Showing papers on "Morning published in 2001"

Association of intrinsic circadian period with morningness-eveningness, usual wake time, and circadian phase.

Abstract: The biological basis of preferences for morning or evening activity patterns ("early birds" and "night owls") has been hypothesized but has remained elusive. The authors reported that, compared with evening types, the circadian pacemaker of morning types was entrained to an earlier hour with respect to both clock time and wake time. The present study explores a chronobiological mechanism by which the biological clock of morning types may be set to an earlier hour. Intrinsic period, a fundamental property of the circadian system, was measured in a month-long inpatient study. A subset of participants also had their circadian phase assessed. Participants completed a morningness-eveningness questionnaire before study. Circadian period was correlated with morningness-eveningness, circadian phase, and wake time, demonstrating that a fundamental property of the circadian pacemaker is correlated with the behavioral trait of morningness-eveningness.

Diverse patterns of neuroendocrine activity in maltreated children.

Abstract: Cortisol regulation was investigated in a sample of school-aged maltreated (n = 175) and demographically comparable low-income nonmaltreated (n = 209) children in the context of a day camp research program. Overall group differences between maltreated and nonmaltreated children were not found for average morning or average afternoon cortisol levels. However, significant variations were found that were based on the subtypes of maltreatment that the children had experienced. Maltreated children who had been both physically and sexually abused (as well as neglected or emotionally maltreated) exhibited substantial elevations in morning cortisol levels; children who had high (>1 SD) cortisol levels in both the morning and afternoon were also overrepresented in the multiple abuse group. Developmental timing of maltreatment did not account for these group differences, whereas the severity of sexual abuse was implicated. In contrast to the multiple abuse group, a subgroup of physically abused children showed evidence of a trend toward lower morning cortisol relative to nonmaltreated children with a significantly smaller decrease in cortisol levels from morning to afternoon. The findings are discussed in terms of the diversity of atypical cortisol regulation patterns that are exhibited among maltreated children.

Circadian time of morning light administration and therapeutic response in winter depression.

Abstract: Background: We investigated a possible mechanism of action for the antidepressant response to light—phase advances of the circadian clock—by measuring the onset of melatonin secretion before and after light treatment in the morning or evening. Methods: Plasma melatonin was sampled in 42 patients with seasonal affective disorder, in the evening or overnight while depressed and after 10 to 14 days of light therapy (10000 lux for 30 minutes) when symptoms were reassessed. Results: Morning light produced phase advances of the melatonin rhythm, while evening light produced delays, the magnitude depending on the interval between melatonin onset and light exposure, or circadian time (morning, 7.5 to 11 hours; evening, 1.5 to 3 hours). Delays were larger the later the evening light (r=0.40), while advances were larger the earlier the morning light (r=0.50). Although depression ratings were similar with light at either time of day, response to morning light increased with the size of phase advances up to 2.7 hours (r=0.44) regardless of baseline phase position, while there was no such correlation for evening light. In an expanded sample (N=80) with the sleep midpoint used as a reference anchor for circadian time, early morning light exposure was superior to late morning and to evening exposure. Conclusion: The antidepressant effect of light is potentiated by early-morning administration in circadian time, optimally about 8.5 hours after melatonin onset or 2.5 hours after the sleep midpoint.

Transition from Dim to Bright Light in the Morning Induces an Immediate Elevation of Cortisol Levels

Abstract: The only well documented effect of light exposure on endocrine function is the suppression of nocturnal melatonin. Bright light exposure has behavioral effects, including the alleviation of sleepiness during nocturnal sleep deprivation. The present study examines the effects of bright light on the profiles of hormones known to be affected by sleep deprivation (TSH) or involved in behavioral activation (cortisol). Eight healthy men participated each in three studies involving 36 h of continuous wakefulness. In one study, the subjects were exposed to constant dim light (baseline). In the two other studies, dim light exposure was interrupted by a 3-h period of bright light exposure either from 0500-0800 h (early morning study) or from 1300-1600 h (afternoon study). Blood samples were obtained every 15 min for 24 h to determine melatonin, cortisol, and TSH concentrations. Alertness was estimated by the number of lapses on two computerized vigilance-sensitive performance tasks. The early morning transition from dim to bright light suppressed melatonin secretion, induced an immediate, greater than 50% elevation of cortisol levels, and limited the deterioration of alertness normally associated with overnight sleep deprivation. No effect was detected on TSH profiles. Afternoon exposure to bright light did not have any effect on either hormonal or behavioral parameters. The data unambiguously demonstrate an effect of light on the corticotropic axis that is dependent on time of day.

