Reduced urinary aldosterone excretion rates with normal plasma concentrations of aldosterone in the very elderly

Although aldosterone production declines with age, so does the aldosterone metabolic clearance rate (MCR), and the net effect of age on the circulating level of aldosterone may be less than can be predicted from production rates alone. The effect of age on aldosterone production and plasma levels was studied in a group of elderly individuals at a very advanced age when susceptibility to the impacts of age might be particularly pronounced. Seventeen nursing home patients, ages 75-99 (mean age 86 years), had aldosterone production assessed from the urinary excretion rate of the acid hydrolyzable 18-glucuronide conjugate of aldosterone. Aldosterone excretion was low in the elderly when compared to a group of healthy, young to middle-aged subjects: 123 +/- 19 (SEM) vs. 234 +/- 18 ng/h (P less than 0.001). However, plasma aldosterone concentrations in the elderly were well within a range observed in much younger and fully ambulatory subjects: 14.1 +/- 1.3 in the elderly vs. 15.9 +/- 1.8 ng/dL in the young. The plasma aldosterone concentration was apparently maintained at a normal level by a coincident decrease in both the metabolic clearance rate and the aldosterone production rate. In conclusion, an aldosterone deficiency state resulting from an age-correlated reduction in aldosterone production is probably uncommon in the elderly.     

Physiological effects of shift work on hospital nurses

OBJECTIVE: The purpose of this study was to assess the physiological effects of shift work on the urinary excretion rates of norepinephrine, 6-sulfatoxymelatonin and estriol in hospital nurses. METHOD: Twenty-four hour urine specimens were examined on a daytime/nighttime basis for each work shift of pregnant and non-pregnant subjects. The urinary norepinephrine and 6-sulfatoxymelatonin were measured by enzyme-linked immunosorbent assay and estriol by radio-immunoassay. RESULTS: Urinary norepinephrine level during the night work was higher than the night levels of the days off and the day shift. Urinary 6-sulfatoxymelatonin level during the night work was lower than the night levels of the days off and the day shift. Urinary estriol level of pregnant subjects showed no differences among work shift and also between daytime and nighttime. CONCLUSIONS: Urinary excretion rates of norepinephrine and 6-sulfatoxymelatonin were affected by shift work both for non-pregnant and pregnant subjects. It was unlikely that urinary estriol levels in the pregnant subjects were significantly affected by shift work.     

Urinary growth hormone excretion in 657 healthy children and adults: normal values, inter- and intraindividual variations.

Urinary growth hormone (u-GH) excretion was measured in 547 healthy children and 110 adults by ELISA with a detection limit of 1.1 ng/l u-GH after prior concentration of the urine samples (20- to 30-fold). u-GH excretion values were significantly dependent on the pubertal stage (p less than 0.0001) with maximum values in Tanner stage 3 for girls and 4 for boys. This corresponded to a peak in u-GH excretion between 11.5-14.5 years in girls and 12.5-16 years in boys. Additionally, u-GH excretion in adults was significantly higher than in prepubertal children (p less than 0.001). The day/night ratio of u-GH excretion (pg/h) was significantly higher in females than in males (p less than 0.01). In Tanner stages 1-4, u-GH excretion during the day was lower than that at night, whereas the opposite was true in late puberty and in adult women. The interindividual variation of u-GH excretion within the same Tanner stage was considerable and approximately double the intraindividual variation. The day-to-day variation could be further reduced by collection of three consecutive urine samples. The variations were larger if night samples instead of 24-hour samples were considered. The expression of u-GH excretion in nanograms per gram creatinine did not diminish the observed variation and blunted the pubertal increase in u-GH excretion. In conclusion, (1) u-GH excretion depends significantly on age, sex and pubertal maturation as does the day/night ratio of u-GH excretion. (2) The interindividual variation in u-GH excretion is considerable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiorenal-endocrine responses to head-out immersion at night

