Multi-ancestry genome-wide analysis identifies shared genetic effects and common genetic variants for self-reported sleep duration.

Both short (≤6 h per night) and long sleep duration (≥9 h per night) are associated with increased risk of chronic diseases. Despite evidence linking habitual sleep duration and risk of disease, the genetic determinants of sleep duration in the general population are poorly understood, especially outside of European (EUR) populations. Here, we report that a polygenic score of 78 European ancestry sleep duration single-nucleotide polymorphisms (SNPs) is associated with sleep duration in an African (n = 7288; P = 0.003), an East Asian (n = 13 618; P = 6 × 10-4) and a South Asian (n = 7485; P = 0.025) genetic ancestry cohort, but not in a Hispanic/Latino cohort (n = 8726; P = 0.71). Furthermore, in a pan-ancestry (N = 483 235) meta-analysis of genome-wide association studies (GWAS) for habitual sleep duration, 73 loci are associated with genome-wide statistical significance. Follow-up of five loci (near HACD2, COG5, PRR12, SH3RF1 and KCNQ5) identified expression-quantitative trait loci for PRR12 and COG5 in brain tissues and pleiotropic associations with cardiovascular and neuropsychiatric traits. Overall, our results suggest that the genetic basis of sleep duration is at least partially shared across diverse ancestry groups.

Addition of FFRct in the diagnostic pathway of patients with stable chest pain to reduce unnecessary invasive coronary angiography (FUSION) : Rationale and design for the multicentre, randomised, controlled FUSION trial.

BACKGROUND: Coronary computed tomography angiography (CCTA) is widely used in the diagnostic work-up of patients with stable chest pain. CCTA has an excellent negative predictive value, but a moderate positive predictive value for detecting coronary stenosis. Computed tomography-derived fractional flow reserve (FFRct) is a non-invasive, well-validated technique that provides functional assessment of coronary stenosis, improving the positive predictive value of CCTA. However, to determine the value of FFRct in routine clinical practice, a pragmatic randomised, controlled trial (RCT) is required. We will conduct an RCT to investigate the impact of adding FFRct analysis in the diagnostic pathway of patients with a coronary stenosis on CCTA on the rate of unnecessary invasive coronary angiography, cost-effectiveness, quality of life and clinical outcome. METHODS: The FUSION trial is a prospective, multicentre RCT that will randomise 528 patients with stable chest pain and anatomical stenosis of ≥ 50% but < 90% in at least one coronary artery of ≥ 2 mm on CCTA, to FFRct-guided care or usual care in a 1:1 ratio. Follow-up will be 1 year. The primary endpoint is the rate of unnecessary invasive coronary angiography within 90 days. CONCLUSION: The FUSION trial will evaluate the use of FFRct in stable chest pain patients from the Dutch perspective. The trial is funded by the Dutch National Health Care Institute as part of the research programme 'Potentially Promising Care' and the results will be used to assess if FFRct reimbursement should be included in the standard health care package.

Circadian timing and alignment in healthy adults: associations with BMI, body fat, caloric intake and physical activity.

