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Biomedical subjects

Daniel F Kripke

Publications and source records attributed to Daniel F Kripke.

At least 19 recordsLinked to original sources
PubMed2004

Ethnicity, sleep, mood, and illumination in postmenopausal women.

BACKGROUND: This study examined how ethnic differences in sleep and depression were related to environmental illumination and circadian rhythms. METHODS: In an ancillary study to the Women's Health Initiative, 459 postmenopausal women were recorded for one week in their homes, using wrist monitors. Sleep and illumination experience were estimated. Depression was self-rated with a brief adjective check list. Affective diagnoses were made using the SCID interview. Sleep disordered breathing was monitored with home pulse oximetry. RESULTS: Hispanic and African-American women slept less than European-American women, according to both objective recordings and their own sleep logs. Non-European-American women had more blood oxygen desaturations during sleep, which accounted for 26% of sleep duration variance associated with ethnicity. Hispanic women were much more depressed. Hispanic, African-American and Native-American women experienced less daily illumination. Less daily illumination experience was associated with poorer global functioning, longer but more disturbed sleep, and more depression. CONCLUSIONS: Curtailed sleep and poor mood were related to ethnicity. Sleep disordered breathing was a factor in the curtailed sleep of minority women. Less illumination was experienced by non-European-American women, but illumination accounted for little of the contrasts between ethnic groups in sleep and mood. Social factors may be involved.

Black or African American↗
PubMed2004

Comparison of the nocturnal effects of once-daily timolol and latanoprost on intraocular pressure.

PURPOSE: To compare the nocturnal effects of once-daily timolol and latanoprost on intraocular pressure (IOP) in patients with ocular hypertension or early glaucomatous changes. DESIGN: Prospective, open-label, experimental study with crossover design. METHODS: Eighteen patients with ocular hypertension or early glaucomatous changes (aged 41 to 79 years) each received topical treatments with timolol (0.5% Timoptic-XE), latanoprost (0.005% Xalatan), and no IOP-lowering medication, for at least 4 weeks. Timolol was given once in the morning upon awakening and latanoprost once in the evening at bedtime. At the end of each treatment period, the patient was housed in a sleep laboratory for 24 hours and IOP was measured every 2 hours using a pneumatonometer. Measurements were taken sitting and supine during the 16-hour diurnal/wake period and only supine during the 8-hour nocturnal/sleep period. Mean diurnal and nocturnal IOP levels were compared among the treatments with timolol, latanoprost, and no medication. RESULTS: In the diurnal period, the mean IOP under the timolol or the latanoprost treatment was significantly less than the mean IOP under no medication in both the sitting and the supine positions. There was no statistical difference between the timolol and latanoprost treatments. In the nocturnal period, supine IOP with timolol treatment was not different from the supine IOP with no medication but was significantly higher than supine IOP with the latanoprost treatment. CONCLUSION: Although both once-daily timolol and latanoprost were effective in lowering IOP during the diurnal period, only latanoprost reduced IOP during the nocturnal period.

Adult↗
PubMed2004

Long sleep and mortality: rationale for sleep restriction.

Epidemiologic studies have consistently shown that sleeping >8 h per night is associated with increased mortality. Indeed, the most recent American Cancer Society data of 1.1 million respondents showed that sleeping longer than 7.5 h was associated with approximately 5% of the total mortality of the sample. The excess mortality was found even after controlling for 32 potentially confounding risk factors. Although epidemiologic data cannot prove that long sleep duration causes mortality, there is sufficient evidence to warrant future testing of the hypothesis that mild sleep restriction would decrease mortality in long sleepers. Sleep restriction might resemble dietary restriction as a potential aid to survival. Sleep restriction has several potential benefits besides possible enhanced survival. Acute sleep restriction can have dramatic antidepressant effects. Also, chronic sleep restriction is perhaps the most effective treatment for primary insomnia. Conversely, spending excessive time in bed can elicit daytime lethargy and exacerbate sleep fragmentation, resulting in a vicious cycle of further time in bed and further sleep fragmentation. Sleep restriction may be most beneficial for older adults, who tend to spend excessive time in bed and have more sleep fragmentation compared with young adults.

Aging↗
PubMed2004

Naps and circadian rhythms in postmenopausal women.