Cardiorenal-endocrine responses to 3-h head-out immersion (HOI) (water temperature = 34.5 +/- 0.5 degrees C) were studied during day (0900-1400 h) and night (2300-0400 h) in six hydropenic male human subjects. Although HOI induced a reversible increase in urine flow in all subjects, the response was faster and greater in magnitude during the day compared with night (P less than 0.05). Na excretion and osmolal clearance (Cosm) also followed the identical response pattern as urine flow, and in fact, the HOI-induced diuresis was entirely accounted for by the increased Cosm. Endogenous creatinine clearance was not different between the day and the night and remained unchanged during HOI. Both plasma renin activity and aldosterone concentration and urinary aldosterone excretion were nearly twofold greater during the day compared with night before HOI but decreased to the same level during HOI in both daytime and the nighttime series (P less than 0.05). There was no correlation between the Na excretion rate and renin-aldosterone levels either before or during HOI. Plasma antidiuretic hormone (ADH) level was comparable between day and night before HOI and decreased to a similar level during HOI in both daytime and nighttime series (P less than 0.05 for nighttime HOI). Cardiac output increased from 3.3 1/min before HOI to 5-6 1/min during HOI without showing any significant circadian difference. Hematocrit, hemoglobin, and plasma concentrations remained unchanged under all conditions. It is concluded that the renal response to HOI is subject to nocturnal inhibition, which cannot be attributed to circadian differences in the degree of HOI-induced central blood pooling, renin-aldosterone, or ADH responses.     

Hypothalamus-hypophysis-thyroid axis function in healthy aging

There is an increased frequency of dysthyroidism in elderly people. We investigated whether there are differences among healthy young middle-aged and elderly people in the 24 hour secretory profiles of TRH, TSH and free thyroxine. The study was carried out on fifteen healthy young, middle-aged subjects (range 36-55 years, mean age±s.e. 44.1±1.7) and fifteen healthy elderly subjects (range 67-79 years, mean age±s.e. 68.5±1.2). TRH, TSH and free thyroxine serum levels were measured in blood samples collected every four hours for 24 hours. The area under the curve (AUC), the mean of 06:00h-10:00h-14:00h and the mean of 18:00h-22:00h-02:00h hormone serum levels and the presence of circadian rhythmicity were evaluated. A normal circadian rhythmicity was recognizable for TRH and TSH in young, middle-aged subjects and for TSH in elderly subjects. Elderly subjects presented lower TSH levels, whereas there was no statistically significant difference in TRH and free thyroxine serum levels between young, middle-aged and elderly subjects. Aging is associated with an altered TSH secretion.     

Influence of oral dehydroepiandrosterone (DHEA) on urinary steroid metabolites in males and females

Oral dehydroepiandrosterone (DHEA) replacement therapy may have a multitude of potential beneficial effects and exerts its action mainly via peripheral bioconversion to androgens (and estrogens). A daily dose of 50-mg DHEA has been shown by us and others to restore low endogenous serum DHEA concentrations to normal youthful levels followed by an increase in circulating androgens and estrogens. As the hepatic first-pass effect may lead to a non physiological metabolism of DHEA after oral ingestion we studied the influence of two single DHEA doses (50 and 100 mg) on the excretion of steroid metabolites in 14 elderly males [age 58.8+/-5.1 years (mean +/- SEM)] with endogenous DHEAS levels <1500 ng/ml and in 9 healthy females (age 23.3+/-4.1 years) with transient suppression of endogenous DHEA secretion induced by dexamethasone (dex) pretreatment (4x0.5 mg/day/4 days). Urinary steroid profiles in the elderly males were compared to the steroid patterns found in 15 healthy young men (age 28.9+/-5.1 years). In the females the results were compared to their individual baseline excretion without dex pretreatment. Urinary steroid determinations were carried out by semiautomatic capillary gas-liquid chromatography. In both genders DHEA administration induced significant increases in urinary DHEA (females: baseline vs. 50 mg vs. 100 mg: 361+/-131 vs. 510+/-264 vs. 1541+/-587 microg/day; males: placebo vs. 50 mg vs. 100 mg: 434+/-154 vs. 1174+/-309 vs. 4751+/-1059 microg/day) as well as in the major DHEA metabolites androsterone (A) and etiocholanolone (Et). Fifty mg DHEA led to an excretion of DHEA and its metabolites only slightly above baseline levels found in young females and in young men, respectively, whereas 100 mg induced clearly supraphysiological values. After 50 mg DHEA the ratios of urinary DHEA metabolites (A/DHEA, Et/DHEA) were not significantly different between elderly males vs. young male volunteers and young healthy females versus their individual baseline levels. In conclusion, an oral dose of 30 to 50 mg DHEA restores a physiological urinary steroid profile in subjects with DHEA deficiency without evidence for a relevant hepatic first-pass effect on urinary metabolites.     

