Ethnicity and socioeconomic status: impact on cardiovascular activity at rest and during stress in youth with a family history of hypertension

OBJECTIVE

The purpose of the present study was to examine the potential interaction of ethnicity and SES on hemodynamic functioning at rest and during acute stress in normotensive adolescents with a family history of essential hypertension (EH).

DESIGN

The influences of ethnicity and socioeconomic status (SES) on cardiovascular function were evaluated at rest and in response to five different laboratory stressors.

METHODS

110 (50 female) Caucasian and 162 (85 female) African-American normotensive youth (initial age 11.2+/-2.4 years) with a family history of essential hypertension (EH) were tested on two occasions, an average of 2.5 years apart. Based on previous findings, it was predicted that African Americans, particularly those of low SES, would exhibit higher resting blood pressure (BP) and greater cardiovascular reactivity to acute laboratory stressors than would Caucasians.

RESULTS

As predicted, African-American youth exhibited higher resting diastolic blood pressure (DBP) and total peripheral resistance (TPR) than Caucasians on both visits (both Ps<.04). African Americans exhibited greater systolic blood pressure (SBP) reactivity than did Caucasians to the video game stressor during both lab visits (both Ps<.02) and greater heart rate reactivity during the first lab visit (P<.01). African Americans exhibited greater SBP and/or DBP, and TPR reactivity to the cold pressor during the first lab visit and the parent-child discussion during the second visit (all Ps<.03).

CONCLUSION

As predicted, African Americans exhibited higher resting BP and TPR, and greater cardiovascular reactivity than Caucasians. Although not in the predicted direction, a pattern of interactions began to emerge on the second evaluation. For example, upper SES youth exhibited greater heart rate reactivity compared to all other groups on the social competence interview and parent-child discussion stressors. Further study is needed to clarify the role cardiovascular reactivity may play in the link between ethnicity, SES, and cardiovascular disease risk.

Racial differences in endothelin-1 at rest and in response to acute stress in adolescent males

Blacks exhibit greater vasoconstriction-mediated blood pressure (BP) increases in response to stress than do whites. Endothelin-1 (ET-1), a potent vasoconstrictive peptide, has been proposed as having a role in racial differences in stress reactivity. We evaluated the hemodynamic and plasma ET-1 levels of 41 (23 whites, 18 blacks, mean age 18.6 years) normotensive adolescent males at rest and in response to a video game challenge and forehead cold stimulation. Measurements were performed at catheter insertion and before and immediately after the 2 stressors, which were separated by 20-minute rest periods. Blacks exhibited higher absolute levels of diastolic blood pressure, total peripheral resistance index, or both in response to catheter insertion and to the video game challenge and during recovery from video game challenge and cold stimulation (P<0. 05 for all). Blacks exhibited higher absolute levels of ET-1 at every evaluation point (P<0.05 for all) and greater increases in ET-1 in response to both stressors (ps<0.05). These findings suggest that altered endothelial function may be involved in racial differences in hemodynamic reactivity to stress and possibly in the development of essential hypertension.

Patterns of body fat deposition in youth and their relation to left ventricular markers of adverse cardiovascular prognosis

The patterns of body fat deposition in healthy youth and their relation to future development of cardiovascular disease remain incompletely understood. To further evaluate these patterns, we measured indirect indexes of central and general fat deposition in healthy adolescents (mean age 15.4+/-2.3 years) with family histories of hypertension. We examined the relation between these indexes and echocardiographic markers of adverse prognosis as well as the effect of gender and ethnicity. All 225 subjects (64% black and 48% female) had > or =1 biologic parent and 1 grandparent with hypertension. Skinfold thicknesses, waist-to-hip girth ratio, Quetelet index, Ponderal index, conicity, and Z score weight - Z score height were measured. Left ventricular (LV) mass, indexed LV mass, relative wall thickness (RWT), and midwall fractional shortening (MFS) were determined using echocardiography. In both black and white subjects, the adiposity indexes were significantly correlated with posterior wall thickness, total LV mass, and indexed LV mass (p <0.05 for all). Additionally, in black subjects, central adiposity was inversely related to MFS and directly related to RWT and septal thickness. General adiposity independently predicted indexed and nonindexed LV mass, whereas central adiposity predicted MFS and RWT. Compared with subjects with normal LV geometry, those with abnormal geometry were heavier and fatter based on every index of obesity (p <0.03 for all). Thus, indexes of fat deposition are significantly correlated with LV markers of adverse prognosis in healthy youth.