BACKGROUND: Napping patterns and relationships among naps, circadian rhythms, and nocturnal sleep were evaluated in postmenopausal women. Naps and nocturnal sleep were compared between depressed women and healthy volunteers. METHODS: The study included 436 postmenopausal women between the ages of 50 and 81 years. Psychiatric interviews were conducted using the Structured Clinical Interview for DSM-IV Axis I Disorders. Each participant wore a wrist-activity monitor and kept a daily sleep log at home for 1 week. The major urinary melatonin metabolite (6-sulfatoxymelatonin [aMT6s]) was measured for two 24-hour periods at home. RESULTS: There was no significant difference in naps and nocturnal sleep patterns between depressed participants (n = 30) and those with no history of mental disorder (n = 222). Three peaks occurred in the timing of napping: approximately 1 hour before bedtime, 8 to 9 hours after wake-up time, and 2 hours after waking, in descending order of magnitude. Significant inverse correlations were observed between evening nap duration and both wake-up time and aMT6s acrophase. The onset time of aMT6s excretion was advanced by 32 minutes in evening nappers. CONCLUSIONS: Evening napping, a characteristic of these postmenopausal women, may be related to an advance of circadian rhythms in this age group. Relationships between evening napping and earlier wake-up time may be a common manifestation of advanced circadian rhythms or may be a homeostatic effect.

Aged↗
PubMed2004

Menopause: neuroendocrine changes and hormone replacement therapy.

OBJECTIVE: We evaluated the effects of hormone replacement therapy (HRT) alone and in combination with a selective serotonin reuptake inhibitor on mood, cognition, and neuroendocrine parameters in peri- and postmenopausal women. METHODS: We measured neuroendocrine variations in peri- and postmenopausal depressed patients (DP) and postmenopausal normal control (NC) women (45 to 72 years old) before and after treatment with HRT alone and HRT combined with antidepressant medication. All subjects were without significant medical illness and off psychoactive or other medication that would interfere with neuroendocrine measures. RESULTS: Menopausal DP women reported greater severity of hot flashes, were less likely to be "morning" types, and had relatively good neuropsychological function compared with NC. DP and NC had comparable levels of reproductive hormones, with the exception of elevated prolactin levels, which increased, as did thyroid-stimulating hormone levels, in response to estradiol treatment. DP had poor sleep quality as measured both by subjective ratings and objective polysomnographic measures compared with NC. In DP estradiol did not enhance the effect of antidepressant alone on mood ratings. CONCLUSION: These findings may differ from other reports in the literature as a function of diagnoses of major depressive episode, randomized controlled trials, or dose and preparation of HRT. Further work is needed on the differential effect of treatment regimens in these disturbances that are evident primarily in baseline neuroendocrine function.

Affect↗
PubMed2003

Measurement of illumination exposure in postpartum women.

BACKGROUND: Low levels of light exposure at critical times are thought to cause seasonal affective disorder. Investigators, in studies demonstrating the usefulness of bright light therapy, also have implicated light's role in non-seasonal depression. The precise cause of postpartum depression has not been delineated, but it seemed possible that new mothers would spend reduced time in daylight. The goal of this study was to examine the levels of illumination experienced by postpartum mothers and to discover any relationship between light exposure and mood levels experienced during the postpartum period. METHODS: Fifteen postpartum women, who did not have any baseline indication of depression, wore a wrist device (Actillume) for 72 hours to measure their exposure to light. At the end of the recording period, they completed a self-reported measure of mood. The mean light exposure of these postpartum women (expressed as the 24-hour average logarithm of illumination in lux) was compared with that of a representative sample of women of comparable age, residence, and seasonal months of recording. Mood levels were then rank-ordered and tested for correlation with light exposure levels. RESULTS: There was no significant difference between the amount of light [log10lux] experienced by postpartum (1.01 SD 0.236) and control women (1.06 SD 0.285). Mood was not correlated with illumination in the postpartum sample. CONCLUSIONS: Postpartum women in San Diego did not receive reduced light, nor was low mood related to low illumination.

Adult↗
PubMed2003

Melatonin excretion with affect disorders over age 60.

