PubMed Health⌕ Search

Biomedical subjects

D E Bunnell

Publications and source records attributed to D E Bunnell.

17 recordsLinked to original sources
PubMed1990

Napping and sleep disturbances in the elderly.

Elderly patients often describe sleep problems that present diagnostic dilemmas. This study sought to clarify the relationship between patients' reports of daytime napping and nocturnal sleep disturbances by surveying 132 older adults (ages 58-95). Prevalence, frequency, and duration of napping were analyzed with respect to (a) age and sex, and (b) indicators of nocturnal sleep disturbance, including awakenings, latency to sleep onset, and subjective estimates of sleep quality. Age had the greatest effect on napping, with older subjects taking more frequent and longer naps. Although a non-significant trend suggested that the duration of naps may be associated with increased difficulty initiating nocturnal sleep, no significant relationship was observed between any reported napping dimension and indicators of nocturnal sleep difficulty except for a small subgroup who used pharmacologic sleep aids.

Aged↗
PubMed1989

Interactive effects of heat, physical work, and CO exposure on metabolism and cognitive task performance.

The simple and interactive effects of CO exposure and prior physical work on cognitive performance were evaluated in 16 subjects in two hot (WBGT = 30 degrees C) environments. Three levels of carboxyhemoglobin (COHb) (0, 7, 10%) and three workloads (rest, 35%, 60% VO2max) were crossed resulting in nine repeated measures conditions per subject. A bolus + ambient air maintenance technique was used to achieve the targeted COHb levels. Following administration of CO by bolus, subjects either exercised or rested for 50 min, then performed five cognitive tasks: Manikin spatial processing, Sternberg memory, Stroop word-color, visual search, and visual tracking, with and without a secondary mathematics task. The only cognitive impairment associated with an elevated COHb was seen in performance of the second of two sequentially presented Stroop test versions using the same stimuli but with competing instructions. Heat exposure per se had no significant effects on cognitive performance based on comparisons with other subjects who underwent the same protocol in a thermoneutral environment. Elevated COHb was associated with greater reporting of exertion and eye, ear, nose, and throat symptoms during heavy exercise concomitant with greater minute ventilation and heart rate. Except for the latter, these effects were not seen in thermoneutral conditions.

Adult↗
PubMed1988

Passive body heating and sleep: influence of proximity to sleep.

Previous studies have found enhanced delta sleep following body heating. This study assessed the influence of body heating as a function of its proximity to sleep. Electroencephalogram (EEG) sleep patterns were compared following body heating (1 h immersion in water at 41 degrees C) at each of four times of day: morning (MO), afternoon (AF), early evening (EE), and late evening (LE), ending just prior to sleep. A delta filter/integrator system provided objective measures of delta content. Relative to baseline nights, whole-night delta sleep was increased by the two evening heating sessions only, particularly LE heating. Following LE, the increased delta occurred primarily in the first sleep cycle, whereas EE heating elicited increased delta distributed across the later sleep cycles (cycles 2-4). Effects on manually staged indices of slow wave sleep (SWS) were confined to increases in Stage 4 in the first sleep cycle following LE heating. Heating just prior to sleep also resulted in a substantial reduction in the duration of the first rapid eye movement sleep period. Sleep onset time was reduced by heating, particularly EE heating. The results indicate that body heating induces temporary changes that affect sleep propensity and both the quantity and temporal distribution of delta activity in the sleep EEG.

Adult↗
PubMed1988

Interactive effects of physical work and carbon monoxide on cognitive task performance.

The simple and interactive effects of carbon monoxide (CO) exposure and prior physical work on cognitive performance were evaluated in 11 men and 7 women. Three levels of carboxyhemoglobin (HbCO) (0, 7, 10%) and three workloads (rest, 35%, 60% Vo2max) were crossed resulting in nine repeated measures conditions for each subject. Following bolus administration of CO, subjects exercised or rested for 50 min, then performed five cognitive tasks: Manikin spatial processing, Sternberg memory, Stroop word-color interference, visual search, and dual-axis tracking, with and without a secondary mathematics task. Carboxyhemoglobin levels were assessed after bolus administration and again following completion of the last task. Ambient CO levels were set to maintain the required HbCO levels in each condition. Performance on the second of two sequentially presented Stroop interference tasks (using identical stimuli but with instructions reversed) was impaired with increasing HbCO level, suggesting a reduced ability to adapt to a new response set. An interaction between HbCO level and exercise level was seen for visual search performance: in rest conditions, performance was improved with increasing HbCO level; by contrast, performance was impaired with increasing HbCO levels following 60% work. Elevated HbCO had no effect on spatial processing, short-term memory, simple reaction time, or psychomotor tracking.