INTRODUCTION: Disruption of circadian rhythms is one of the proposed mechanisms linking late sleep timing to obesity risk but few studies have evaluated biological markers outside of the laboratory. The goal of this study was to determine the relationship between the timing and alignment of melatonin and sleep onset (phase angle) with body mass index (BMI), body fat and obesity-related behaviors. We hypothesized that circadian alignment (relationship of melatonin to sleep timing) rather than circadian (melatonin) timing would be associated with higher BMI, body fat, dietary intake and lower physical activity. SUBJECTS/METHODS: Adults with sleep duration ⩾6.5 h completed 7 days of wrist actigraphy, food diaries and SenseWear arm band monitoring. Circadian timing, measured by dim light melatonin onset was measured in the clinical research unit. Circadian alignment was calculated as the duration between dim light melatonin onset and average sleep onset time in the prior week (phase angle). Body fat was evaluated using dual-energy X-ray absorptiometry. Data were analyzed using bivariate correlations and multivariable regression analyses controlling for age, sex, sleep duration and evening light exposure. RESULTS: Participants included 97 adults (61 F, age 26.8±7.3 years) with average sleep duration 443.7 (s.d.=50.4) minutes. Average phase angle was 2.2 h (s.d.=1.5). Circadian alignment was associated with circadian timing (P<0.001) and sleep duration (P=0.005). In multivariable analyses, later circadian timing was associated with lower BMI (P=0.04). Among males only, circadian alignment was associated with percent body fat (P=0.02) and higher android/gynoid fat ratio (P=0.04). Circadian alignment was associated with caloric intake (P=0.049) carbohydrate intake (P=0.04) and meal frequency (P=0.03) among both males and females. CONCLUSION: Circadian timing and alignment were not associated with increased BMI or body fat, among healthy adults with ⩾6.5 h of sleep, but circadian alignment was associated with dietary intake. There may be sex differences in the relationship between circadian alignment and body fat.

Pervasive, yet idiosyncratic, epistatic pleiotropy during adaptation in a behaviourally complex microbe.

Understanding how multiple mutations interact to jointly impact multiple ecologically important traits is critical for creating a robust picture of organismal fitness and the process of adaptation. However, this is complicated by both environmental heterogeneity and the complexity of genotype-to-phenotype relationships generated by pleiotropy and epistasis. Moreover, little is known about how pleiotropic and epistatic relationships themselves change over evolutionary time. The soil bacterium Myxococcus xanthus employs several distinct social traits across a range of environments. Here, we use an experimental lineage of M. xanthus that evolved a novel form of social motility to address how interactions between epistasis and pleiotropy evolve. Specifically, we test how mutations accumulated during selection on soft agar pleiotropically affect several other social traits (hard agar motility, predation and spore production). Relationships between changes in swarming rate in the selective environment and the four other traits varied greatly over time in both direction and magnitude, both across timescales of the entire evolutionary lineage and individual evolutionary time steps. We also tested how a previously defined epistatic interaction is pleiotropically expressed across these traits. We found that phenotypic effects of this epistatic interaction were highly correlated between soft and hard agar motility, but were uncorrelated between soft agar motility and predation, and inversely correlated between soft agar motility and spore production. Our results show that 'epistatic pleiotropy' varied greatly in magnitude, and often even in sign, across traits and over time, highlighting the necessity of simultaneously considering the interacting complexities of pleiotropy and epistasis when studying the process of adaptation.

Independent prognostic value of coronary artery calcium score and coronary computed tomography angiography in an outpatient cohort of low to intermediate risk chest pain patients.

BACKGROUND: Limited studies report on the additional prognostic value of coronary computed tomography angiography (CCTA) and the coronary artery calcium score (CACS). METHODS: For a median of 637 days, 1551 outpatients with chest pain, without known coronary artery disease (CAD) and low or intermediate pre-test probability of CAD, were followed for major adverse cardiac events (MACE), defined as death, myocardial infarction or late revascularisation. Cox proportional hazard regression was used to evaluate the independent prognostic value of CCTA and CACS. RESULTS: MACE occurred in 23 patients (1.5 %): death (3, 0.2 %), myocardial infarction (4, 0.3 %) and late revascularisation (16, 1.3 %). Multivariate analysis showed an independent prognostic value of CCTA (p < 0.001), CACS of 100-400 (p = 0.035) and CACS of > 400 (p = 0.021). CCTA showed obstructive CAD in 3.1 % of patients with CACS = 0. No events occurred in patients with CACS = 0 without obstructive CAD at CCTA, whereas 2/23 patients (9 %) with CACS = 0 with obstructive CAD had a MACE. CONCLUSIONS: Our study shows that both CCTA and higher CACS categories have independent prognostic value in chest pain patients with low to intermediate pre-test probability of obstructive CAD, in which CCTA is appropriate. Furthermore a non-negligible amount of patients with CACS = 0 have obstructive CAD at CCTA. CCTA can be used in these patients to identify those at risk for MACE.