Bone resorption is induced on the second day of bed rest: results of a controlled crossover trial.

The aim of the study was to analyze the kinetics of short-term changes in bone turnover. We studied in a randomized crossover design the effects of 6 days of bed rest on eight healthy male subjects (mean body wt: 70.1 +/- 5.7 kg; mean age: 25.5 +/- 2.9 yr). The metabolic ward period was divided into three parts: 4 ambulatory days, 6 days of either bed rest or non-bed rest periods, and 1 recovery day. The diet was identical in both bed rest and non-bed rest phases. Continuous urine collection started on the first day in the metabolic ward to analyze excretion of bone resorption markers, namely C-telopeptide (CTX) and N-telopeptide (NTX), creatinine, urea, and 3-methylhistidine. On the second ambulatory day and on the fifth day of bed rest or during the non-bed rest phase, blood was drawn to analyze bone formation markers and amino acid concentrations. Urinary calcium excretion was increased as early as the first day of bed rest (P < 0.01). CTX and NTX excretion stayed unchanged during the first 24 h of bed rest compared with the non-bed rest period. However, already on the second day, both resorption markers had increased significantly. NTX excretion increased by 28.7 +/- 14.0% (P < 0.01), whereas CTX excretion rose by 17.8 +/- 8.3% (P < 0.001). Creatinine, urea, and 3-methylhistidine excretion did not change. We conclude that 24 h of bed rest are sufficient to induce a significant rise in osteoclast activity in healthy subjects.     

Alteration of circadian rhythmicity of CD3+CD4+ lymphocyte subpopulation in healthy aging

The CD4+ T helper/inducer and the CD8+ T suppressor/cytotoxic are major lymphocyte subsets that play a key role in cell-mediated immunity. Aging-related changes of immune function have been demonstrated. The purpose of this study is to analyze the dynamics of variation of these specific lymphocyte subsets in the elderly. In our study cortisol and melatonin serum levels were measured and lymphocyte subpopulation analyses were performed on blood samples collected every four hours for 24 hours from fifteen healthy young middle-aged subjects (age range 36-55 years) and fifteen healthy elderly male subjects (age range 67-79 years). A clear circadian rhythm was validated for the time-qualified changes of CD3+ and CD4+ cells with acrophase at night and for the time-qualified changes of CD8+ cells with acrophase at noon in young middle-aged subjects and for the time-qualified changes of CD3+ cells with acrophase at night and for the time-qualified changes of CD8+ cells with acrophase at noon in elderly subjects. No clear circadian rhythm was validated for the time-qualified changes of CD4+ cells in elderly subjects. No statistically significant correlation among lymphocyte subsets was found in elderly subjects. In elderly subjects CD3+ lymphocyte percentage was higher in the photoperiod and in the scotoperiod and cortisol serum level were higher in the scotoperiod in respect to young middle-aged subjects. In the elderly there is an alteration of circadian rhythmicity of T helper/inducer lymphocytes and this phenomenon might contribute to the aging-related changes of immune responses.     

Nocturnal polyuria and saluresis in renal allograft recipients.

The evolution of nocturnal polyuria and saluresis in renal allograft recipients was studied by comparing the day to night (D:N) ratios of urine volume and sodium excretion in 15 patients who had undergone transplantation less than one year previously (recent-transplant group) with those in 11 patients who had undergone transplantation at least one year previously. Eleven patients with chronic renal failure and 12 normal subjects served as controls. Patients in the recent-transplant group had significantly lower D:N ratios of urine volume and sodium excretion than the patients who had undergone transplantation at least a year before, while the ratios in this last group did not differ significantly from those in the normal subjects. Nocturnal polyuria and saluresis gradually subsided in five patients studied for three months. Chronic renal failure and uraemic autonomic neuropathy were unlikely causes of the nocturia. The patients in the recent-transplant group had significantly lower D:N ratios of urine volume than the controls with chronic renal failure, and the mean Valsalva ratio in eight of them was not significantly different from that in the normal subjects. An undue sensitivity of renal allografts to postural influences was proposed.     