Numerous studies have reported low melatonin secretion in depression, but other studies have suggested no deficit or an increase. Alterations of circadian phase or duration of melatonin secretion have also been described. Since melatonin secretion decreases as we age, it seemed interesting to examine melatonin and depression in an aging sample. Volunteers who complained of mood or sleep problems were recruited for studies in which fractional urine specimens were collected for 24 h, both at home and in the laboratory. The major metabolite, 6-sulfatoxymelatonin (aMT6s), was determined by radioimmunoassay. Of 72 volunteers aged 60-78 years, seven had current major depression and 55% had a lifetime history of an affective disorder. A 55-fold range of home aMT6s excretion rates was observed. A lifetime history of any affective disorder was significantly associated with greater log(10)[mesor] aMT6s excretion in home collections and laboratory collections, but current affective disorders were neither significantly related to melatonin excretion nor to aMT6s acrophase timing, onset, offset or duration. These results are only weakly consistent with a photoperiodic hypothesis of depression.

Aged↗
PubMed2003

Luteinizing hormone following light exposure in healthy young men.

Urinary luteinizing hormone (LH) and the melatonin metabolite (6-sulfatoxymelatonin; aMT6s) were measured in normal young men following early morning light exposure. Eleven young healthy men ages 19-30 years participated in this study. During separate weeks in counterbalanced order, each subject received both 5 days of bright light treatment (BL) and 5 days of placebo light treatment (PL) for 1 h (05:00-06:00). LH excretion was increased 69.5% after bright light exposure, but was not changed by placebo light exposure. The acrophases and offsets of aMT6s were advanced, but the duration of aMT6s excretion was not changed after BL. Light stimulation of LH could have interesting applications in psychiatry and reproductive endocrinology.

Adult↗
PubMed2003

No association of sleep with total daily physical activity in normal sleepers.

The aim of two studies was to examine both between-subjects and within-subjects associations between daily amounts of physical activity and sleep in the home environment. Study 1 examined self-reported exercise durations and sleep diaries for 105 consecutive days in 31 college students who were normal sleepers. Between-subjects associations of mean exercise with mean sleep were assessed with Spearman rank-order correlations. Within-subjects correlations were determined across 105 days, and by comparing sleep on the 11 most active vs. the 11 least active days. Study 2 examined 71 physically active adults (n=38 ages 18-30 years, and n=33 ages 60-75 years), the majority of whom were normal sleepers. Over seven consecutive days, physical activity was assessed via actigraphy and a diary-derived estimate of energy expenditure, and sleep was assessed via actigraphy and sleep diaries. Between-subjects associations of mean physical activity with mean sleep were assessed with partial correlations, controlling for age. Within-subjects associations were assessed with ANCOVAs, with daily physical activity serving as the covariate, and by comparing sleep on the most active vs. the least active day. No significant within-subjects associations between physical activity and sleep were found in the main analyses of either study. Two small, but significant, between-subjects correlations between different physical activity measures and subjective sleep were found in Study 2. These results fail to support epidemiologic data on the value of exercise for sleep, but are consistent with experimental evidence showing only modest effects of exercise on sleep.

Adolescent↗
PubMed2003

Factor structure and measurement invariance of the Women's Health Initiative Insomnia Rating Scale.

As part of the Women's Health Initiative Study, the 5-item Women's Health Initiative Insomnia Rating Scale (WHIIRS) was developed. This article summarizes the development of the scale through the use of responses from 66,269 postmenopausal women (mean age = 62.07 years, SD = 7.41 years). All women completed a 10-item questionnaire concerning sleep. A novel resampling technique was introduced as part of the data analysis. Principal-axes factor analysis without iteration and rotation to a varimax solution was conducted for 120,000 random samples of 1,000 women each. Use of this strategy led to the development of a scale with a highly stable factor structure. Structural equation modeling revealed no major differences in factor structure across age and race-ethnic groups. WHIIRS norms for race-ethnicity and age subgroups are detailed.

Age Factors↗
PubMed2003

Reliability and validity of the Women's Health Initiative Insomnia Rating Scale.

The reliability and construct validity of the 5-item Women's Health Initiative Insomnia Rating Scale (WHIIRS) were evaluated in 2 studies. In Study 1, using a sample of 66,269 postmenopausal women, validity of the WHIIRS was assessed by examining its relationship to other measures known to be related to sleep quality. Reliability of the WHIIRS was estimated using a resampling approach; the mean alpha coefficient was .78. Test-retest reliability coefficients were .96 for same-day administration and .66 after a year or more. Correlations of the WHIIRS with the other measures were in the predicted directions. Study 2 used a sample of 459 women and compared the WHIIRS with objective indicators of sleep quality. Results showed that differences in the objective indicators could be detected by the WHIIRS. Findings suggest that a between-group mean difference of approximately 0.50 of a standard deviation on the WHIIRS may be clinically meaningful.

