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Biomedical subjects

L F Fogg

Publications and source records attributed to L F Fogg.

16 recordsLinked to original sources
PubMed1997

Which environmental variables are related to the onset of seasonal affective disorder?

The regular fall-winter onset of seasonal affective disorder is believed to be related to seasonal changes in the environment. However, the high correlation among various environmental variables has made it difficult to distinguish which ones may play a causal role. Photoperiod should explain variations in onset risk across both latitude and day of the year because it varies as a function of only these 2 factors. In Study 1, the authors found this to be the case using data from 5 locations. Environmental factors that vary from year to year should explain variations in onset risk across both time of year and actual year. In Study 2, the authors examined data from 7 years at 1 location and failed to find evidence of this effect for daily hours of sunshine, mean daily temperature, and total daily radiation. Findings support photoperiod as being related to the onset of seasonal affective disorder.

Adult↗
PubMed1997

Conflicting bright light exposure during night shifts impedes circadian adaptation.

This simulated night shift field study compared high-intensity ("bright") light exposures designed to either facilitate or conflict with adaptation to a 9-h phase shift of the sleep/dark schedule. There were 7 days of baseline with night sleep followed by 8 night shifts with day sleep in a 2 x 2 design with factors bright light (facilitating vs. conflicting) and direction of shifted sleep/dark (delayed vs. advanced). A total of 32 subjects (8 in each group) were exposed to 3 h of bright light (about 5,000 lux) and 5 h of ordinary indoor room light of "dim" light (< 500 lux) during each 8-h night shift. The bright light was timed according to the light phase-response curve (PRC) to delay or advance rhythms; it was timed to occur either before or after the baseline body temperature minimum, which served as an estimate of the PRC crossover point between delays and advances. Core body temperature was measured continuously and demasked to determine daily temperature minima. Significantly more subjects showed large temperature rhythm phase shifts (> or = 6 h during the last 4 night shifts relative to baseline) with facilitating bright light compared to conflicting bright light as well as with delayed sleep/dark compared to advanced sleep/dark. The combination of facilitating bright light and delayed sleep/dark produced large phase delay shifts in all subjects tested. By contrast, the combination of conflicting bright light and advanced sleep/dark resulted in very small phase shifts in most subjects. Because bright light timed to delay usually was not able to phase shift rhythms when sleep/dark was advanced, it appears that the timing of sleep/dark was as important as the timing of the bright light. There was a relationship between the amount of phase shift and the individual's baseline phase when sleep/dark was delayed. Larger phase delays were achieved by subjects with later baseline temperature minima and greater eveningness on the Morningness-Eveningness Questionnaire. These results show that it is important to time bright light appropriately to achieve circadian adaptation to the night shift and that individual differences play an important role in the ability of the circadian system to phase shift.

Adaptation, Physiological↗
PubMed1996

Stable trait components of hopelessness: baseline and sensitivity to depression.

Hopelessness (H) plays an important theoretical and practical role in depression. The authors hypothesized that a patient's H is comprised of (a) a baseline level of H when not depressed and (b) an increment in H related to the severity of depression at the time and the person's rate of increase in H as a function of severity of depression (sensitivity). Baseline and sensitivity are explanatory stable traits; H and depression are observed, time-varying states. The corresponding statistical model described well the longitudinal data of 316 participants. Baseline and sensitivity were uncorrelated and correlated with different clinical and demographic variables. Baseline predicted a future suicide attempt; sensitivity and H when depressed did not. It may be useful to ask "How hopeless is this person when not depressed and how much more hopeless is he or she when depressed?", rather than simply "How hopeless is this depressed person?"

Adolescent↗
PubMed1995

Circadian rhythm adaptation to simulated night shift work: effect of nocturnal bright-light duration.

We compared bright-light durations of 6, 3 and 0 hours (i.e. dim light) during simulated night shifts for phase shifting the circadian rectal temperature rhythm to align with a 12-hour shift of the sleep schedule. After 10 baseline days there were 8 consecutive night-work, day-sleep days, with 8-hour sleep (dark) periods. The bright light (about 5,000 lux, around the baseline temperature minimum) was used during all 8 night shifts, and dim light was < 500 lux. This was a field study in which subjects (n = 46) went outside after the night shifts and slept at home. Substantial circadian adaptation (i.e. a large cumulative temperature rhythm phase shift) was produced in many subjects in the bright light groups, but not in the dim light group. Six and 3 hours of bright light were each significantly better than dim light for phase shifting the temperature rhythm, but there was no significant difference between 6 and 3 hours. Thus, durations > 3 hours are probably not necessary in similar shift-work situations. Larger temperature rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better overall mood.