Influence of lithium on biliary electrolyte and bile acid excretion in young and adult rats

The influence of a three-day lithium treatment on the biliary electrolyte and bile acid output was determined in 20- and 105-day-old rats. The osmolarity of bile and the biliary concentrations of cations (Na+, K+, Ca++, H+) and chloride were higher in untreated young rats than in adults, although bile flow and bile acid excretion rates of the young and adult animals were comparable. Lithium increased the biliary excretion of sodium, potassium and calcium and decreased the excretion of chloride and bicarbonate ions in both age groups. In contrast, lithium treatment reduced bile acid excretion only in adult rats. The lithium-induced alterations in biliary ion elimination may be caused by an intracellular replacement of sodium and/or potassium. These results indicate that after lithium treatment cation loss occurs in the young as well as in the adult organism not only via urine and faeces but also via bile.     

Urinary platelet-activating factor excretion is elevated in non-insulin dependent diabetes mellitus.

Proteinuria is currently considered a very sensitive predictor of diabetic nephropathy, but 20-25% of all diabetic patients with negative Albustix reaction excrete higher than normal (< 20 mg/24 h) amounts of albumin in their urine. It is our hypothesis that platelet-activating factor (PAF), a potent glycerophospholipid that acts as a chemical mediator for a wide spectrum of biological activities, including increased vascular permeability, may be produced in significant amounts during periods preceding microalbuminuria. In this study, we compared urinary PAF excretion in Mexican-American subjects who were diagnosed with non-insulin dependent diabetes mellitus (NIDDM) with their healthy control counterparts. The age of the NIDDM subjects (45.9 +/- 2.1 years) was not significantly different from the healthy control group, which was 39.4 +/- 2.7 years (P < 0.0672). The NIDDM subjects (body mass index, 29.9 +/- 1.1 compared to 26.1 +/- 0.9 kg/m2 in healthy controls) were characterized by significantly increased (P < 0.05) fasting plasma glucose (192 +/- 11 vs. 97 +/- 4 mg/dl in healthy controls), fasting insulin (20.9 +/- 2.4 vs. 12.3 +/- 1.6 microU/ml), fasting C-peptide (2.93 +/- 1.26 vs. 1.48 +/- 0.51 ng/ml), and hemoglobin A1c (10.3 +/- 0.7 vs. 5.6 +/- 0.3%), respectively. The urine output for the NIDDM and control subjects were 1942 +/- 191 ml/24 h and 1032 +/- 94 ml/24 h, respectively, and urinary albumin excretion (UAE) rates were estimated to be 38 +/- 7 micrograms/min and 11 +/- 1 micrograms/min, respectively. The NIDDM subjects produced significantly increased levels of urinary PAF (2606.3 +/- 513.1 ng/24 h compared with 77.9 +/- 14.1 ng/24 h in controls (or 1706.3 +/- 420.8 ng/ml compared with 85.4 +/- 17.8 pg/ml of urine, in NIDDM and control subjects, respectively). We found that urinary PAF excretion was significantly correlated with microalbumin excretion (r = 0.7) especially at UAE rates greater than 30 mg/day and more importantly, some NIDDM patients with negative Albustix reaction (i.e. normal UAE) produced significantly more PAF, suggesting that PAF excretion may precede microalbuminuria and that subtle injury to the kidneys are present in NIDDM long before overt albuminuria ensues, urinary PAF measurements could potentially therefore serve as a sensitive indicator of renal injury in diabetes mellitus. These results lend further credence to our hypothesis that PAF may be the biochemical compound linking the various members of the insulin resistance syndrome.     

Ventilatory and arousal patterns during sleep in normal young and elderly subjects