Diurnal Variations of Convective Activity and Rainfall in Tropical Asia

Abstract: The diurnal variations of convective activity and rainfall in tropical Asia are investigated using hourly equivalent black body temperature (TBB) data from the Japanese Geostationary Meteorological Satellite (GMS-5), and hourly (or 3-hourly) rainfall data from Bangladesh, Thailand, Vietnam and Malaysia. As an index of convective activity, we use the frequency of occurrence of the difference in TBB between the infrared-1 and the water vapor channel ΔTBB (= TBB(IR1) − TBB(WV)) of less than 3K. By using this index, the diurnal variations of convective activity and rainfall have approximately the same phase. The time when convective activity reaches its maximum and minimum is examined in the domain of 80-120°E and 0-30°N. As a result, it is found that the largest number of grids exhibits the maximum at 17LT (local time) and 14LT, and the minimum at 11LT and 21LT over land and sea, respectively. Moreover, without using the harmonic analysis, which is a conventional method of analyzing the diurnal variation, areas with the maximum during the late night-early morning hours are clearly separated from those with the afternoon-early evening maximum. This late night-early morning maximum is mostly found in the windward areas of mountains, in basins and valleys, and in coastal areas. Therefore, this kind of maximum is most likely associated with terrain or its induced local circulations such as mountain and land breezes. From the analysis of rainfall data, it is also shown that the late night-early morning maximum is found at stations with high rainfall. The number of stations with the late night-early morning maximum is less than that with the afternoon-early evening maximum. But, the mean daily rainfall at the former stations is on average a few times greater than that at the latter stations. Thus, the diurnal variation averaged for all stations in the four countries has two nearly equal maxima at 05LT and 16LT. This result suggests a strong possibility that the late night-early morning maxima of convective activity and rainfall have a great efffect on energy and water cycles in tropical Asia.

Preliminary results on mood state, salivary testosterone:cortisol ratio and team performance in a professional soccer team.

Abstract: Mood, as measured by the profile of mood states questionnaire (POMS), salivary cortisol (F) and testosterone (T) levels, and performance were examined in 17 male soccer players 4 times during a season. Soccer players provided three saliva samples when getting up (resting values, 8 a.m.), before breakfast (11.30 a.m.), and between 4.00p.m. and 6.00 p.m. The initial measures were performed 1 day following the start of season training (T1). They were then performed before and after a high-intensity training programme (T2 and T3, respectively) and 16 weeks after T3 (T4). Iceberg profiles of POMS were observed during T1, T2 and T3, which coincided with successful performance. Subsequent decreased performance between T3 and T4 coincided with a decrease in vigor and an increase in tension and depression. Indeed, when the normal nycthemeral rhythm for F was observed (i.e. a decrease from morning until evening at all times; T1–T4), there was seemingly a non-statistical elevation of F on the morning of T3, which only became statistically significant at 11.30 a.m. on T3. In spite of a post-high-intensity training programme (T3) increase in catabolism, the soccer players presented iceberg profiles together with a high percentage of winning. Our results could suggest that in team soccer, a decreased T:F ratio does not automatically lead to a decrease in team performance or a state of team overtraining. It appears that combined psychological and physiological changes during high-intensity training are primarily of interest when monitoring training stress in relation to performance.

