertness seemed to be marginal.

Adult↗
PubMed2000

Measurement and definition for smoking cessation intervention research: the smoke-free families experience. Smoke-Free Families Common Evaluation Measures for Pregnancy and Smoking Cessation Projects Working Group.

The measures, definitions, and processes used in the Smoke-Free Families clinical trials to assure consistent measurement and reporting of various aspects of the trials are described. Definitions of current smokers at different points in the pregnancy, levels of addiction, biological verification, cessation, stages of change, and intervention approaches are presented along with the rationale underlying their adoption and development.

Family↗
PubMed2000

The changing incidence and spectrum of thyroid carcinoma in Tasmania (1978-1998) during a transition from iodine sufficiency to iodine deficiency.

Exposure to ionizing radiation, changing levels of iodine nutrition, and increased pathologic diagnosis of clinically unimportant thyroid neoplasia have all been proposed as explanations for a worldwide rise in the incidence of thyroid carcinoma (TC) over the past 6 decades. Tasmania is geographically an area of endemic iodine deficiency. In this report, we describe the spectrum of TC in a population averaging 450,000 persons during a 21-yr period that spans the communities transition from iodine sufficiency to iodine deficiency after discontinuation of universal iodine prophylaxis in the mid 1980s. The Tasmanian Cancer Register was used to ascertain all cases of TC diagnosed in Tasmania between 1978 and 1998. Histopathological and demographic data were reviewed. A total of 289 cases of TC were identified. Papillary TC (PTC), follicular TC, medullary TC, and other species accounted for 62%, 23%, 4%, and 11% of cases, respectively. The age standardized incidence rate for total TC increased from 2.45 to 5.33 per 100,000 for females and 0.75 to 1.76 per 100,000 for males between 1978 and 1984 and 1992 and 1998, respectively. A rise in the incidence of PTC by 4.5-fold (P < 0.05) in females and 2.1-fold in males (not significant) was the dominant change over this period. In parallel, the proportion of follicular TC relative to PTC fell from 0.35 to 0.17 during these years (P < 0.05). The rise in PTC incidence was, in part, due to an increase in the occurrence of tumors 1cm or less in diameter. Nonetheless, a 3-fold rise in incidence of larger lesions was also observed during the study period. Forty-three (24%) PTC cases had multifocal disease, 17 (40%) of whom had bilateral tumors. Familial (autosomal dominant) PTC was identified in nine (5%) total PTC cases. Prior studies have linked iodine prophylaxis to a rise in the proportion of differentiated TC, particularly PTC. Our data suggest a complex relationship between iodine nutrition and thyroid tumorigenesis. Factors such as a long latency between changes in iodine nutrition and thyroid tumorigenesis, a dose threshold for the effect of iodine nutrition on thyroid tumorigenesis, and an interaction between iodine nutrition and thyroidal sensitivity to ionizing radiation may all play a role.

Adenocarcinoma, Follicular↗
PubMed2000

Diurnal variations in the mood and performance of highly practised young women living under strictly controlled conditions.

The diurnal variation in a range of psychological functions and core body temperature were investigated in a series of studies involving a total of 24 highly practised young women who lived in a controlled environment and on a strictly regimented 24-hour routine for 6 or 7 days. Ten participants were exposed to the natural light/dark cycle (L/Dc) through windows, whereas the 14 remaining participants saw no daylight, but all had access to normal clock time. A battery of mood and performance tests was completed every 2 hours whilst awake (08:00-00:00), resulting in nine equally spaced measures per waking day. Average time of day (ToD) functions were calculated from the last 5 or 6 days spent in the controlled environment. Significant ToD effects were found for many of the variables taken although the nature of these effects differed across measures, with a 'post-lunch dip' being observed at 16:00 in some variables. Analysis of the standardized data established that all variables presented reliably different ToD functions to core body temperature, whilst factor analyses indicated possible relationships between the variables. It was concluded that those variables that exhibited diurnal variation showed trends that did not parallel those in core body temperature.

