Growth-related changes in the influence of obesity on signs suggesting sleep-disordered breathing and sleepiness in young individuals with Down syndrome.

BACKGROUND: Sleep-disordered breathing (SDB) is highly prevalent in individuals with Down syndrome (DS), who cease growing earlier than individuals without DS. These characteristics may be associated with increased obesity and subsequent SDB signs, such as snoring and apnoea or excessive daytime sleepiness (EDS). Thus, we assessed the influence of growth on the association between obesity and SDB signs or EDS; we used questionnaires sent to young individuals with DS and their caregivers, in a cross-sectional study. METHODS: We sent out 2000 questionnaires to individuals with DS and their caregivers. The surveys included questions about SDB signs (witnessed snoring or apnoea), subjective sleeping time including witnessed midnight arousal, the Epworth sleepiness scale and witnessed napping as well as sex, age, body weight and body height. RESULTS: Of the 1222 questionnaires we received, 660 were from young individuals and were included in the analysis. SDB signs were highly prevalent (77.1%), and frequency of SDB signs increased with growth (P-trend: P = 0.02) in individuals with DS. Multivariate analyses showed that EDS (Epworth sleepiness scale > 10 points) was associated with body mass index Z-score (Z-BMI) in the 6-9 years age group (odds ratio [OR] 95% confidence interval [95% CI]: 1.69 [1.09-2.62], P = 0.02). Conversely, SDB signs were associated with Z-BMI in the 13-15 (OR [95% CI]: 1.99 [1.06-3.72], P = 0.03) and 16-18 years age groups (OR [95% CI]: 3.04 [1.22-7.59], P = 0.02). For the 19-21 years age group, SDB signs were associated with only male sex (OR [95% CI]: 7.28 [1.22-43.38], P = 0.03). CONCLUSIONS: This study showed that the association between Z-BMI and SDB or EDS was age dependent. In early school-age children with DS, high Z-BMI could not accurately predict the presence of SDB, but it was associated with EDS. In the pubescent period (i.e. 13-18 years), high Z-BMI was associated with SDB signs but not with EDS. Overall, obesity affected SDB signs and EDS differently based on age in young individuals with DS.

A nationwide, cross-sectional survey on unusual sleep postures and sleep-disordered breathing-related symptoms in people with Down syndrome.

BACKGROUND: People with Down syndrome (DS) often have sleep-disordered breathing (SDB). Unusual sleep postures, such as leaning forward and sitting, are observed in people with DS. This study aimed to clarify the prevalence of unusual sleep postures and their relationships with SDB-related symptoms (SDB-RSs), such as snoring, witnessed apnoea, nocturnal awakening and excessive daytime sleepiness. METHODS: A questionnaire, including demographic characteristics and the presence of unusual sleep postures, as well as SDB-RSs, was completed by 1149 parents of people with DS from Japan. RESULTS: Unusual sleep postures were recorded in 483 (42.0%) people with DS. These participants were significantly younger and had a history of low muscle tone more frequently than people without unusual sleep postures. In all ages, the leaning forward posture was more frequent than sitting. People with DS with unusual sleep postures suffered from SDB-RSs. Those who slept in the sitting posture had more frequent SDB-RSs than did those who slept with the leaning forward posture. Snoring, witnessed apnoea and nocturnal awakening were observed in 73.6, 27.2 and 58.2% of participants, respectively. Snoring increased with aging. Witnessed apnoea was more common in males and in those with hypothyroidism than in females and in those without hypothyroidism. CONCLUSIONS: Our study shows that there is a close relationship between unusual sleep postures and SDB-RSs. We recommend that all people with DS with unusual sleep postures should be checked for the presence of SDB.

Health-related quality of life in patients with lower rectal cancer after sphincter-saving surgery: a prospective 6-month follow-up study.