The impact of atrial fibrillation on prognosis in aortic stenosis.

BACKGROUND: Atrial fibrillation (AF) and aortic stenosis (AS) are both highly prevalent and often coexist. Various studies have focused on the prognostic value of AF in patients with AS, but rarely considered left ventricular (LV) diastolic function as a prognostic factor. OBJECTIVE: To evaluate the prognostic impact of AF in patients with AS while correcting for LV diastolic function. METHODS: Patients with first diagnosis of significant AS were selected and stratified according to history of AF. The endpoint was all-cause mortality. RESULTS: In total, 2849 patients with significant AS (mean age 72 ± 12 years, 54.8% men) were evaluated, and 686 (24.1%) had a history of AF. During a median follow-up of 60 (30-97) months, 1182 (41.5%) patients died. Ten-year mortality rate in patients with AF was 46.8% compared to 36.8% in patients with sinus rhythm (SR) (log-rank P < 0.001). On univariable (HR: 1.42; 95% CI: 1.25-1.62; P < 0.001) and multivariable Cox regression analysis (HR: 1.19; 95% CI: 1.02-1.38; P = 0.026), AF was independently associated with mortality. However, when correcting for indexed left atrial volume, E/e' or both, AF was no longer independently associated with all-cause mortality. CONCLUSION: Patients with significant AS and AF have a reduced survival as compared to patients with SR. Nonetheless, when correcting for markers of LV diastolic function, AF was not independently associated with outcomes in patients with significant AS.

Prevalence and Prognostic Implications of Discordant Grading and Flow-Gradient Patterns in Moderate Aortic Stenosis.

BACKGROUND: The prognostic implications of discordant grading in severe aortic stenosis (AS) are well known. However, the prevalence of different flow-gradient patterns and their prognostic implications in moderate AS are unknown. OBJECTIVES: The purpose of this study was to investigate the occurrence and prognostic implications of different flow-gradient patterns in patients with moderate AS. METHODS: Patients with moderate AS (aortic valve area >1.0 and ≤1.5 cm2) were identified and divided in 4 groups based on transvalvular mean gradient (MG), stroke volume index (SVi), and left ventricular ejection fraction (LVEF): concordant moderate AS (MG ≥20 mm Hg) and discordant moderate AS including 3 subgroups: normal-flow, low-gradient moderate AS (MG <20 mm Hg, SVi ≥35 mL/m2, and LVEF ≥50%); "paradoxical" low-flow, low-gradient moderate AS (MG <20 mm Hg, SVi <35 mL/m2, and LVEF ≥50%) and "classical" low-flow, low-gradient moderate AS (MG <20 mm Hg and LVEF <50%). The primary endpoint was all-cause mortality. RESULTS: Of 1,974 patients (age 73 ± 10 years, 51% men) with moderate AS, 788 (40%) had discordant grading, and these patients showed significantly higher mortality rates than patients with concordant moderate AS (P < 0.001). On multivariable analysis, "paradoxical" low-flow, low-gradient (HR: 1.458; 95% CI: 1.072-1.983; P = 0.014) and "classical" low-flow, low-gradient (HR: 1.710; 95% CI: 1.270-2.303; P < 0.001) patterns but not the normal-flow, low-gradient moderate AS pattern were independently associated with all-cause mortality. CONCLUSIONS: Discordant grading is frequently (40%) observed in patients with moderate AS. Low-flow, low-gradient patterns account for an important proportion of the discordant cases and are associated with increased mortality. These findings underline the need for better phenotyping patients with discordant moderate AS.

Moderate aortic stenosis: importance of symptoms and left ventricular ejection fraction.