Adolescent↗
PubMed1987

Cardiovascular function during sleep of active older adults and the effects of exercise.

Cardiovascular function during sleep was studied in 14 (6 males, 8 females) healthy, active, older adults (57-70) years). Noninvasive measures of stroke volume (SV), heart rate (HR), cardiac output (CO), pre-ejection period (PEP), and left ventricular ejection time (LVET) were taken using impedance cardiography and computer-based "ensemble" averaging. Data were obtained from the last of three nights of normal sleep and on a night following an hour walk on a treadmill at 60% VO2 max. Cardiovascular measures revealed patterns during sleep which parallel those seen in younger subjects, i.e. a progressive decline in SV and CO, unaffected by EEG sleep stage. The trend was different for heart rate, which showed only an initial decline at sleep onset. No consistent trends were seen for LVET, whereas PEP declined to a low point 1.5 h after sleep onset. Following exercise, HR was slightly elevated during the first 3 h of sleep. In contrast, SV and CO were reduced during the period of sleep between 1 and 4 h after sleep onset; this difference was observed primarily in the women (N = 8). The results suggest that an acute increase in daily activity of older adults induces only minor changes in nocturnal cardiac function.

Aged↗
PubMed1986

Evaluation of a filter/integrator system for quantifying delta activity in the sleep electroencephalogram.

The integrated output of a delta bandpass filter was evaluated as a means of quantifying delta activity in the sleep electroencephalogram (EEG). Total integrated slow wave amplitude (ISWA) and a density measure (ISWA/20-s epoch) were determined from four complete NREM sleep periods (NREMPs) on each of 2 baseline nights from 15 subjects. Total ISWA displays a linear decline across NREMPs, whereas ISWA/20-s epoch shows a curvilinear decline. Both measures show highly significant correlations with manually staged slow wave sleep and a high degree of intra-individual consistency between nights, for both whole-night values and those of individual NREMPs. The slow-wave density index (ISWA/20-s epoch) demonstrated consistently higher between-night correlations across NREMPs than did the total ISWA index, particularly in the first NREMP, suggesting it may better characterize the nightly distribution of delta activity in an individual's sleep EEG.

Delta Rhythm↗
PubMed1985

Effects of body heating during sleep interruption.

This study assessed the effects that elevating body temperature had on sleep structure in the third and fourth sleep cycles, cycles typically characterized by a high propensity for REM sleep and diminished levels of delta amplitude and incidence. The sleep of eight women and two men was interrupted for 30 min on each of 3 consecutive nights following an undisturbed adaptation night. The subjects were awakened each night following the end of the second REM sleep period. On 2 nights, subjects were immersed to midthorax in water at either 34 degrees C (TW condition) or 41 degrees C (HW condition) for 20 min. A third interruption without immersion (NW condition) was performed to provide a second type of baseline condition. The HW condition induced a mean tympanic temperature rise of 2.5 degrees C, that returned to baseline levels in approximately 60 min. Analysis of sleep patterns focused on the two sleep cycles following interruption. The mean of the two baseline conditions (TW + NW/2) was compared with the HW condition. Sleep onset latency, REM latency, REM duration, and eye movement activity in REM were unaffected by heating. Heating evoked increases in both total NREM and slow wave sleep, though these increases were delayed until the second cycle following sleep onset (i.e., appearing in the fourth, but not the third, NREM period). These were paralleled by increases in two objective measures of delta activity: integrated slow-wave amplitude (33% increase) and slow-wave density (10% increase).

Adult↗
PubMed1985

Effects of exhaustive submaximal exercise on cardiovascular function during sleep.

The influence of an afternoon bout of exhaustive submaximal exercise on cardiovascular function and catecholamine excretion during sleep was examined in five female and four male subjects. Subjects walked on a treadmill for successive 50-min periods at 50, 60, and 70% maximal O2 consumption, separated by 10-min rest periods. Exercise terminated with volitional exhaustion. Following an adaptation night, electroencephalographic and impedance cardiographic measures were obtained during three successive nights of sleep, with exercise preceding night 3. Relative to the base-line night (night 2), exhaustive exercise resulted in a sustained elevation of heart rate and cardiac output throughout the entire night's sleep. The magnitude of these elevations was unaffected by sleep stage but decreased over the night. The typical pattern of circadian decline in cardiac output was unaltered. However, the decline in heart rate with sleep onset was greater on the exercise night. Changes in impedance dZ/dt and R-Z interval suggested an enhanced myocardial contractility during the first 3 h of sleep postexercise. Analysis of morning urine samples revealed that in seven of nine subjects norepinephrine excretion increased, epinephrine excretion decreased, and dopamine excretion was unchanged during sleep on the exercise night. It is suggested that these cardiac changes reflect a sustained increase in myocardial beta-receptor activity.