Since elderly subjects have lower chemosensitivity, we postulated that ventilation might be more state dependent in the elderly. To address this we investigated the changes in ventilation, measured by respiratory inductive plethysmography, with sleep in 12 healthy young (19-29 yr) and 13 elderly (greater than 65 yr) subjects. Ventilation was measured in representative periods in each sleep state. These data showed that there is no difference between the elderly and the young either in mean ventilation or in the variability of ventilation awake or in the different states of sleep. In both groups ventilation was variable in stage 1-2 sleep and least variable in stage 3-4 sleep. The variability in stage 1-2 sleep was due to periodic breathing (cycle time approximately 45 s) in both age groups. Although within a sleep state no differences were observed, over the night of study the elderly behaved differently from the young. Apneas occurred more frequently in the elderly, and 5 of 13 elderly met the criteria for sleep apnea syndrome compared with 1 of 12 young subjects. Apneas tended to occur predominantly in stage 1-2 sleep and seem to be an exaggeration of the periodicity that is typical of this state. Four of the elderly with apnea remained in this stage of sleep throughout the night of study. The apneic episodes usually terminated with an electroencephalogram arousal that occurred prior to or simultaneously with the onset of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of "no added salt diet" on blood pressure control and 24 hour urinary sodium excretion in mild to moderate hypertension

Background

The incidence of Hypertension as a major cardiovascular threat is increasing. The best known diet for hypertensives is 'no added salt diet'. In this study we evaluated the effect of 'no added salt diet' on a hypertensive population with high dietary sodium intake by measuring 24 hour urinary sodium excretion.

Methods

In this single center randomized study 80 patients (60 cases and 20 controls) not on any drug therapy for hypertension with mild to moderate hypertension were enrolled. 24 hour holter monitoring of BP and 24 hour urinary sodium excretion were measured before and after 6 weeks of 'no added salt diet'.

Results

There was no statistically significant difference between age, weight, sex, Hyperlipidemia, family history of hypertension, mean systolic and diastolic BP during the day and at night and mean urinary sodium excretion in 24 hour urine of case and control groups. Seventy eight percent of all patients had moderate to high salt intake. After 6 week of 'no added salt diet' systolic and diastolic BP significantly decreased during the day (mean decrease: 12.1/6.8 mmhg) and at night (mean decrease: 11.1/5.9 mmhg) which is statistically significant in comparison to control group (P 0.001 and 0.01). Urinary sodium excretion of 24 hour urine decreased by 37.1 meq/d ± 39,67 mg/dl in case group which is statistically significant in comparison to control group (p: 0.001). Only 36% of the patients, after no added salt diet, reached the pretreatment goal of 24 hour urinary sodium excretion of below 100 meq/dl (P:0.001).

Conclusion

Despite modest effect on dietary sodium restriction, no added salt diet significantly decreased systolic and diastolic BP and so it should be advised to every hypertensive patient.

Trial Registration

Clinicaltrial.govnumber NCT00491881     

Phase-shifts of apparent circadian rhythms due to west and east transmeridian flights or to corresponding night-shift sleep displacements

Phase movements of apparent circadian rhythms during 2 wk of forward or backward displacement of the sleep-wake cycle were investigated in four experimental series in a subject. The 7-hr delay or advance of sleep due to a westward or an eastward transmeridian flight was duplicated by corresponding sleep displacements during experimental night shifts. Sudden phase advances (or delays) by several hours were observed in the rhythms of continuously recorded rectal temperature and urinary excretion rates (4-hr collection intervals) of adrenaline, noradrenaline and aldosterone the first day after sleep-wake displacement. The desired 7-hr phase-shifts were reached more quickly and completely when the phase was delayed than when it was advanced. In addition, the best-fitting period of these rhythms became shorter than 24 hr when the phase was delayed, and longer than 24 hr when it was advanced. The apparent rhythms of urine flow and electrolyte excretions (potassium, sodium, zinc) were much weaker and their phase movements more irregular than those of hormonal excretion. It is concluded that the sudden phase-shifts resulted from the immediate adaptation of the exogenous components of the rhythms to the demands of the displaced sleep-wake patterns (masking effects) and that the true phase-shifts of the endogenous components followed more slowly and gradually.     

Phase-Shifts of Apparent Orcadian Rhythms Due to West and East Transmeridian Flights or to Corresponding Night-Shift Sleep Displacements

Phase movements of apparent circadian rhythms during 2 wk of forward or backward displacement of the sleep-wake cycle were investigated in four experimental series in a subject. The 7-hr delay or advance of sleep due to a westward or an eastward transmeridian flight was duplicated by corresponding sleep displacements during experimental night shifts. Sudden phase advances (or delays) by several hours were observed in the rhythms of continuously recorded rectal temperature and urinary excretion rates (4-hr collection intervals) of adrenaline, noradrenaline and aldosterone the first day after sleep-wake displacement. The desired 7-hr phase-shifts were reached more quickly and completely when the phase was delayed than when it was advanced. In addition, the best-fitting period of these rhythms became shorter than 24 hr when the phase was delayed, and longer than 24 hr when it was advanced. The apparent rhythms of urine flow and electrolyte excretions (potassium, sodium, zinc) were much weaker and their phase movements more irregular than those of hormonal excretion. It is concluded that the sudden phase-shifts resulted from the immediate adaptation of the exogenous components of the rhythms to the demands of the displaced sleep-wake patterns (masking effects) and that the true phase-shifts of the endogenous components followed more slowly and gradually.     