The effect of evening alcohol consumption on next-morning glucose control in type 1 diabetes

Abstract: OBJECTIVE —Alcohol is associated with acute hypoglycemia in patients with type 1 diabetes. After drinking alcohol in the evening, delayed hypoglycemia has also been described, although its cause is unknown. We performed a controlled study to investigate this phenomenon. RESEARCH DESIGN AND METHODS —We admitted six men with type 1 diabetes (aged 19–51 years, HbA 1c 7.0–10.3%) on two occasions, from 5:00 p.m. to 12:00 noon the following day. They received regular insulin injections before standardized meals, at 6:00 p.m. and 8:00 a.m., and a basal insulin infusion (0.15 mU · kg −1 · min −1 ) from 11:00 p.m. They drank either dry white wine (0.75 g/kg alcohol) or mineral water at 9:00 p.m. over 90 min. Blood glucose, alcohol, insulin, cortisol, growth hormone, and glucagon levels were measured. RESULTS —Blood ethanol reached a mean (SEM) peak of 19.1 (1.2) mmol/l and was undetectable by 8:00 a.m. There were no significant differences in evening or overnight blood glucose levels between the studies. In the morning, fasting and postprandial blood glucose levels were significantly lower after consumption of wine (postprandial peak 8.9 [1.7] vs. 15 [1.5] mmol/l, P –1 · h –1 , P = 0.04). There were no differences in insulin or other hormone levels. CONCLUSIONS —In type 1 diabetes, moderate consumption of alcohol in the evening may predispose patients to hypoglycemia after breakfast the next morning. This is associated with reduced nocturnal growth hormone secretion. Patients should be informed of this risk and advised regarding appropriate preventative measures.

Resistance to glucocorticoid feedback in obesity.

Abstract: Increased hypothalamo-pituitary-adrenal axis drive has been reported in obese subjects but with paradoxically low or normal levels of plasma cortisol. Our current study was designed to investigate whether glucocorticoid feedback was altered in obesity, both under basal and stressed conditions. Plasma ACTH and cortisol concentrations in male control or obese subjects (age range 20-50 yr) were measured at frequent intervals over 24 h during infusion of saline or hydrocortisone at two physiological doses (7.5 and 15 mg/d) designed to occupy predominantly mineralocorticoid rather than glucocorticoid receptors. The same subjects then underwent insulin-induced hypoglycemia either in the morning or the evening. Obese subjects had significantly higher basal ACTH and lower cortisol concentrations throughout the 24 h infusion period, compared with controls (P < 0.05, two-way ANOVA followed by Newman-Keuls posthoc analysis). Basal plasma ACTH was decreased in obese groups given low- or high-dose hydrocortisone during the day (P < 0.05) but not during the night, unlike controls who responded to hydrocortisone both during the day and at night (P < 0.05). Obese subjects also showed resistance to steroid-induced inhibition of the ACTH response to hypoglycemia, compared with controls (P < 0.05). These data clearly show that obesity is associated with a relative insensitivity to glucocorticoid feedback, which is most marked during the night, and suggest that this condition is characterized by a decreased mineralocorticoid receptor response to circulating corticosteroids.

Age, gender and early morning highway accidents

Abstract: Accident register data, time budget studies and road traffic flow data were used to compute the age and gender-dependent relative risk [odds ratio (OR)] of being involved in a driving accident in which the driver was injured or killed Alcohol-related accidents were excluded from the analysis The results showed that the night-time risk, compared with that of the forenoon, was dramatically increased (OR=5) for young drivers (18--24 years) and reduced for old (65+) drivers In direct comparison, the young drivers had 5-10 times higher risk of being involved in an accident during late night than during the forenoon, with the excess risk during the daytime being considerably lower Women had a less pronounced night-time peak than men In direct comparison, men had twice as high a risk as women during the late night hours The results clearly demonstrate a strong effect of young age on night-time accident risk, together with a moderate effect of (male) gender

Paying Attention to Time as one Gets Older

Abstract: Age-related changes in attention and interval timing as a function of time of day were examined using a temporal bisection task with single and compound auditory and visual stimuli. Half of the participants in each age group were tested in the morning, and half were tested in the afternoon. Duration judgments were found to be shorter for visual signals than for auditory signals. This discrepancy was greater in the morning than in the afternoon and larger for the older than for the younger adults. Young adults showed equal sensitivity to signal duration for single and compound trials and higher sensitivity in the afternoon than in the morning for both signal modalities. In contrast, older adults showed impaired sensitivity on compound trials and the greatest sensitivity overall to single visual trials in the morning. These results suggest that age-related reductions in attentional resources may cause older adults to focus on signals that require controlled attention during specific phases of the circadian ...