Adolescent↗
PubMed1995

Use of personal characteristics in the selection of astronauts.

Which personal characteristics are used in selecting astronauts? We decided to examine this question using National Aeronautics and Space Administration (NASA) archival data collected on 2288 applicants. Undergraduate grade point average, graduate grade point average, and several facets of aviation experience were the best predictors of who was interviewed and then selected to be an astronaut. Adjustments were made to insure that a sufficient number of women and minority group members were selected, while still maintaining high selection standards. The selection process seems well-designed, and follows explicit NASA guidelines. We suggest simplifying the selection process by using a single discriminant function as an interview and/or selection criterion.

Astronauts↗
PubMed1994

Dark goggles and bright light improve circadian rhythm adaptation to night-shift work.

We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.

Adaptation, Physiological↗
PubMed1994

Interactions of risk factors in predicting suicide.

The authors examined interactions among risk factors for suicide, a strategy not typically followed in suicide research. Their results suggest an explanation for gender differences in suicide rates and qualifications in the relationship between hopelessness and suicide based on history of drug and alcohol abuse.

Adolescent↗
PubMed1994

Predicting astronaut effectiveness: a multivariate approach.

In this study, measures of astronaut effectiveness were administered to volunteers from the astronaut corps in order to validate psychological "select-in" criteria for long-duration space missions. Using a peer nomination format, astronauts rated their peers with whom they had either flown or trained. Factor analysis revealed two latent performance dimensions: job competence and group living. The job competence dimension measured the instrumental aspects relating to job knowledge and job performance. The group living dimension measured the interpersonal aspects relating to teamwork and desirability as a colleague on Space Station. Analyses revealed that the personality variables could explain a significant proportion of the variance in the group living performance dimension, but not the job competence performance dimension. The findings are not surprising since astronauts are highly screened on the basis of past attainment, but are not as highly screened on aspects relating to teamwork and interpersonal concerns.

Astronauts↗
PubMed1994

Psychological predictors of astronaut effectiveness.

Are the personality characteristics of astronauts related to their professional effectiveness? In order to answer this question, effectiveness and personality data were collected from 65 NASA astronauts. Several findings emerged from these data. Five personality subscales were related to effectiveness in one form or another. They were: high Negative Expressivity and Negative Communion (subordinate and gullible), low Impatience and Irritability, low Openness (to new ideas and experiences), low Negative Instrumentality (egoism) and high Agreeableness. Examining the graphs of these relationships indicated that they were not linear. This examination indicated that high levels on these undesirable personality characteristics (e.g., Impatience/Irritability) were distributed across all levels of effectiveness. Low levels of the undesirable personality characteristics were found only among the most effective astronauts. We concluded that these other-directed personality qualities will assume increasing importance in long-term spaceflight, and consequently, should be the focus of greater attention in future astronaut selection and training.

Adult↗
PubMed1993

The circadian rhythm of temperature during light treatment for winter depression.

Circadian rhythm abnormalities have been implicated in winter seasonal affective disorder. We examined the circadian temperature rhythm of 22 patients with winter depression and 10 normal controls who had participated in various high-intensity light treatment experiments. We did not find abnormalities in the baseline phase or amplitude of the temperature rhythm in patients compared to controls. Nor did we find abnormalities in the phase-shifting response to morning light. There was some evidence that the "phase-delayed" half of the patients responded poorly to phase advances produced by morning light, whereas the "phase-advanced" half of the patients responded poorly when their rhythms delayed. However, the antidepressant responses during the best week (week of lowest depression score) were unrelated to temperature rhythm phase shifts. In general, there was not strong support for a relationship between circadian rhythms changes and antidepressant response.

Adult↗
PubMed1990

Predicting response to treatment: differentiating active-factor and non-specific effects.

An important step in providing treatment is prediction of which treatments will be effective for which patients. Common methods for prediction of efficacy, however, are inconsistent with the assumptions of the standard placebo-control paradigm for establishment of efficacy. This is because in prediction of the observed response, one ignores the distinction between response attributable to non-specific factors and that attributable to active-treatment factors. This paper presents a paradigm for the use of log-linear analysis that allows for the development of predictive methods that take into account this distinction. An example with simulated data demonstrates how, if this distinction is ignored, one can reach misleading conclusions and make non-optimal treatment decisions as a result of an inaccurate cost-benefit analysis of the treatment.

Evaluation Studies as Topic↗
PubMed1990

Sex differences in the lifetime prevalence of depression: does varying the diagnostic criteria reduce the female/male ratio?