Aged↗
PubMed2003

Actigraphy suggests age-related differences in napping and nocturnal sleep.

The aim of this study was to contrast the time distribution of out-of-bed napping in young and older adults through recordings of wrist activity, and to evaluate the correlates of napping with nocturnal sleep. Seventy-three young adults between 18 and 32 years and 60 older adults between 60 and 75 years of age participated in the study. Subjects were selected for good general health and had few sleep complaints. They wore wrist-activity monitors and kept daily sleep logs for 1 week. Automatic sleep scoring was edited by the authors, supplemented by sleep logs and illumination data as well as activity data. Napping episodes were modestly increased in older adults, but there was no difference in the daily duration of napping. Older adults napped more in the evening (especially within 2 h before bedtime), whereas young adults napped more in the afternoon. The older adults with evening naps (n = 31) showed earlier nocturnal wake-up times and decreased nocturnal sleep duration compared with the older adults without evening naps (n = 29). There was no difference in nocturnal sleep between young adults with afternoon naps (n = 32) and without afternoon naps (n = 41). In determining the effects of napping on nocturnal sleep, timing of napping and age are important. Maintaining alertness during the evening (e.g. by bright light exposure or moderate exercise) would be a possible approach to delay wake-up times in older adults.

Adolescent↗
PubMed2003

Age-related changes of circadian rhythms and sleep-wake cycles.

OBJECTIVES: To compare relationships between the sleep-wake cycle and endogenous circadian rhythms in young and older adults and to examine correlates between evening naps and circadian rhythms in older adults. DESIGN: For 1 week of home recording, subjects wore wrist-activity monitors and kept daily sleep logs. After the home monitoring, subjects entered the laboratory on a 90-minute sleep-wake schedule and were monitored on this schedule for at least 30 hours. SETTING: Community living and laboratory. PARTICIPANTS: Sixty-seven young adults, aged 18 to 32, and 56 older adults, aged 60 to 75, who were healthy and had few sleep complaints. MEASUREMENTS: Times of nocturnal sleep, out-of-bed napping, and illumination were obtained at home. Sleep propensity and oral body temperature (OBT) were measured in the laboratory, along with circadian rhythms of cortisol and 6-sulfatoxymelatonin (aMT6s, assayed from urine samples collected every 90 minutes). RESULTS: Home sleep times and illumination acrophases (fitted peak times) were advanced in older adults. The phase angles (time intervals) between onset of aMT6s and sleep onset were not changed in older adults, but sleep offset was more advanced than acrophase and offset of aMT6s with aging. Acrophases of cortisol and sleep propensity were advanced in older adults to the same extent as sleep times, but OBT was less advanced than sleep times. Older adults who took evening naps showed more advanced sleep offset and circadian rhythms of aMT6s, but there were no differences in the phase angles of sleep onset and circadian rhythms of aMT6s and cortisol compared with older adults who did not take evening naps. CONCLUSION: Measuring different circadian markers suggested different phase relationships between the sleep-wake cycle and endogenous circadian rhythms in aging. Early awakening in older adults cannot be explained simply by a relative phase advance of the circadian system. Evening naps and advanced illumination may play a role in the advance of the circadian system in aging.

Adolescent↗
PubMed2003

PRC bisection tests.

This communication presents a new method for evaluating phase response curves (PRCs). A PRC describes the phase shifts produced in an oscillator by stimuli applied at different initial phase-states of that oscillator. In the PRC bisection tests, we repeatedly cut in half the circular distribution of the initial phase-states of the oscillator when stimuli are given. Empirically, we locate that optimal diameter which best bisects the circular distribution of phase responses into arcs of relative phase advance and phase delay. We compute a D score reflecting the success of the best bisection. The null hypothesis of a random distribution of phase responses by initial phase is tested with a Monte Carlo procedure, which computes Dr scores from random combinations of phase shifts with initial phases, thus determining the probability, given the null hypothesis, that the observed D score was from a random distribution. The bisection procedure can be extended to examine whether stronger phase shifts are produced in one phase response curve than in contrasting curves. Also, the bisection procedure yields an estimate of the inflection point of the phase response curve. A method is given to estimate the power of the PRC bisection test.

Animals↗