Glucose facilitation of cognitive performance in healthy young adults: examination of the influence of fast-duration, time of day and pre-consumption plasma glucose levels.

Abstract: Rationale: Previous investigations have demonstrated increased performance after the administration of a glucose-load on certain aspects of cognitive functioning in healthy young adults. Generally these studies have used a procedure where participants were tested in the morning after an overnight fast. Objective: The aim of the present study was, for the first time, to investigate the glucose cognitive facilitation effect under more natural testing times and with shorter duration of the previous fast. Methods: Measures of verbal and non-verbal memory performance were compared under different fasting intervals (2-h fast versus overnight fast), times (morning versus afternoon) and glycaemic conditions (glucose versus aspartame drinks) in healthy young participants. Results: There was a significant glucose facilitation effect on long-term verbal memory performance. In addition, glucose significantly enhanced long-term spatial memory performance. The effect of glucose was essentially equivalent whether it was given after an overnight fast or a 2-h fast following breakfast or lunch. There was no effect of drink and time of day on working memory performance. Conclusions: The results of this study further support the hypothesis that glucose administration can enhance certain aspects of memory performance in healthy young adults. More significantly, the findings indicate that this cognitive facilitation effect persists under more naturalistic conditions of glucose administration and is not restricted to long fast durations or morning administration.

Cardiovascular risk and therapeutic intervention for the early morning surge in blood pressure and heart rate.

Abstract: The incidence of most adverse cardiovascular events appears to follow a circadian pattern, reaching a peak in the morning shortly after wakening and arising. The activities of many physiologic parameters, including hemodynamic, hematologic and humoral factors, also fluctuate in a cyclical manner over the 24h. It has been suggested that, during the post-awakening hours, the phases of these cycles synchronize to create an environment that predisposes to atherosclerotic plaque rupture and thrombosis in susceptible individuals, thereby accounting for the heightened cardiovascular risk at this time of day. Blood pressure and heart rate are part of this physiologic process, following a clear circadian rhythm characterized by a fall during sleep and a sharp rise upon awakening. This so-called 'morning surge' in blood pressure may act as a trigger for cardiovascular events, including myocardial infarction and stroke. The clinical implication of these observations is that antihypertensive therapy should provide blood pressure control over the entire interval between doses. For agents taken once daily in the morning, the time of trough plasma drug level (and lowest pharmacodynamic effect) will often coincide with the early morning surge in blood pressure and heart rate. For these reasons, chronotherapeutic formulations of drugs and intrinsically long-acting antihypertensive agents provide the most logical approach to the treatment of hypertensive patients since they provide 24 h blood pressure control from a single daily dose as well as attenuating the early morning rise in blood pressure (and in some instances heart rate).

Matching grass supply to grazing patterns for dairy cows

Abstract: Four groups of five spring-calving Holstein–Friesian cows were given a daily grass allowance in a strip-grazing system after either morning (AM; two groups) or afternoon (PM; two groups) milking over a 10-week period. The dry-matter (DM) concentration of the grass tended to be higher after afternoon milking [AM, 178 vs. PM, 197 g DM (s.e.d. 5·32) kg–1 fresh matter], and water-soluble carbohydrate concentrations were significantly higher [AM, 175 vs. PM, 204 g kg–1 DM (s.e.d. 6·67)]. Although the total times spent grazing (AM, 461 vs. PM, 462 min day–1) were similar for both groups, cows receiving their allocation in the afternoon had a longer evening meal (>4 h duration) compared with those receiving their allocation in the morning (2–3 h), which also spent more time ruminating [AM, 454 vs. PM, 433 min day–1 (s.e.d. 1·80)]. This short-term study demonstrated how a relatively simple change in management practice in strip-grazing systems could benefit milk yield and pasture utilization. This is because the DM and water-soluble carbohydrate contents of the herbage are higher in the evening than in the morning, and this is when grazing animals concentrate much of their daily grazing activity.