Most studies report the lifetime prevalence of major depressive disorder to be higher among women than men. One possible explanation is that this finding is the result of the diagnostic criteria used, in particular the inclusion of criterion symptoms associated with depressed mood. The number of criterion symptoms required for a diagnosis were varied and applied to 2163 first-degree relatives of affectively disordered probands of the NIMH Collaborative Study of the Psychobiology of Depression. Results indicated that differences between men and women in number of symptoms reported could not account for the difference in rates of depression. Women had a greater number of associated symptoms only at higher symptom levels, suggesting an excess of women only above a diagnostic threshold. Thus, findings supported a true difference in rates of major depressive disorder rather than a general trend for women to remember or report more criterion symptoms.

Adult↗
PubMed1990

Concordance of symptoms in recurrent depressive episodes.

The presence or absence of 12 depressive symptoms was examined in 93 bipolar and 108 unipolar patients who had two discrete episodes of major depression over a 5-year period. For each symptom the concordance of its presence or absence across episodes was low. The agreement observed was largely that to be expected by chance. A substantial amount of concordance was obtained if differences in episode intensity (propensity to have symptoms) were taken into account. This suggests that although there may be factors related to depression which remain stable across episodes, symptom presentation is moderated by other factors, such as intensity, which vary from episode to episode.

Adult↗
PubMedDate not supplied

Definition of a responder: analysis of behavioral, cardiovascular, and endocrine responses to varied workload in air traffic controllers.

Individual differences in behavioral, cardiovascular, and endocrine responses to varying workload among 381 air traffic controllers were assessed using random regression modeling. Although most men showed significant increases in behavioral arousal associated with increasing planes, there were major individual differences in response in systolic and diastolic blood pressure, heart rate, and cortisol. Approximately 20% to 25% of those studied had large increases in each of these domains, along with a smaller group showing inverse responses in heart rate and cortisol. There was also evidence of a smaller number of enhanced responders within the highest groups, who tended to have more missing values at higher levels of workload. There was convergence in the definition of responders using three statistical strategies: random regression, correlational analyses, and ANOVA. Response in one physiological/behavioral domain was essentially independent of response in another, supporting the conclusion of specificity, rather than a global tendency to respond to increasing work load.

Adult↗
PubMedDate not supplied

Blood pressure reactivity in the evaluation of resting blood pressure and mood responses to pindolol and propranolol in hypertensive patients.

OBJECTIVE: The purpose of this exploratory study was to evaluate the relationship of blood pressure reactivity during exercise to treatment responsiveness to two commonly used beta-adrenergic blocking agents, propranolol and pindolol. DESIGN: Prospective, placebo-controlled, balanced, cross-over clinical trial. SETTING: University-affiliated medical center. PATIENTS: A convenience sample of 19 white male subjects with mild to moderate essential hypertension were studied. The mean age was 63.4 years (SD = 5.2). The mean resting systolic blood pressure (SBP) was 158.6 mm Hg (SD = 12.3) and mean resting diastolic blood pressure (DBP) was 96.4 mm Hg (SD = 8.6). They had no clinical evidence of secondary hypertension, diabetes, heart, liver, pulmonary, or renal disease. OUTCOME MEASURES: Resting blood pressure; blood pressure reactivity to exercise; self-report measures of depressive symptoms, and mood disturbances. INTERVENTION: Antihypertensive medication was tapered off and subjects were free of all prescription drugs for 2 weeks. Subjects were randomly assigned to propranolol-pindolol or pindolol-propranolol group. Each 4- to 6-week treatment phase was preceded by a 2-week placebo phase. At the end of the initial placebo phase and each active drug treatment phase, subjects were assessed for depression and mood disturbances by use of standardized measures and were given a graded exercise test on a cycle ergometer. Resting blood pressure was assessed weekly and before each exercise test. RESULTS: Significant relationships between DBP reactivity to exercise during the placebo phase and the degree of blood pressure and mood responsiveness to pindolol and propranolol treatment were observed. Subjects demonstrating high DBP reactivity required high doses of beta-blocker for resting DBP reduction, and these subjects showed the least change in mood at high doses. Similar patterns were found for the relationship of SBP reactivity and blood pressure and mood responsiveness to drug treatment, but these relationships were not statistically significant. CONCLUSIONS: DBP reactivity to exercise during the placebo phase provides unique information about the essential hypertensive patient. DBP reactivity and drug dose were important determinants of resting blood pressure and mood responsiveness to both pindolol and propranolol. DBP reactivity and perhaps SBP reactivity may be useful measures in the study of central adrenergic and peripheral cardiovascular pathophysiology.

Affect↗