Aging, regularity and variability in maximum isometric moments

This study examined the variability and regularity of maximum isometric moment production of the plantar flexors in young and old subjects. It was hypothesized that in the development of maximum isometric moments there would be greater regularity in the moment profiles for older subjects compared with young subjects, due to the reduced number of motor units present in elderly muscle. Two groups of subjects produced three maximal isometric plantar flexions (young: n=11, mean age 23.8+/-2.8 years, mean mass 81.2+/-10.4 kg, mean height 1.78+/-0.05 m; elderly: n=13, mean age 74.0+/-3.3 years, mean mass 78.5+/-3.4 kg, mean height 1.73+/-0.05 m). The plateau of the moment-time curve was analyzed for each trial. A repeat measures analysis of variance showed the young subjects produced statistically greater peak plantar flexion moments than the elderly subjects, but similar coefficients of variation. Signal regularity was determined by computing the signal's approximate entropy, which demonstrated that the older group had greater regularity in their generation of moment profiles. The hypothesis was accepted, with a potential explanation for this increased regularity in old age being the reduced number of motor units to coordinate.     

Influence of age on orthostatic changes in plasma renin activity and urinary catecholamines in man.

The authors studied plasma renin activity (PRA), urinary epinephrine, norepinephrine and dopamine excretion and their mutual relationships in 54 healthy subjects under basal (recumbent) conditions and age-related orthostatic changes in these parameters. The test subjects were divided into six 10-years groups, according to their year of birth (1901-1910 to 1951-1960). In the oldest groups (1901-1910 and 1911-1920), both basal PRA values and norephrine and epinephrine excretion and their postural increase were smaller than in younger subjects. Conversely, urinary dopamine excretion and the dopamine/norepinephrine and epinephrine ratio rose with advancing age. There were no significant differences between the plasma sodium and potassium concentrations in the various groups. Urinary aldosterone excretion was slightly higher in the oldest group than in the others, but was still within the control value limits. The intravenous administration of Inderal reduced both resting PRA values and the orthostatic increase in the youngest age groups, so that their PRA approached the values in older subjects. Higher norepinephrine and epinephrine excretion and the lower dopamine/norepinephrine and epinephrine in young subjects may play a role in their higher PRA, especially in the orthostatic reaction. Diminution of sympathetic activity, with lower norepinephrine and epinephrine excretion and relatively high dopamine excretion, may have a direct bearing on the lower PRA values in older subjects. The diminished capacity of older subjects for catecholamine mobilization and raised renin secretion during an orthostatis stress may be related to the higher incidence of orthostatic forms of hypotension in old age.     

The Relationship between Sleep and Shift System, Age and Chronotype in Shift Workers

The purpose of this study was to investigate the effects of shift system, age, and chronotype on the sleep habits, sleepiness and catnaps of shift workers during night work. We administrated a Morningness-Eveningness Questionnaire and Life Habits Inventory to 561 male shift workers of three different shift systems in Korea. The mean scores on the Morningness-Eveningness Questionnaire clearly shifted toward the Morning type from the young to old groups. The waking and bedtimes during the day and evening shift were earlier for the older than for the younger groups, and these times were earlier across the Evening, Intermediate, to Morning type as well. Sleep length during the day shift was longer from the young to old, and it was shorter from the Evening, Intermediate, to Morning type. In the weekly rotation full-day 3-team 3-shift system and continuous full-day 3-team 3-shift system (which had earlier starting times for day shift) the sleep length of the younger workers was short. For the aged workers, sleep length during the night shift was short because they woke up early. In the weekly rotation full-day 2-team 2-shift system that had a short working interval, the reduction of sleep length during night shift was greater than that of the other shift systems. However, the scores on the Morningness-Eveningness Questionnaire showed a significantly negative correlation only in the bedtime during day shift among the sleep habit parameters for the independent variable by age. For the percentage of subjects that reported 'become sleepiness', the degree and time of sleepiness during the night shift were greater and earlier for the older than for the younger workers, and greater for the Morning than for the Evening type. The percentage of subjects who took a catnap during night shift, as well as the length of their catnap, were also higher and longer for the older groups, and higher and longer for the Morning type than for the Evening type. From these results, we surmised that the sleep habit parameters were influenced the age or shift systems rather than the chronotype. The sleep length during the night shift was shorter for the aged than for the young. In the shift systems that have a short working interval, the nocturnal was remarkably shorter for the young than the aged. The aged had not adapted their sleep for the night shift compared to the young, this suggested by the aged's strong complaint of sleepiness and by the fact that a larger percentage of aged subjects said they took catnaps during night shift compared to the younger workers.     