AIMS: The aim of this study is to investigate the independent determinants of survival in patients with moderate aortic stenosis (AS), stratified by severity of symptoms and left ventricular ejection fraction (LVEF). METHODS AND RESULTS: Patients with a first diagnosis of moderate AS (aortic valve area >1.0 and ≤1.5 cm2) were identified. Patients were stratified by New York Heart Association (NYHA) functional class (NYHA I, NYHA II, or NYHA III-IV) and LVEF (LVEF ≥60%, LVEF 50-59%, or LVEF <50%) at the time of moderate AS diagnosis. The primary endpoint was all-cause mortality, while the secondary endpoint included all-cause mortality and aortic valve replacement. Of 1961 patients with moderate AS (mean age 73 ± 10 years, 51% men), 1108 (57%) patients were in NYHA class I, while 527 (27%) and 326 (17%) patients had symptoms of NYHA class II and III-IV, respectively. Regarding LVEF, 1032 (53%) had LVEF ≥60%, 544 (28%) LVEF 50-59%, and 385 (20%) LVEF <50%. During a median follow-up of 50 (23-82) months, 868 (44%) patients died. On multivariable analysis, NYHA class II [hazard ratio (HR): 1.633; 95% confidence interval (CI): 1.431-1.864; P < 0.001], NYHA class III-IV (HR: 2.084; 95% CI: 1.797-2.417; P < 0.001), LVEF 50-59% (HR: 1.194; 95% CI: 1.013-1.406; P = 0.034), and LVEF <50% (HR: 1.694; 95% CI: 1.417-2.026; P < 0.001) were independently associated with increased mortality. CONCLUSION: Moderate AS is associated with poor long-term survival. Baseline symptom severity and LVEF are associated with worse outcomes in these patients. Patients with low-normal LVEF (<60%) and mild symptoms (NYHA II) already have an increased risk of adverse events.

Left ventricular remodelling patterns in patients with moderate aortic stenosis.

AIMS: Moderate aortic stenosis (AS) is associated with an increased risk of adverse events. Because outcomes in patients with AS are ultimately driven by the condition of the left ventricle (LV) and not by the valve, assessment of LV remodelling seems important for risk stratification. This study evaluated the association between different LV remodelling patterns and outcomes in patients with moderate AS. METHODS AND RESULTS: Patients with moderate AS (aortic valve area 1.0-1.5 cm2) were identified and stratified into four groups according to the LV remodelling pattern: normal geometry (NG), concentric remodelling (CR), concentric hypertrophy (CH), or eccentric hypertrophy (EH). Clinical outcomes were defined as all-cause mortality and a composite endpoint of all-cause mortality and aortic valve replacement (AVR). Of 1931 patients with moderate AS (age 73 ± 10 years, 52% men), 344 (18%) had NG, 469 (24%) CR, 698 (36%) CH, and 420 (22%) EH. Patients with CH and EH showed higher 3-year mortality rates (28% and 32%, respectively) when compared with patients with NG (19%) (P < 0.001). After multivariable adjustment, CH remained independently associated with mortality (HR 1.258, 95% CI 1.016-1.558; P = 0.035), whereas both CH (HR 1.291, 95% CI 1.088-1.532; P = 0.003) and EH (HR 1.217, 95% CI 1.008-1.470; P = 0.042) were associated with the composite endpoint of death or AVR. CONCLUSION: In patients with moderate AS, those who develop CH already have an increased risk of all-cause mortality. Assessment of the LV remodelling patterns may identify patients at higher risk of adverse events, warranting closer surveillance, and possibly earlier intervention.

Sex-Related Differences in Medically Treated Moderate Aortic Stenosis.

