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Biomedical subjects

D F Kripke

Publications and source records attributed to D F Kripke.

At least 91 records · Page 5Linked to original sources
PubMed1989

Sleep fragmentation in patients from a nursing home.

Institutionalized elderly persons are said to have very disturbed sleep, yet few studies have collected empirical data on the sleep of these patients. We recorded sleep in 200 patients (131 females and 69 males; mean age = 81.9 years, SD = 8.6) in a skilled nursing facility. A modified Respitrace-Medilog portable recording system was used. In recordings averaging 15.4 hours, the patients were asleep for 7 hours, 58 minutes and awake for 7 hours, 28 minutes. To obtain that amount of sleep, the patients spent an extended time in bed during the day, for they averaged no more than 39.5 minutes of sleep per hour in any hour of the night, and 50% woke up at least 2 to 3 times per hour. In summary, although nursing home patients slept on average only one hour longer than independently living elderly, they had to spend substantially more time in bed to obtain the same amount of sleep.

Activity Cycles↗
PubMed1989

Apnea revisited: a longitudinal follow-up.

Volunteers aged 65 years and over who were previously studied underwent follow-up interviews and sleep recordings several years later (mean follow-up, 4.6 years). Modest correlations between the initial and subsequent recordings were found for apnea index, hypopnea index, and respiratory disturbance index. Sleep apnea indices did not increase over time; however, individual subjects showed great variability in amount of apnea. Periodic leg movement indices, on the other hand, significantly increased. Subjective reports indicated a significant increase in the amount of time spent awake and a significant decrease in the amount of loud snoring.

Aged↗
PubMed1989

Bright light can delay human temperature rhythm independent of sleep.

New evidence suggest that the phase of human circadian (approximately 24 h) rhythms can be reset by exposures to bright artificial light. This study explored the value of 5 h of bright 3,800-6,000 lx light in resetting human circadian rhythm phases among healthy volunteers. Nine subjects were exposed to 3-5 h bright light for three evenings and to control dim light for an equivalent time, in counterbalanced orders. Electroencephalogram sleep recordings, overnight rectal temperature measurements, and mood scales were obtained. Compared with control dim light, bright light delayed the body temperature rhythm approximately 3 h; however, sleep latency was delayed only 9 min. This suggests that bright light shifted the phase of the human circadian temperature rhythm independent of its effects on sleep phase. Resetting rhythms with bright light may prove useful in treatment of psychiatric disorders.

Adolescent↗
PubMed1989

Phototherapy for depressive disorders: a review.

The use of bright light (phototherapy) for psychiatric disorders has recently generated much interest among researchers and the lay population. The authors review the treatment studies of phototherapy for seasonal and non-seasonal depressive disorders, and the empirical evidence for theories of the psychophysiology of phototherapy. Although its mechanism of action remains to be explained, phototherapy appears to be a safe and effective treatment for seasonal depression and a promising treatment for non-seasonal depression. Further questions and future research directions are presented.

Depressive Disorder↗
PubMed1989

Sleep apnea in female patients in a nursing home. Increased risk of mortality.

There has been much speculation on the risk of mortality associated with sleep apnea. We followed-up 233 elderly patients in nursing homes, 70 percent of whom had five or more respiratory disturbances per hour of sleep, to determine if sleep apnea is a predictor of mortality. Cox proportional hazards survival analyses indicated a gender effect, with women having a much better survival rate than men. In women, but not in men, there was a strong association between mortality and the RDI. In addition, patients with obstructive sleep apnea had a greater tendency to die in their sleep. These results show that respiratory disturbances in sleep are an extremely significant risk factor for mortality in elderly women who are in poor health.

Aged↗
PubMed1989

Gender differences in the circadian temperature rhythms of healthy elderly subjects: relationships to sleep quality.

Body core temperature and subjective sleep quality were measured in 22 healthy elderly men and women while they lived at home and continued their normal daily activities. The acrophase of body temperature was phase-advanced by an average of 1.25 h in the older women compared to the age-matched men. Habitual bedtimes did not differ between men and women, but usual wakeup time and average sleep duration did: women awakened earlier and slept for shorter durations. Women were also less satisfied with their sleep than were the men. For the group, the acrophase of body temperature was significantly positively correlated with habitual bedtime and wakeup time. These data support the notion that age-related changes in the circadian timing system are, in large part, gender-dependent. The findings are also consistent with the hypothesis that alterations in sleep timing and quality that typically accompany aging are closely tied to age-related changes in circadian physiology.

Aged↗
PubMed1988

Exposure to light in healthy elderly subjects and Alzheimer's patients.

Exposure to light was recorded from 10 healthy elderly adults and 13 age-matched subjects with senile dementia of the Alzheimer's type (SDAT). Data were recorded in the home, for an average of 5 days, while subjects continued their normal daily activities. Subjects were exposed to remarkably small intervals of illumination exceeding 2000 lux. Subjects with SDAT were exposed to bright light significantly less than healthy controls (0.5 vs. 1.0 hr). Whether or not they had SDAT, males were exposed to illumination exceeding 2000 lux significantly more than were females. Healthy elderly received about two-thirds the duration of bright light received by healthy younger subjects. These findings suggest an association between decreased exposure to bright light and the declines in sleep quality which typically accompany normal and pathological aging.

Aged↗
PubMed1987

Potassium reduces lithium toxicity: circadian rhythm actions are maintained.