Adult↗
PubMed2000

Understanding and treating PTSD: past, present, and future.

After highlighting historical perspectives of posttraumatic stress symptoms, the authors describe PTSD's diagnostic features, frequent co-occurring symptoms and psychiatric disorders, and risk factors for developing this often chronic and disabling illness. In addition, they summarize research findings on the neurobiology of PTSD, including changes in neurotransmitters, hyperactivity of the hypothalamic-pituitary-adrenal axis, autonomic reactivity, and differences in brain structure and function. Finally, they present psychopharmacological and psychotherapeutic treatments, concluding that current clinical practice favors a combination of these two types of treatment, tailored to the patient's needs.

Combined Modality Therapy↗
PubMed1999

Nefazodone in post-traumatic stress disorder: results from six open-label trials.

Nefazodone, an antidepressant which blocks serotonin (5-HT)2 receptors and 5-HT reuptake, was evaluated in the treatment of post-traumatic stress disorder (PTSD) in six open-label studies involving both civilians and combat veterans. Our objective was to report this available pooled data to characterize the response of this drug in PTSD. Specifically, we looked at response rates using three different criteria, the effect of nefazodone on each PTSD cluster and individual symptoms and, lastly, variables that might predict response. One hundred and five outpatients with chronic PTSD were treated with nefazodone titrated up to 600 mg/day, 92 of whom were entered in an intent to treat analysis. We used the percentage drop in score between baseline and endpoint on main scale as a common measure to evaluate outcome. The response criterion of a drop in score of at least 30%, 40% and 50% revealed response rates of 46, 36 and 26%, respectively. Nefazodone showed a broad spectrum of action on PTSD symptoms. This profile might make nefazodone a useful drug to treat PTSD. Predictors of response include age, sex and trauma type. Double-blind, placebo-controlled clinical trials in PTSD are in progress to assess the utility of nefazodone as a treatment in this disorder.

Adult↗
PubMed1999

Distribution of rest days in 12 hour shift systems: impacts on health, wellbeing, and on shift alertness.

OBJECTIVES: To investigate of the effects of distribution of rest days in 12 hour shift systems. Although several studies have examined the effects of compressing work schedules by comparing 8 and 12 hour shift systems, there is little published research examining the various forms of 12 hour shift system. METHODS: An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by a large sample of industrial shiftworkers. The respondents worked 12 hour shift systems that either did or did not incorporate breaks of > 24 hours between the blocks of day and night shifts. For the purposes of the analysis, each of these two groups were further subdivided into those who started their morning shift at 0600 and those who started at 0700. RESULTS: Systems which incorporated rest days between the day and night shifts were associated with slightly higher levels of on shift alertness, slightly lower levels of chronic fatigue, along with longer sleep durations when working night shifts and between rest days. Early changeovers were associated with shorter night sleeps between successive day shifts, but longer and less disturbed day sleeps between night shifts. These effects of changeover time were broadly in agreement with previous research findings. CONCLUSIONS: The distribution of rest days in 12 hour shift systems had only limited effects on the outcome measures, although the few modest differences that were found favoured systems which incorporated rest days between the day and night shifts. It is conceded that the design of the study may have obscured some subtle differences between the shift systems. Nevertheless, it is concluded that the impact of distribution of rest days seems to be minor relative to previously found effects of other features of shift systems--for example, shift duration.

Adult↗
PubMed1999

Beyond the three-process model of alertness: estimating phase, time on shift, and successive night effects.