Adult↗
PubMed1984

Sleep interruption and exercise.

Five men and five women participated in a study comparing the effects of sleep interruption with and without the imposition of physical activity. Subjects were awakened following the second REM period and returned to sleep 1 h later. In the IS condition they sat up and read during this period; in the ISE condition they exercised for 50 min at 60% VO2max. Relative to undisturbed sleep (US), IS resulted in a substantially shortened third non-REM (NREM) period, increased eye movement (EM) duration and density in the third REM period, and increased slow-wave sleep (SWS) in the fourth NREM period. The loss of delta sleep in the shortened NREM period was compensated for by an increase in delta sleep in the fourth NREM period (r = -0.90). However, total SWS obtained after interruption was unchanged from US. The ISE condition induced increases in cardiac output and temperature during sleep. No consistent changes in SWS were observed relative to IS, but the duration of the third REM period was reduced as well as EM duration and density within that REM period. Since REM sleep propensity is typically highest during the metabolic nadir of early morning sleep, the suppression of tonic and phasic components of REM sleep after ISE was concluded to result from the exercise-induced increase of metabolism and body temperature during sleep.

Adult↗
PubMed1983

Nocturnal sleep, cardiovascular function, and adrenal activity following maximum-capacity exercise.

Eight subjects performed a treadmill test of their maximal aerobic capacity (VO2max) to determine whether exercise which is maximally stressful but relatively low in total energy expenditure may affect nocturnal sleep. The test was performed at 16.00 h on day 3 of the study, with day 1 as adaptation, day 2 as baseline and day 4 as a carryover night. Changes observed after exercise included a decrease in the duration of the first REM sleep period, an elevation of heart rate in the first 2 h of sleep, a reduction in norepinephrine excretion and an increased excretion of dopamine. Comparisons of sleep alterations in 4 subjects who exercised regularly (active group) with 4 subjects who took no regular exercise revealed differences in the first sleep cycle. Active subjects displayed an increased duration of SWS coupled with an increased latency to first REM onset. Non-active subjects, by contrast, displayed a shortened REM latency and duration of SWS. These results indicate that short-term maximum exercise may induce significant alteration of the temporal distribution of SWS with differences in response seen between regular exercisers and non-exercisers.

Adrenal Glands↗
PubMed1982

Components of visual attentiveness in suppression of the occipital alpha rhythm.

This study examined whether either visual input or "attention" exerts an influence on the alpha rhythm beyond that produced by oculomotor maneuvers such as movement and fixation. Alpha-suppressive effects of an attentional "set" were demonstrated in subjects anticipating a response to an unknown visual stimulus in the dark. In a second condition, subjects moved their eyes laterally between two visual targets. When visual input was increased by interspersing additional lights between the targets, a significant increase in alpha suppression was observed beyond that produced by eye movement alone. In the third condition, subjects fixated on a point of light (to stabilize oculomotor influences across tasks) while adjacent points were displayed at random intervals. Attentional "demand" was varied by requiring subjects alternately to respond to these flashing lights or passively view them. Both tasks produced alpha block relative to baseline periods, but relative suppression did not differ between tasks.

Alpha Rhythm↗
PubMed1980

Individual differences in alpha rhythm responsivity: inter-task consistency and relationships to cardiovascular and dispositional variables.

Individual differences in EEG alpha rhythm responsivity were examined with respect to: (1) consistency of response across cognitive tasks; (2) relationships to cardiovascular responsivity; and (3) relationships to dispositional variables. Inter-task correlations revealed a significant degree of stability in subjects' alpha responses to four "sensory rejection" tasks: mental arithmetic, time estimation and imagining oneself as cold or warm. Individuals evidencing greater suppression of alpha activity during mental arithmetic also displayed greater heart rate increase and greater digital vasoconstriction, as well as obtaining higher scores on the Activity subscale of the EASI-III Temperament Survey and on the "Hard Striving" subscale of the Jenkins Activity Survey for Health Prediction, a measure of the Coronary-Prone Behavior Pattern. Alpha responsivity in the time estimation and warm imagery tasks was also associated with greater heart rate increase. The results suggest that alpha responsivity is related to individual differences affecting one's attentiveness or involvement in experimental tasks.

Alpha Rhythm↗