This longitudinal descriptive study examined whether rectal cancer patients report changes in health-related quality of life (HRQOL) over a 6-month period after different types of sphincter-saving surgery (SSS): intersphincteric resection (ISR), ultra-low anterior resection (ULAR) and low anterior resection (LAR). It also compares HRQOL among the three groups of patients. Seventy-three patients from two hospitals in Japan completed questionnaires on HRQOL and defecation symptoms immediately before surgery and 1 and 6 months afterwards. Results showed that ISR patients had significantly worse HRQOL scores than ULAR and LAR patients and more defecation symptoms that persisted during the 6 months post-SSS. Thus, patients undergoing ISR require psychological and social support, including skills in competent self-management, during the early post-operative period. Furthermore, defecation problems substantially influence HRQOL. The first month post-SSS is particularly challenging. The assumption that HRQOL is better after SSS compared to living with a permanent stoma might not be valid.

Effects of 6-h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity.

The purpose of this study was to investigate the effects of 6-h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric-induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL.

Rate of health insurance reimbursement and adherence to anti-hypertensive treatment among Japanese patients.

BACKGROUND: Although several studies have reported the effects of free medical care on compliance in patients with hypertension, no study has reported the effects of an economic incentive, such as subsidized medical costs, on compliance with medication protocol, in patients with hypertension. The unique characteristics of the Japanese health insurance system provide for a 10% decrease in the subsidy for medication immediately on retirement (approximately 60 years of age) for insured patients, and a 100% subsidy for insured patients who are 70 years of age or older. We examined the association between level of health insurance coverage and follow-up rate of medical treatment among Japanese patients with hypertension. METHODS: The subjects, from throughout Japan, were patients with hypertension (n=1236). The study was conducted in 1991. The odds of completing a 1-year treatment in relation to the rate of health insurance reimbursement were calculated using multiple logistic regression analysis. RESULTS: We found the following. (1) Compared with the base group, the odds of completing a 1-year treatment increased to 2.62 or 2.51 in the group whose reimbursement rate was 100%. (2) Compared with the base group, the odds of completing a 1-year treatment was no larger than 1 in the group whose reimbursement rate had been 100% for more than 6 years ('76-'). (3) Compared with the base level, the odds of completing a 1-year treatment increased to 1-1.81 in the group whose liability decreased to 80%. CONCLUSION: Although the results imply that even a small economic incentive might be effective in securing a patient's compliance with anti-hypertensive medical treatment, the effect appear limited in both duration and magnitude.

Magnesium deficiency in adult rats promotes the induction of ventricular tachycardia by the administration of epinephrine.

The effects of magnesium deficiency on epinephrine-induced ventricular tachyarrhythmia were investigated in adult rats. Forty-two adult Wistar rats were fed a magnesium-deficient diet while 30 rats were fed a standard diet for 20 days. The plasma magnesium concentration was lower in the magnesium-deficient rats (0.22+/-0.01 mmol/l) than in the control rats (0.76+/-0.03 mmol/l, P < 0.001). Using a telemetry system, electrocardiograms and arterial blood pressure were recorded on a polygraph in an unrestrained condition. Epinephrine was infused intravenously starting at 5 microg/kg per minute. The QT interval was prolonged to 50+/-1 ms in the magnesium-deficient rats compared with 44+/-1 ms in the control rats (P < 0.001). Before the administration of epinephrine, no ventricular tachyarrhythmias or seizures were found in either the control or the magnesium-deficient rats. The incidence of epinephrine-induced sustained ventricular tachycardia (VT) was higher in the magnesium-deficient rats (86%) than in the control rats (43%, P < 0.01). However, this VT did not result in sudden death. Seizures always preceded death in both the magnesium-deficient and control rats while the arrhythmias observed immediately before death were mainly bradyarrhythmias. The present study in an adult rat magnesium-deficient model revealed that magnesium deficiency enhances the susceptibility to epinephrine-induced ventricular tachyarrhythmias.

Cardiac complications after hepatic resection.

During a period of 94 months between 1985 and 1993, 474 hepatic resections were performed in 451 patients, of whom 23 (5 per cent) had cardiac problems: ischaemic heart disease in 16 (previous myocardial infarction in five and angina pectoris in 11), arrhythmic disorders in three, valvular disease in three (previous mitral valve replacement in two) and hypertrophic cardiomyopathy in one. The cardiac patients had a higher incidence of cardiac complications (24 versus 0 per cent, P < 0.0001) including two myocardial infarctions, and of non-cardiac complications consisting of postoperative liver failure (16 versus 4 per cent, P < 0.01) and bile leak (16 versus 5 per cent, P = 0.02), as well as hospital death (16 versus 3 per cent, P < 0.001). However, long-term survival was similar in the two groups. Patients with preoperative cardiac conditions appear to be at increased risk for early postoperative morbidity and mortality after hepatic resection.