Treatment of asthma by the inhaled corticosteroid ciclesonide given either in the morning or evening.

Abstract: The study addressed the question whether the novel inhaled prodrug corticosteroid ciclesonide is equally effective when inhaled in the morning compared to the evening. For this purpose a double-blind, randomized, parallel group study was initiated in which 209 asthmatic patients (forced expiratory volume in one second = 50-90% predicted) inhaled either 200 microg ciclesonide in the morning or in the evening, for 8 weeks. Efficacy was assessed by means of spirometry as well as daily recordings of morning and evening peak expiratory flow (PEF), symptoms and use of rescue medication. The 24-h urinary cortisol excretion was measured to evaluate any effect on hypothalamic-pituitary-adrenol axis. Ciclesonide significantly improved asthma control. Morning and evening administration was shown to be equally effective for the different spirometry variables, evening PEF, symptoms, use of rescue medication and number of asthma exacerbations. Regarding morning PEF, the improvements after evening dosing were more prominent and equivalence of morning and evening administration could not be demonstrated. No relevant influence on cortisol excretion was found. Overall, the study indicates that ciclesonide can be given either in the morning or in the evening to meet the patients' preference and individual medical needs, although evening administration may lead to a more pronounced improvement in morning peak expiratory flow.

Effect of different mouthrinses on morning breath.

Abstract: Background: Morning breath odor is an often-encountered complaint. This double-blind, crossover, randomized study aimed to examine the bad breath-inhibiting effect of 3 commercially available mouthrinses on morning halitosis during an experimental period of 12 days without mechanical plaque control. Methods: Twelve medical students with a healthy periodontium refrained from all means of mechanical plaque control during 3 experimental periods of 12 days (with intervening washout periods of at least 3 weeks). A professional oral cleaning preceded each period. During each experimental period, as the only oral hygiene measure allowed, the students rinsed twice a day with one of the following formulations in a randomized order: CHX-Alc (a 0.2% chlorhexidine [CHX] solution); CHX-NaF (CHX 0.12% plus sodium fluoride 0.05%); or CHX-CPC-Zn (CHX 0.05% plus cetylpyridinium chloride 0.05% plus zinc lactate 0.14%). After 12 days, morning breath was scored via volatile sulfur compound (VSC) level measurements of the mou...

Hormone levels of world class cyclists during the Tour of Spain stage race

Abstract: Objectives—To evaluate the hormonal response to strenuous endurance exercise performed by elite athletes. Methods—Nine professional cyclists (mean (SD) age 28 (1) years; mean (SD) VO2MAX 75.3 (2.3) ml/kg/min) who participated in a three week tour race (Vuelta a Espana 1999) were selected as subjects. Morning urinary levels of 6-sulphatoxymelatonin (aMT6s) and morning serum levels of testosterone, follicle stimulating (FSH), luteinising hormone (LH), and cortisol were measured in each subject at t0 (before the competition), t1 (end of first week), t2 (end of second week), and t3 (end of third week). Urine samples of aMT6s were also evaluated in the evening at t0 ,t 1 ,t 2, and t3. Results—Mean urinary aMT6s levels had increased significantly (p<0.01) during the day after each stage (1091 (33) v 683 (68) ng/ml at t1; 955 (19) v 473 (53) ng/ml at t2; 647 (61) v 337 (47) ng/ml at t3). Both morning and evening aMT6s levels decreased significantly during the study. A similar pattern was observed for morning serum levels of cortisol and testosterone. Conclusions—The results suggest that the basal activity of the pineal gland, adrenal glands, and testis may be decreased after consecutive days of intense, long term exercise. (Br J Sports Med 2001;35:424‐430)

Altered circadian cortisol secretion in Alzheimer's disease: clinical and neuroradiological aspects.