Background: Recent data showed poor long-term survival in patients with moderate AS. Although sex differences in left ventricular (LV) remodeling and outcome are well described in severe AS, it has not been evaluated in moderate AS. Methods: In this retrospective, multicenter study, patients with a first diagnosis of moderate AS diagnosed between 2001 and 2019 were identified. Clinical and echocardiographic parameters were recorded at baseline and compared between men and women. Patients were followed up for the primary endpoint of all-cause mortality with censoring at the time of aortic valve replacement. Results: A total of 1895 patients with moderate AS (age 73 ± 10 years, 52% male) were included. Women showed more concentric hypertrophy and had more pronounced LV diastolic dysfunction than men. During a median follow-up of 34 (13-60) months, 682 (36%) deaths occurred. Men showed significantly higher mortality rates at 3- and 5-year follow-up (30% and 48%, respectively) than women (26% and 39%, respectively) (p = 0.011). On multivariable analysis, male sex remained independently associated with mortality (hazard ratio 1.209; 95% CI: 1.024-1.428; p = 0.025). LV remodeling (according to LV mass index) was associated with worse outcomes (hazard ratio 1.003; CI: 1.001-1.005; p = 0.006), but no association was observed between the interaction of LV mass index and sex with outcomes. Conclusions: LV remodeling patterns are different between men and women having moderate AS. Male sex is associated with worse outcomes in patients with medically treated moderate AS. Further studies investigating the management of moderate AS in a sex-specific manner are needed.

C-reactive protein in myocardial infarction binds to circulating microparticles but is not associated with complement activation.

BACKGROUND: C-reactive protein (CRP) is elevated in patients with acute myocardial infarction (AMI). When CRP binds to membrane phospholipids or Fc receptors, it activates the complement system. Recent studies show that CRP can be exposed on cell-derived microparticles (MP) and is associated complement activation. OBJECTIVES: We studied complement activation on circulating MP in AMI patients and healthy controls. METHODS: MP were isolated from plasma of AMI patients (n=21) and sex- and age-matched healthy individuals (n=10), and analyzed by flow cytometry for bound complement components (C1q, C4, C3) and complement inhibitor and activator molecules (C4bp, CRP, serum amyloid P component, immunoglobulins IgM and IgG). Concurrently, the levels of fluid phase complement activation products and inhibitor and activator molecules were determined. RESULTS: Fluid phase CRP, MP with bound CRP (CRP + MP), and C3 activation products were elevated in AMI patients compared to controls (P=0.032, P=0.031 and P=0.023, respectively), and fluid phase CRP correlated with CRP+ MP (r=0.84, P<0.001). Although CRP+ MP were elevated, they were not associated with C1q+ MP (r=0.32, P=0.174). In contrast, IgG+ MP were associated with C1q+ MP (r=0.73, P<0.001), C4+ MP and C3+ MP (r=0.78 and r=0.87, respectively; both P<0.001), and C4bp (r=0.63, P=0.004). In healthy individuals, CRP+ MP were strongly associated with C1q+ MP (r=0.82, P=0.007), which in turn were associated with C4+ MP and C3+ MP (r=0.68, P=0.032 and r=0.68, P=0.031, respectively). CONCLUSIONS: Despite CRP-associated complement activation on the surface of MP in healthy individuals and a strong correlation between MP-bound CRP and fluid phase CRP in AMI patients, the MP-associated complement activation is IgG- but not CRP-dependent in AMI patients.

Diverging associations of an intended early invasive strategy compared with actual revascularization, and outcome in patients with non-ST-segment elevation acute coronary syndrome: the problem of treatment selection bias.