We tested whether a high potassium diet alters lithium's effects on locomotor activity rhythms to the same extent as it prevents lithium toxicity. Rats fed a standard diet containing 0.47% potassium lost weight after subcutaneous implantation of an osmotic pump delivering 1.35 mg of lithium chloride per hour, and most died or became sick within three weeks after implantation. In contrast, all rats fed a diet containing 4.1% potassium gained weight at the same rate regardless of whether they had received lithium infusions or placebo. In a second experiment, lithium administration by either diet or osmotic pump delayed wheel running rhythms, showing that lithium's central nervous system action did not depend on potassium intake or method of lithium administration. Dietary potassium supplementation may provide a useful strategy for improving the therapeutic index of lithium treatment.

Animals↗
PubMed1987

When people die. Cause of death versus time of death.

A sample of 4,920 disease-related deaths from New York City for 1979 (8.7 percent of all relevant data from New York City's files) showed a 60 percent rise in death rate beginning at 2 A.M. and reaching a peak at 8 A.M. A smaller peak was also noted at 6 P.M. The rise in human mortality beginning at 2 A.M. and peaking at 8 A.M. might be explained by: artifact of deaths occurring anytime during the night that are discovered after daybreak, effect of less efficient health care between 2 A.M. and 8 A.M., and disease processes that somehow increase risk of death between 2 A.M. and 8 A.M. An attempt was made to differentiate among these possibilities by comparing time of death for various subsamples. The bimodal pattern appeared only in the temporal distribution of deaths of persons over 65 years of age; deaths of persons under 65 did not show significant temporal concentration. There were also prominent differences in the distribution of deaths for different reported causes of death. Ischemic heart disease, which numerically accounted for over 50 percent of the sample, showed peak mortality at 8 A.M. for both males and females. Hypertensive disease showed a significant peak in mortality at 1 A.M. for females only. Cerebrovascular disease peaked significantly at 6 A.M. with a significant peak only for males. The age and disease specificity of the 2 A.M. to 8 A.M. rise in death is consistent with a disease-related explanation for the bimodal circadian pattern in mortality. The quality and efficiency of health care could be improved with more precise information on peak periods of risk for specific morbid conditions.

Aged↗
PubMed1987

Characteristics of obstructive and central sleep apnea in the elderly: an interim report.

Home sleep recordings were done on 358 randomly selected elderly volunteers (mean age 72.4). When men and women were combined, 62 (17%) had predominantly obstructive sleep apnea, 21 (6%) had predominantly central sleep apnea, and 3 (1%) had mixed sleep apnea. Although the prevalence of sleep apnea in women does increase after menopause, sleep apnea was still significantly more common in older men (31%) than in older women (19%). There were no significant differences in age among groups with different types of apnea. There was a significant correlation of age with increasing apnea index within the obstructive sleep apnea group. Elderly volunteers with central sleep apnea had more midsleep awakenings. Elderly volunteers with obstructive sleep apnea had longer apneas. Unlike previous studies, we found many similarities and only modest differences in the presentations of central and obstructive sleep apnea.

Age Factors↗
PubMed1986

Natural light exposure of young adults.

Bright light has a role in natural coordination of mammalian circadian and seasonal rhythms. In humans, the light intensity must probably exceed 2000 lux to be optimal. Natural light exposures of 10 healthy adults were measured over a 24-hour period, using forehead illumination transducers connected to a portable computer. The subjects varied markedly in duration and timing of exposures to light greater than 2000 lux. On average, the subjects experienced bright light for only 90 minutes per day, less than the 3-8 hours of bright light necessary to maximally synchronize human circadian rhythms. These results suggest that natural and artificial light exposure for many Americans may be suboptimal for circadian and seasonal synchronization.

Adult↗
PubMed1986

Body position changes and periodic movements in sleep.

What triggers episodes of periodic movements in sleep (PMS) remains unknown. Despite the uncertainties, there is no doubt of the widespread prevalence of PMS, particularly in elderly populations. This study explored possible consistent temporal relationships between body position and PMS episodes. Eleven subjects, monitored by polygraph and videotape, averaged 299 leg jerks in nine episodes, and 13 body position changes of greater than or equal to 90 degrees. Leg jerk episodes had a significant tendency to terminate soon before body position changes, and likewise there was a trend for leg jerk episodes to begin soon after position changes. It is hypothesized that adverse body positioning, via an influence upon the spinal cord or peripheral tissue perfusion, triggers PMS episodes, which persist until the adverse positions are changed. In this small sample, "adverse" positions could not be elucidated.

Adult↗
PubMed1985

Lithium effects on selected circadian rhythms in rats.

Treating rats with lithium results in clear phase-delays in certain circadian rhythms but has no effect upon other rhythms. Phase-delays can be seen in running-wheel activity rhythms but under certain conditions, phase changes are not noted in SCN 2-DG uptake or pineal melatonin rhythms.

Animals↗
PubMed1985

Sleep apnea and periodic movements in an aging sample.

Individuals 65 years of age and older were randomly selected, from a primarily white upper-class population, to participate in a study of sleep disorders in elderly adults. One hundred forty-five volunteers had a brief telephone interview, a home interview, and a portable sleep recording using the Medilog and Respitrace systems. By research classifications, we found that 18% of the elderly participants had sleep apnea (apnea index greater than 5), 34% had periodic movements in sleep (myoclonus index greater than 5) (PMS), and 10% had both sleep apnea and PMS. These were not clinical diagnoses. The home recording indicated that the individuals with PMS slept significantly less than other older adults.

Age Factors↗