Abstract: We determined circadian salivary cortisol levels in 18 outpatients affected by probable Alzheimer's disease (AD) and looked for a possible correlation with both cognitive impairment and brain CT scan findings. The diagnosis of probable AD was made according to the NINCDS-ADRDA criteria. The severity of cognitive impairment was quantified using the Mini Mental State Examination (MMSE) and the Global Deterioration Scale (GDS). Cortisol levels were measured on saliva samples collected at 08:00 AM and 08:00 PM. For each sample, a duplicate cortisol measurement was performed on 50 microl of saliva by means of a modified commercial radioimmunoassay kit. At the same time, 11 of the 18 AD patients enrolled also underwent a brain CT scan to estimate cerebral atrophy by using linear indexes. The mean value of cortisol levels was significantly higher in AD patients than in controls at both the morning and the evening measurements, and the circadian fluctuation of cortisol was less marked in AD patients than in controls, although this difference did not reach statistical significance. Morning cortisol levels were significantly correlated to both the MMSE and the GDS scores. A significant correlation was also found between morning cortisol levels and all the cerebral atrophy indexes. By contrast, no correlation was observed between evening cortisol levels or cortisol circadian fluctuations and either cognitive impairment or cerebral atrophy. In conclusion, despite the potential biases deriving from the small sample and the limitations of the CT scan study, our results suggest that, in AD patients, hypercortisolemia is correlated with severity of the disease.

Salivary cortisol levels and work-related stress among emergency department nurses.

Abstract: The objective of this study was to assess and compare the self-perceived work-related stress of emergency department (ED) and general ward (GW) nurses and to assess the relationship between self-perceived stress and salivary cortisol levels in these groups of nurses. Seventy-three female ED (n = 23) and GW (n = 50) nurses from a general hospital completed a self-administered questionnaire. A modified mental health professional stress scale (PSS) was used to measure self-perceived work-related stress. Salivary samples were collected at the start and end of morning shiftwork. An enzyme-linked immunosorbent assay method was used to determine the salivary cortisol concentration (nmol/L). ED nurses perceived that nursing was more stressful (mean, 1.58; 95% confidence interval [CI], 1.35 to 1.81) than did GW nurses (mean, 1.30; 95% CI, 1.18 to 1.40). On the PSS subscales, scores of organizational structure and process, lack of resources, and conflict with other professionals were higher in ED nurses (all P < 0.01). The morning cortisol was significantly lower in ED (geometric mean, 9.10; 95% CI, 6.62 to 12.42 nmol/L) than in GW (geometric mean, 15.45; 95% CI, 11.86 to 20.14 nmol/L) nurses. Log morning salivary cortisol was negatively correlated with PSS (r = -0.255), scores of organizational structure and process, and conflict with other professionals (all P < 0.05). The difference between morning and afternoon cortisol concentration in ED nurses (geometric mean, 6.35; 95% CI 4.14 to 9.93 nmol/L) was lower than in GW nurses (geometric mean, 12.42; 95% CI, 9.38 to 16.28 nmol/L). The log value of the difference correlated marginally with PSS (r = -0.21, P = 0.07) and significantly with scores of organizational structure and process, lack of resources, and conflict with other professionals (all P < 0.05). There was no difference between the two groups in afternoon salivary cortisol level. ED nurses perceived more stress compared with GW nurses. Morning salivary cortisol concentration is better correlated with PSS compared with the morning-afternoon salivary cortisol difference. The result raises the possibility of using a single morning salivary cortisol sample to reflect self-perceived stress.