AIMS: In several observational studies, revascularization is associated with substantial reduction in mortality in patients with non-ST-segment elevation acute coronary syndrome (nSTE-ACS). This has strengthened the belief that routine early angiography would lead to a reduction in mortality. We investigated the association between actual in-hospital revascularization and long-term outcome in patients with nSTE-ACS included in the ICTUS trial. METHODS AND RESULTS: The study population of the present analysis consists of ICTUS participants who were discharged alive after initial hospitalization. The ICTUS trial was a randomized, controlled trial in which 1200 patients were randomized to an early invasive or selective invasive strategy. The endpoints were death from hospital discharge until 4 year follow-up and death or spontaneous myocardial infarction (MI) until 3 years. Among 1189 patients discharged alive, 691 (58%) underwent revascularization during initial hospitalization. In multivariable Cox regression analyses, in-hospital revascularization was independently associated with a reduction in 4 year mortality and 3 year event rate of death or spontaneous MI: hazard ratio (HR) 0.59 [95% confidence interval (CI) 0.37-0.96] and 0.46 (95% CI 0.31-0.68). However, when intention-to-treat analysis was performed, no differences in cumulative event rates were observed between the early invasive and selective invasive strategies: HR 1.10 (95% CI 0.70-1.74) for death and 1.27 (95% CI 0.88-1.85) for death or spontaneous MI. CONCLUSION: The ICTUS trial did not show that an early invasive strategy resulted in a better outcome than a selective invasive strategy in patients with nSTE-ACS. However, similar to retrospective analyses from observational studies, actual revascularization was associated with lower mortality and fewer MI. Whether an early invasive strategy leads to a better outcome than a selective invasive strategy cannot be inferred from the observation that revascularized patients have a better prognosis in non-randomized studies.

Cystatin C for enhancement of risk stratification in non-ST elevation acute coronary syndrome patients with an increased troponin T.

BACKGROUND: We assessed the value of cystatin C for improvement of risk stratification in patients with non-ST elevation acute coronary syndrome (nSTE-ACS) and increased cardiac troponin T (cTnT), and we compared the long-term effects of an early invasive treatment strategy (EIS) with a selective invasive treatment strategy (SIS) with regard to renal function. METHODS: Patients (n = 1128) randomized to an EIS or an SIS in the ICTUS trial were stratified according to the tertiles of the cystatin C concentration at baseline. The end points were death within 4 years and spontaneous myocardial infarction (MI) within 3 years. RESULTS: Mortality was 3.4%, 6.2%, and 13.5% in the first, second, and third tertiles, respectively, of cystatin C concentration (log-rank P < 0.001), and the respective rates of spontaneous MI were 5.5%, 7.5%, and 9.8% (log-rank P = 0.03). In a multivariate Cox regression analysis, the cystatin C concentration in the third quartile remained independently predictive of mortality [hazard ratio (HR), 2.04; 95% CI, 1.02-4.10; P = 0.04] and spontaneous MI (HR, 1.95; 95% CI, 1.05-3.63; P = 0.04). The mortality rate in the second tertile was lower with the EIS than with the SIS (3.8% vs 8.7%). In the third tertile, the mortality rates with the EIS and the SIS were, respectively, 15.0% and 12.2% (P for interaction = 0.04). Rates of spontaneous MI were similar for the EIS and the SIS within cystatin C tertiles (P for interaction = 0.22). CONCLUSIONS: In patients with nSTE-ACS and an increased cTnT concentration, mild to moderate renal dysfunction is associated with a higher risk of death and spontaneous MI. Use of cystatin C as a serum marker of renal function may improve risk stratification.

Increases in myeloperoxidase levels after exercise in myocardial perfusion scintigraphy are not induced by myocardial ischemia.

BACKGROUND: Increased systemic levels of myeloperoxidase (MPO) have been reported in patients with acute myocardial ischemia. We studied the association between exercise-induced myocardial ischemia measured by myocardial perfusion scintigraphy (MPS) and the magnitude and time course of changes in MPO levels in humans. METHODS: One hundred and twenty six patients underwent symptom limited exercise MPS. Myocardial ischemia was assessed semi-quantitatively. Plasma samples were taken before the start of exercise (baseline), at maximum exercise and every hour up to 6 h after maximum exercise. RESULTS: Myocardial ischemia was present in 42 (33%) patients. MPO levels rapidly increased during exercise in patients with and without ischemia (to 131% (106-172%) and 145% (121-199%) of baseline, respectively). MPO levels and absolute changes in MPO did not differ between patients with and without ischemia at any time point. None of the patient characteristics, including presence of ischemia, was independently predictive of the absolute increase in MPO levels during exercise. CONCLUSIONS: Exercise related immediate increases in MPO levels do not reflect myocardial ischemia.