A novel skin penetration enhancer: evaluation by membrane diffusion and confocal microscopy

PURPOSE

The aim of this study was to determine the in vitro transdermal efficacy of a Meyer Zall Laboratories (MZL) oil/water emulsion in two separate preparations containing the actives, coal tar and the non-steroidal anti-inflammatory drug, diclofenac sodium.

METHOD

The release rate of the two active ingredients from MZL dermatological preparations, Exorex and Athru-Derm and four comparator products was determined using an enhancer cell system, whilst specific penetration characteristics of the MZL formulation were elucidated using confocal and electron microscopy. The latter properties were explored at both the organ level, using human skin, as well as at a cellular level using a melanoma cell line.

RESULTS

While the in vitro release rates for all formulations was high, coal tar and diclofenac release from Exorex and Athru-Derm respectively was, at nearly all time intervals, significantly higher than from comparator products. Microscopy revealed the presence of spherical liposomal type structures in both the MZL lotion and a comparator gel. In the MZL lotion, the majority of these structures, referred to here as emzaloid particles, were in the order of magnitude of about 50 nm to 1 microm in diameter with a small minority exceeding these dimensions. After application of Athru-Derm to human skin, intact emzaloid particles of submicron dimensions were detected in the epidermis in association with the cell membranes. The affinity of the MZL lotion for cell membranes was further demonstrated with melanoma cells; in addition, the formulation was seen to penetrate even to the nucleus of viable cells.

CONCLUSION

Overall the data suggest that the oil/water base in MZL formulations is a highly efficient transdermal vehicle able to transport a wide range of indication- specific actives to their site of action.

Temporal stability of ambulatory blood pressure and heart rate in youths

BACKGROUND

The use of ambulatory blood pressure monitoring for pediatric populations is increasing.

OBJECTIVE

; To determine the 2-year stability of ambulatory blood pressure in youths.

METHODS

We evaluated 2-year stabilities of resting and ambulatory blood pressures in 197 youths (aged 13.9+/-2.3 years at initial evaluation). Readings were taken every 20 min during the daytime (0800-2200 h) and every 30 min at night (0000-0600 h).

RESULTS

Daytime and night-time systolic blood pressure increased (P < 0.01 for both) as did resting systolic blood pressure (P < 0.05). Measures of diastolic blood pressure did not change. Changes in systolic blood pressure were related to changes in body size. Estimates of stability for resting and ambulatory measurements were similar, ranging from 0.65 to 0.75. In addition, correlation coefficients for relationships between first and second readings for resting and ambulatory measurements were similar ranging from 0.43 and for resting heart rate to 0.72 for 24h systolic blood pressure (P < 0. 001 for each). The only significant correlation between change scores for resting and ambulatory values was that between resting and night-time diastolic blood pressures (r = 0.33, P < 0.001).

CONCLUSION

Measures of blood pressure derived from ambulatory blood pressure monitoring reflect changes in blood pressure in youths at least as well as do changes in resting blood pressure despite the high degree of variability in levels of physical activity and affective states of the children during the ambulatory recordings.

The role of maternal hostility and family environment upon cardiovascular functioning among youth two years later: socioeconomic and ethnic differences

Two hundred sixty-eight African-American and white children and their biological mothers participated in the study. The purpose of the study was to examine the potential collective impact of maternal hostile coping styles and perceptions of family functioning upon youths' cardiovascular (CV) functioning 2.4 years later, within the context of SES and ethnicity. The mother completed a set of questionnaires that included the Cook-Medley Hostility Scale and three scales from the Family Environment Scale (FES). Childrens' systolic and diastolic blood pressure (SBP and DBP) and impedance cardiography derived total peripheral resistance (TPR) was measured at rest two years later. Mothers with lower SES and African-American mothers reported higher levels of hostility compared to those with higher SES and white mothers, respectively. Lower SES mothers reported lower levels of family cohesion and expressiveness than higher SES mothers. Whites reported more family conflict and expressiveness than African Americans. African-American and lower SES youth exhibited higher SBP and DBP values than whites and higher SES youth. Among lower SES African-American youth, CV functioning tended to be impacted negatively when their mothers rated themselves high in hostility. Findings suggest that ethnicity and SES may have independent as well as interactive impacts on the influence of maternal coping styles on the CV functioning of their children, particularly those from lower SES backgrounds.