Human Glucocorticoid Feedback Inhibition Is Reduced in Older Individuals: Evening Study

Abstract: We have previously shown that when tested in the morning, older men and women, pretreated with metyrapone to block endogenous cortisol synthesis, exhibit delayed suppression of plasma ACTH in response to cortisol infusion. To confirm this finding and to determine whether aging-related changes in feedback responsiveness are exaggerated near the time of the circadian nadir in adrenocortical secretion, we performed a similar study in the evening. Healthy young (20-35 yr, n = 22) and old (>65 yr, n = 21) men and women were administered metyrapone orally (750 mg) at 1600 and 1900 h, followed by a cortisol infusion of 0.06 mg/kg/h for 150 min. Blood samples were taken at 15-min intervals for 4 h following infusion onset for measurement of plasma ACTH, cortisol, 11-deoxycortisol, and corticosteroid binding globulin. When corrections were made for differences in circulating cortisol concentrations achieved among age and gender subgroups, feedback inhibition of ACTH was found to be significantly greater in young than in old subjects of both genders. Our studies support the hypothesis that glucocorticoid responses to stress in aging individuals are likely to be prolonged due to blunted and delayed inhibition of ACTH secretion, thus increasing the total exposure to glucocorticoids.

Innovative working schedule: introducing one short nap during the night shift

Abstract: In order to test the possible long-term effects of the implementation of a short nap during night shifts, an experiment was conducted over a period of 1 year with 12 volunteer shiftworkers operating in an industrial plant. They were authorized, under certain conditions, to use individual sleeping areas, for a maximum of 1 hour, between 23h30 and 3h30. The participants were asked to fill in a short questionnaire every day during the entire study. The questions concerned the schedule of the main sleep period, the afternoon nap and the night-time nap, if any, as well as the evaluation of mood and the quality of work. This daily questionnaire was supplemented by an extensive questionnaire applied every 2 months in order to assess the main changes introduced in the life of the participants by this new working schedule. Results showed that this new organization introduced a general satisfaction about the quality and the easiness of the work at night. The vigilance level was considered to be higher during the hours following the nap. The efficacy of the nap time progressively increased for most subjects. The general quality of life improved for most subjects. While a few of them considered that falling asleep was less easy on the following morning at home, the statistical analysis did not show any detrimental effect of the short rest period on the length of the immediately consecutive main sleep period. However, different statistical analyses allow us to reveal significant differences between the main sleep durations following the night shift compared with those following both the afternoon shift and the resting period. The main sleep duration following the night shift was not statistically different from that of the morning shift. These results are very encouraging. A short nap during the night shift can be considered as a positive way to counteract the low level of vigilance that normally occurs during the late part of the night.

Sub‐optimal morning temperature induces photoinhibition in dense outdoor cultures of the alga Monodus subterraneus (Eustigmatophyta)

Abstract: Diel changes in photosynthetic oxygen evolution and several photochemical parameters measured by chlorophyll fluorescence quenching and induction were measured in outdoor dense cultures of the alga Monodus subterraneus (Eustigmatophyta). Cultures were maintained under two temperature regimes. In one, a rise in temperature was initiated in the morning by the increase in solar radiation up to the optimal temperature of 28 °C; in the other, a heating device was used to increase the rate of warming up in early morning. Although the two cultures were maintained at the same temperature and light intensity for most of the day, cultures exposed for only a short time to suboptimal morning temperature showed a larger decrease in almost all the photosynthetic parameters. By comparing the diel changes in maximal photochemistry efficiency of photosystem II, the electron transport rate and the photochemical and non-photochemical chlorophyll fluorescence quenching of the cultures, we concluded that even a relatively short exposure to suboptimal morning temperatures induced photoinhibitory damage. The higher photochemical activity of the heated culture was also reflected in a significant increase in productivity, which was 60% higher in the morning heated cultures than in the non-heated cultures.