Sudden sound-induced death in magnesium-deficient rats after repetitive episodes of seizures result from brain dysfunction.

To clarify the changes occurring in EEG and ECG from seizure induction to sudden death, 25 weanling male Sprague-Dawley rats were fed a severely Mg-deficient diet for 18 days. In nine of 25 Mg-deficient rats, both EEG and ECG were recorded from the beginning of seizures induction until sudden death. When flattening of EEG became after seizure occurrence, all nine Mg-deficient rats did not recover and death occurred within a few minutes. These results may support the idea that sudden death in Mg-deficient rats resulted from brain dysfunction after repetitive episodes of noise-induced seizures and not from simple apnoea due to tonic contraction of respiratory muscle.

In vivo assessment of prevention of white-noise-induced seizure in magnesium-deficient rats by N-methyl-D-aspartate receptor blockers.

The behavioral changes associated with seizures induced by auditory stimulation in magnesium (Mg)-deficient rats originate in deep brain structures and secondarily project to neocortex. In the present study, we examined the roles of N-methyl-D-aspartate (NMDA) receptors in this seizure model. The intraperitoneal administration of the competitive NMDA receptor blocker DL-2-amino-7-phosphonoheptanoic acid (36 and 72 mg/kg) and the non-competitive NMDA receptor blocker MK-801 (1.35 and 2.7 mg/kg), completely prevented the induction of seizure and bradyarrhythmia or sudden death resulting from seizure. Therefore, the white-noise-induced seizures in Mg-deficient rats are linked to increased neuronal excitability via the NMDA receptor.

Optimal coupling of the left ventricle with the arterial system.

In the human the heart contracts more than 2.0 billion times during the lifetime. The total amount of energy required in this period is equivalent to lift a huge tanker (more than 200 thousand tons) above your head. Thus there is no question that the heart requires a huge amount of energy. Since minimization of energy requirements would be one of the major design goals of the cardiovascular system, we investigated energy efficiency of ventriculo-arterial coupling under various conditions. In normal conscious dogs, the arterial system extracted maximal work from the left ventricle during exercise as well as at rest. At the same time, the energy consumption of the left ventricle to support the peripheral demand was minimum. This optimal coupling condition was well maintained despite changes in blood volume. The baroreflex system appeared to play a crucial role in this optimization. In the presence of left ventricular dysfunction, however, this optimality was no longer maintained. We conclude that the efficiency of cardiac contraction is fairly well maintained under various stresses as long as left ventricular function is normal.

Acute myocardial infarction with a hemodynamic pattern resembling constrictive pericarditis.

A 49-year-old woman experienced acute myocardial infarction with a hemodynamic pattern resembling constrictive pericarditis. To clarify its mechanism, we performed right atrial pacing and volume challenge test during the chronic state. Although these two interventions elevated diastolic pressures of the both ventricles, the dip and plateau pattern was not reproduced. Factors other than ischemia may be important in producing a hemodynamic pattern resembling constrictive pericarditis in acute myocardial infarction.

Identification of the rate-dependent functional refractory period of the atrioventricular node in simulated atrial fibrillation.

We continuously observed successive pairs of R-R intervals during atrial fibrillation and hypothesized that the shortest R-R interval for a given preceding R-R interval in a pair represents the functional refractory period of the atrioventricular node at that preceding interval. To test this hypothesis we simulated atrial fibrillation in 28 isolated cross-perfused canine hearts and obtained an R-R interval scatterplot by plotting the R-R intervals as a function of the immediately preceding R-R interval. This scatterplot enabled us to detect a series of the shortest R-R intervals for a wide range of preceding R-R intervals, and this allowed us to estimate the rate-dependent functional refractory period of the atrioventricular node in simulated atrial fibrillation. The estimated functional refractory periods correlated well with those measured by the conventional method (r = 0.93). We conclude that the proposed method makes it possible to estimate the rate-dependent functional refractory periods of the atrioventricular node in atrial fibrillation.