This paper starts by summarizing the development and refinement of the additive three-process model of alertness first published by Folkard and Akerstedt in 1987. It reviews some of the successes that have been achieved by the model in not only predicting variations in subjective alertness on abnormal sleep-wake schedules but also in accounting for objective measures of sleep latency and duration. Nevertheless, predictions derived from the model concerning alertness on different shifts, and over successive night shifts, are difficult to reconcile with published data on accident risk. In light of this, we have examined two large sets of alertness ratings with a view to further refining the model and identifying additional factors that may influence alertness at any given point in time. Our results indicate that, at least for the range of sleep durations and wake-up times commonly found on rotating shift systems, we may assume the phase of the endogenous circadian component of alertness (process C) to be "set" by the time of waking. Such an assumption considerably enhanced the predictive power of the model and yielded remarkably similar phase estimates to those obtained by maximizing the post-hoc fit of the model. We then examined the manner in which obtained ratings differed from predicted values over a complete 8-day cycle of two, 12-h shift systems. This revealed a pronounced "first night compensation effect" that resulted in shift workers rating themselves as progressively more alert than would be predicted over the course of the first night shift. However, this appeared to be achieved only at the cost of lowered ratings on the second night shift. Finally, we were able to identify a "time on shift" effect whereby, with the exception of the first night shift, alertness ratings decreased over the course of each shift before showing a modest "end effect." We conclude that the identification of these additional components offers the possibility that in the future we may be able to predict trends in accident risk on abnormal sleep-wake schedules.

Animals↗
PubMed1999

Lack of evidence that feedback from lifestyle alters the amplitude of the circadian pacemaker in humans.

Two groups of healthy subjects were studied indoors, first while living normally for 8 days (control section) and then for 18 x 27 h "days" (experimental section). This schedule forces the endogenous (body clock-driven) and exogenous (lifestyle-driven) components of circadian rhythms to run independently. Rectal temperature and wrist movement were measured throughout and used as markers of the amplitude of the circadian rhythm, with the rectal temperature also "purified" by means of the activity record to give information about the endogenous oscillator. Results showed that, during the experimental days, there were changes in the amplitude of the overt temperature rhythm and in the relative amounts of out-of-bed and in-bed activity, both of which indicated an interaction between endogenous and exogenous components of the rhythm. However, the amplitude and the amount of overlap were not significantly different on the control days (when endogenous and exogenous components remained synchronized) and those experimental days when endogenous and exogenous components were only transiently synchronized; also, the amplitudes of purified temperature rhythms did not change significantly during the experimental days in spite of changes in the relationship between the endogenous and exogenous components. Neither result offers support for the view that the exogenous rhythm alters the amplitude of oscillation of the endogenous circadian oscillator in humans.

Activity Cycles↗
PubMed1999

The effect of activity on the waking temperature rhythm in humans.

Nine healthy female subjects were studied when exposed to the natural light-dark cycle, but living for 17 "days" on a 27h day (9h sleep, 18h wake). Since the circadian endogenous oscillator cannot entrain to this imposed period, forced desynchronization between the sleep/activity cycle and the endogenous circadian temperature rhythm took place. This enabled the effects of activity on core temperature to be assessed at different endogenous circadian phases and at different stages of the sleep/activity cycle. Rectal temperature was measured at 6-minute intervals, and the activity of the nondominant wrist was summed at 1-minute intervals. Each waking span was divided into overlapping 3h sections, and each section was submitted to linear regression analysis between the rectal temperatures and the total activity in the previous 30 minutes. From this analysis were obtained the gradient (of the change in rectal temperature produced by a unit change in activity) and the intercept (the rectal temperature predicted when activity was zero). The gradients were subjected to a two-factor analysis of variance (ANOVA) (circadian phase/ time awake). There was no significant effect of time awake, but circadian phase was highly significant statistically. Post hoc tests (Newman-Keuls) indicated that gradients around the temperature peak were significantly less than those around its trough. The intercepts formed a sinusoid that, for the group, showed a mesor (+/-SE) of 36.97 (+/-0.12) and amplitude (95% confidence interval) of 0.22 degrees C (0.12 degrees C, 0.32 degrees C). We conclude that this is a further method for removing masking effects from circadian temperature rhythm data in order to assess its endogenous component, a method that can be used when subjects are able to live normally. We suggest also that the decreased effect of activity on temperature when the endogenous circadian rhythm and activity are at their peak will reduce the possibility of hyperthermia.

Adolescent↗