Compared with nibbling, neither gorging nor a morning fast affect short-term energy balance in obese patients in a chamber calorimeter

Abstract: OBJECTIVE: To test if a diet of 4.2 MJ/24 h as six isocaloric meals would result in a lower subsequent energy intake, or greater energy output than (a) 4.2 MJ/24 h as two isocaloric meals or (b) a morning fast followed by free access to food. DESIGN: Subjects were confined to the Metabolic Unit from 19:00 h on day 1 to 09:30 h on day 6. Each day they had a fixed diet providing 4.2 MJ with three pairs of meal patterns which were offered in random sequence. They were: six meals vs two meals without access to additional foods (6vs2), or six meals vs 2 meals with access to additional food (6+vs2+), or six meals vs four meals (6+vsAMFAST). In the AMFAST condition the first two meals of the day were omitted to reduce daily intake to 2.8 MJ and to create a morning fast, but additional food was accessible thereafter. Patients were confined in the chamber calorimeter from 19:00 h on day 2 until 09:00 h on day 4, and then from 19:00 h on day 4 to 09:00 h on day 6. The order in which each meal pattern was offered was balanced over time. MEASUREMENTS: Energy expenditure (chamber calorimetry), spontaneous activity (video) and energy intake (where additional foods were available) during the final 24 h of each dietary component. SUBJECTS: Ten (6vs2), eight (6+vs2+) and eight (6+vsAMFAST) women were recruited who had a BMI of greater than 25 kg/m2. RESULTS: From experiment 6vs2 the difference between energy expenditure with six meals (10.00 MJ) and two meals (9.96 MJ) was not significant (P=0.88). Energy expenditure between 23:00 h and 08:00 h (‘night’) was, however, significantly higher (P=0.02) with two meals (9.12 MJ/24 h) compared with six meals (8.34 MJ/24 h). The pattern of spontaneous physical activity did not differ significantly between these two meal patterns (P>0.05). Total energy intake was affected by neither meal frequency in experiment 6+vs2+ (10.75 MJ with six, 11.08 MJ with two; P=0.58) nor a morning fast in experiment 6+vsAMFAST (8.55 MJ/24 h with six, 7.60 MJ with AMFAST; P=0.40). The total diet of subjects who had a morning fast tended to have a lower percentage of total energy from carbohydrate (40%) than when they had six meals per 24 h (49%) (P=0.05). Subsequent energy balance was affected by neither meal frequency (6vs2; P=0.88, 6+vs2+; P=0.50) nor a morning fast (P=0.18). CONCLUSIONS: In the short term, meal frequency and a period of fasting have no major impact on energy intake or expenditure but energy expenditure is delayed with a lower meal frequency compared with a higher meal frequency. This might be attributed to the thermogenic effect of food continuing into the night when a later, larger meal is given. A morning fast resulted in a diet which tended to have a lower percentage of energy from carbohydrate than with no fast. International Journal of Obesity (2001) 25, 519–528

Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure.

Abstract: Objective: Bright light therapy in seasonal affective disorder (SAD) has been studied extensively. However, little attention has been given to subsyndromal seasonal affective disorder (SSAD) or the use of bright light in the workplace. Many patients using bright light boxes complain of the inconvenience of use. Much of this inconvenience involves the often-recommended early timing of the bright light therapy. Patients, who already have difficulty awakening, often have difficulty using the bright light therapy soon after awakening before going to work. If bright light could be used effectively in the workplace, the treatment would be more convenient; the improved convenience would probably improve compliance. In this study, we studied the effectiveness of bright light therapy in subjects with SSAD in the workplace, comparing morning bright light with afternoon bright light. Method: Morning and afternoon bright light treatment (2500 lux) were compared in 30 subsyndromal seasonal affective disorder patients using the bright light therapy in the workplace. Hamilton Depression Ratings and subjective measures of mood, energy, alertness and productivity were assessed before and after 2 weeks of light therapy. Results: Both morning and evening bright light significantly decreased the depression ratings and improved the subjective mood, energy, alertness and productivity scores. However, there were no significant differences between the two times of administration of the bright light treatment. Both bright light treatments were well tolerated. Conclusion: Bright light given in the workplace improves subjective ratings of mood, energy, alertness and productivity in SSAD subjects. Morning and afternoon bright lights resulted in similar levels of improvement.

Effect of morning exercise on counterregulatory responses to subsequent, afternoon exercise

Abstract: The aim of this study was to determine whether a bout of morning exercise (EXE1) can alter neuroendocrine and metabolic responses to subsequent afternoon exercise (EXE2) and whether these changes f...