Stability of melatonin and temperature as circadian phase markers and their relation to sleep times in humans.

Circadian rhythms of core body temperature and melatonin are commonly used as phase markers of the circadian clock. Melatonin is a more stable marker of circadian phase when measured under constant routine conditions. However, little is known about the variability of these phase markers under less controlled conditions. Moreover, there is little consensus about the preferred method of analysis. The objective of this study was to assess various methods of calculating melatonin and temperature phase in subjects with regular sleep schedules living in their natural environment. Baseline data were analyzed from 42 healthy young subjects who were studied on at least two occasions. Each hospital admission was separated by at least 3 weeks. Subjects were instructed to maintain a regular sleep schedule, which was monitored for 1 week before admission by sleep logs and actigraphy. Subjects spent one habituation night under controlled conditions prior to collecting baseline temperature and melatonin measurements. The phase of the melatonin rhythm was assessed by 9 different methods. The temperature nadir (Tmin) was estimated using both Cleveland and Cosine curve fitting procedures, with and without demasking. Variability between admissions was assessed by correlation analysis and by the mean absolute difference in timing of the phase estimates. The relationship to sleep times was assessed by correlation of sleep onset or sleep offset with the various phase markers. Melatonin phase markers were more stable and more highly correlated with the timing of sleep than estimates of Tmin. Of the methods for estimating Tmin, simple cosine analysis was the least variable. In addition, sleep offset was more strongly correlated with the various phase markers than sleep onset. The relative measures of melatonin offset had the highest correlation coefficients, the lowest study-to-study variability, and were more strongly associated with sleep timing than melatonin onsets. Concordance of the methods of analysis suggests a tendency for the declining phase of the melatonin profile to be more stable and reliable than either markers of melatonin onset or measures of the termination of melatonin synthesis.

The circadian clock mutation alters sleep homeostasis in the mouse.

The onset and duration of sleep are thought to be primarily under the control of a homeostatic mechanism affected by previous periods of wake and sleep and a circadian timing mechanism that partitions wake and sleep into different portions of the day and night. The mouse Clock mutation induces pronounced changes in overall circadian organization. We sought to determine whether this genetic disruption of circadian timing would affect sleep homeostasis. The Clock mutation affected a number of sleep parameters during entrainment to a 12 hr light/dark (LD 12:12) cycle, when animals were free-running in constant darkness (DD), and during recovery from 6 hr of sleep deprivation in LD 12:12. In particular, in LD 12:12, heterozygous and homozygous Clock mutants slept, respectively, approximately 1 and approximately 2 hr less than wild-type mice, and they had 25 and 51% smaller increases in rapid eye movement (REM) sleep during 24 hr recovery, respectively, than wild-type mice. The effects of the mutation on sleep are not readily attributable to differential entrainment to LD 12:12 because the baseline sleep differences between genotypes were also present when animals were free-running in DD. These results indicate that genetic alterations of the circadian clock system and/or its regulatory genes are likely to have widespread effects on a variety of sleep and wake parameters, including the homeostatic regulation of sleep.

Effects of age on the circadian system.

While aging has been associated with changes in the period and amplitude of circadian rhythms, little is known about how aging influences the response of the circadian clock to environmental stimuli. In this paper, we report on recent studies designed to determine the effects of advanced age on the response of the circadian clock to both photic and nonphotic stimuli in old hamsters (e.g., over 16 mo of age). Among the most pronounced age-related changes in the circadian rhythm of locomotor activity are: (a) alterations in the phase-angle of entrainment to the light-dark cycle; (b) an increase in the magnitude of phase shifts induced by pulses of light presented at specific circadian times; and (c) a loss of responsiveness to the phase shifting or entraining effects of stimuli which induce an acute increase of activity. Depletion of brain monoamine levels in young animals can induce changes in the responsiveness of the circadian clock to environmental stimuli which are similar to those which occur spontaneously in old animals, suggesting that aging alters monoaminergic inputs to the clock. Some of the age-related changes in the response of the clock to an activity-inducing stimulus can be reversed by implanting old animals with fetal SCN tissue. Determining the physiological basis for age related changes in the responsiveness of the clock to both internal and external stimuli, and the mechanisms by which normal circadian function can be restored, should lead to new insight into the functioning of the circadian clock and may lead to new approaches for normalizing disturbed circadian rhythms.