Predicting cerebral blood flow response to orthostatic stress from resting dynamics: effects of healthy aging

The transfer function relating arterial pressure (AP) to cerebral blood flow velocity (CBFV) during resting conditions has been used to predict the CBFV response to hypotension. We hypothesized that this approach could predict the CBFV response to posture change in elderly individuals if impaired autoregulation allowed changes in AP to be passively transferred to CBFV. AP (Finapres) and CBFV (middle cerebral artery transcranial Doppler) were measured in 10 healthy young (age 24 +/- 1 yr) and 10 healthy elderly (age 72 +/- 3 yr) subjects during 5 min of quiet sitting and 1 min of active standing while breathing was paced at 0.25 Hz. Transfer functions between AP and CBFV changes during sitting were estimated from each full waveform in both low-frequency (LF; 0.05-0.2 Hz) and heartbeat-frequency (HBF; 0.7-1.4 Hz) ranges. The impulse-response function was used to compute changes in CBFV during posture change. The LF transfer function did not predict orthostatic changes in CBFV in either group, suggesting normal cerebral autoregulation. In the HBF range, the prediction was high in elderly (R = 0.65 +/- 0.23) but not young subjects (R = 0.19 +/- 0.35; P < 0.003, young vs. elderly). Thus rapidly acting regulatory mechanisms that reduce the transmission of beat-to-beat changes in AP to CBFV may be engaged during posture change in young but not elderly subjects.     

The effects of skin pressure by clothing on circadian rhythms of core temperature and salivary melatonin

The present experiment investigated the effects of skin pressure by foundation garments (girdle and brassiere) on the circadian rhythms of core temperature and salivary melatonin. Ten healthy females (18-23 years) maintained regular sleep-wake cycles for a week prior to participation in the experiment. The experiments were performed from June to August 1999 using a bioclimatic chamber controlled at 26.5 degrees C +/- 0.2 degrees C and 62% +/- 3% RH. Ambient light intensity was controlled at 500 lux from 07:30 to 17:30, 100 lux from 17:30 to 19:30, 20 lux from 19:30 to 23:30; there was total darkness from 23:30 to 07:30. The experiment lasted for 58h over three nights. The participants arose at 07:30 on the first full day and retired at 23:30, adhering to a set schedule for 24h, but without wearing foundation garments. For the final 24h of the second full day, the subjects wore foundation garments. Rectal and leg skin temperatures were measured continuously throughout the experiment. Saliva and urine were collected every 4h for the analysis of melatonin and catecholamines, respectively. Skin pressure applied by the foundation garments was in the range 11-17 gf/cm2 at the regions of the abdomen, hip, chest, and back. The main results were as follows: (1) Rectal temperatures were significantly higher throughout the day and night when wearing foundation garments. (2) The nocturnal level of salivary melatonin measured at 03:30 was 115.2 +/- 40.4 pg/mL (mean +/- SEM, N = 10) without and 51.3 +/- 18.4 pg/mL (mean +/- SEM, N = 10) with foundation garments. (3) Mean urinary noradrenaline excretion was significantly lower throughout the day and night when wearing foundation garments (p < .05), but mean urinary adrenaline excretion was not different. The results suggest that skin pressure by clothing could markedly suppress the nocturnal elevation of salivary melatonin, resulting in an increase of rectal temperature.