Current understanding of the circadian clock and the clinical implications for neurological disorders.

The changes in behavior that occur on a 24-hour basis to match the 24-hour changes in the physical environment due to the rotation of the earth on its axis are a hallmark of life on the planet Earth. The nervous system of both lower and higher organisms has evolved over millions of years to meet the demands of the dramatic changes in the physical environment that occur in relation to the changes in the light-dark cycle, optimizing the survival and reproductive success of the organism. During the past 50 years, it has been clearly established that the 24-hour nature of life was not simply a response to the 24-hour changes in the physical environment imposed by celestial mechanics, but instead was due to an internal time-keeping system in the brain. Many neurological disorders are associated with abnormal 24-hour rhythms, including the sleep-wake cycle. The recent discovery of the molecular basis of the neural clock in animals offers neurologists new avenues for studying the pathophysiology of neurological disorders.

Familial advanced sleep phase syndrome.

BACKGROUND: The circadian rhythms of sleep propensity and melatonin secretion are regulated by a central circadian clock, the suprachiasmatic nucleus of the hypothalamus. The most common types of sleep disorders attributed to an alteration of the circadian clock system are the sleep/wake cycle phase disorders, such as delayed sleep phase syndrome and advanced sleep phase syndrome (ASPS). Advanced sleep phase syndrome is characterized by the complaint of persistent early evening sleep onset and early morning awakening. Although the complaint of awakening earlier than desired is relatively common, particularly in older adults, extreme advance of sleep phase is rare. OBJECTIVE: To phenotypically characterize a familial case of ASPS. METHODS: We identified a large family with ASPS; 32 members of this family gave informed consent to participate in this study. Measures of sleep onset and offset, dim light melatonin onset, the Horne-Ostberg morningness-eveningness questionnaire, and clinical interviews were used to characterize family members as affected or unaffected with ASPS. RESULTS: Affected members rated themselves as "morning types" and had a significant advance in the phase of sleep onset (P<.001) and offset (P =.006) times. The mean sleep onset was 2121 hours for the affected family members and 0025 hours for the unaffected family members. The mean sleep offset was 0507 hours for the affected members and 0828 hours for the unaffected members. (Times are given in military form.) In addition, the phase of the circadian rhythm of melatonin onset for the affected family members was on average 3-1/2 hours earlier than for the unaffected members. CONCLUSIONS: The ASPS trait segregates with an autosomal dominant mode of inheritance. The occurrence of familial ASPS indicates that human circadian rhythms, similar to those in animals, are under genetic regulation. Genetic analysis of familial sleep and circadian rhythm disorders is important for identifying a specific gene(s) responsible for the regulation of sleep and circadian rhythms in humans.

Interaction between substituted 1-[2-(diphenylmethoxy)ethyl] piperazines and dopamine receptors.

Substituted 1-[2-(diphenylmethoxy)ethyl]piperazines were tested for their affinity to specific [3H]dopamine binding sites in membrane preparations from the corpus striatum of the rat. In particular, 4-(3-phenyl-2-prop(en)yl)- and 4-(3-phenyl-2-butyl)-substitution yielded compounds potent in displacing [3H]dopamine from its binding sites, with IC50-values in the order of 10 nM. There was a significant correlation between the IC50-values determined in this binding assay and the IC50-values obtained for the same compounds in a previous study on their potency to inhibit the uptake of dopamine in synaptosomal preparations of the striatum of the rat. Current insight in structural requirements for binding to dopamine receptors, as obtained mainly with rigid analogues of dopamine, gives no satisfactory explanation for the dopaminergic activity of the piperazine derivatives tested.