Prospective evaluation of accuracy, precision, and reproducibility of an at-home hemoglobin A1c sampling kit

BACKGROUND

The measurement of hemoglobin A1c (HbA1c) is critical to the optimal therapeutic management of diabetes. To be most useful, the HbA1c value should be available at the clinical visit. Recently, a number of at-home sampling kits have been developed that facilitate the timely availability of HbA1c results. This is a report of the accuracy, precision (among-subject), and reproducibility (within-subject) of one such kit, B-D A1c, At-Home-Test, which combines a filter paper technique for spotting capillary blood with an immunoturbidometric assay (a variation of the Cobas Integra Hemoglobin A1c method also referred to as Roche Unimate).

METHODS

The B-D A1c At-Home test kit was evaluated in a clinical trial using 1625 dried blood spot samples from 59 subjects diagnosed with type 1 or type 2 diabetes collected in an in-clinic setting. Data for replicate samples were compared against those from the standard Cobas Integra Hemoglobin A1c assay and from the BioRad Variant high-performance liquid chromatography [HPLC] assay. The effects of subjecting the dried spotted blood samples to prolonged elevated temperatures was evaluated in a separate laboratory analysis.

RESULTS

The B-D A1c At-Home results, which are highly correlated with the standard Cobas Integra Hemoglobin A1c assay, (r2 = 94.7%), demonstrate excellent within-subject reproducibility for 3- to 10-day-old samples (coefficient of variation = 2.7%), and provide a coefficient of variation for among-subjects that is 3.9%. There were no clinically significant differences (i.e., < 0.3 units) in samples aged 3 to 10 days, between venous or capillary blood samples, or from freezing and thawing or prolonged exposure of B-D A1c At-Home dried blood samples to elevated temperatures before assay.

CONCLUSIONS

The B-D A1c At-Home kit combines the accuracy, precision, and reproducibility of a clinical laboratory test with the convenience of at-home sample collection. This product may add to the convenience of both patient and health care provider by making it easier for patients to obtain their HbA1c values and have them available at their visit to the clinician.

The scope of practice of diabetes educators in the state of Georgia

PURPOSE

The purpose of this study was to identify and describe the scope of practice trends of diabetes educators in the state of Georgia.

METHODS

The Diabetes Educator Responsibilities Questionnaire (DERQ) was sent to 221 members of the American Association of Diabetes Educators listed in the 1995 membership directory in Georgia. Of the 221 members, 97 returned completed questionnaires. This population of healthcare professionals comprised the sample population.

RESULTS

In assessing the primary responsibilities of the sample, more than 50% of the respondents performed six of the nine educator roles. Less than 50% of the respondents indicated that they "Always" or "Frequently" used behavior modification strategies in teaching people with diabetes.

CONCLUSIONS

The questionnaire used in this study should be expanded to elicit more detailed information regarding decisions to use or not use behavior modification techniques in diabetes education.

Acute effects of transcendental meditation on hemodynamic functioning in middle-aged adults

OBJECTIVE

Increased peripheral vasoconstriction (ie, total peripheral resistance, or TPR) has been implicated as playing an important role in the early development of essential hypertension. Some studies have demonstrated that Transcendental Meditation (TM) reduces high blood pressure, but the hemodynamic adjustments behind these blood pressure reductions have not been elucidated. The aim of this study was to provide a preliminary investigation of the acute effects of TM on TPR.

METHODS

Subjects were 32 healthy adults (16 women and 16 men; 30 white and two African American; mean age, 46.4 +/- 3.9 years). Subjects were divided into a TM group of long-term TM practitioners (eight white women, nine white men, and one African American man; mean years of twice-daily TM practice, 22.4 +/- 6.7) and a control group (eight white women, five white men, and one African American man). Hemodynamic functioning was assessed immediately before and during three conditions: 20 minutes of rest with eyes open (all subjects), 20 minutes of TM (TM group), and 20 minutes of eyes-closed relaxation (control group).

RESULTS

During eyes-open rest, the TM group had decreases in systolic blood pressure (SBP) and TPR, compared with increases in the control group (SBP: -2.5 vs. +2.4 mm Hg, p < .01; TPR: -0.7 vs. +0.5 mm Hg/liter per minute, p < .004). During TM, there was a greater decrease in SBP due to a concomitantly greater decrease in TPR compared with the control group during eyes-closed relaxation (SBP: -3.0 vs. +2.1 mm Hg, p < .04; TPR: -1.0 vs. +0.3 mm Hg/liter per minute, p < .03).

CONCLUSIONS

TPR decreased significantly during TM. Decreases in vasoconstrictive tone during TM may be the hemodynamic mechanism responsible for reduction of high blood pressure over time. The results of this study provide a preliminary contribution to the understanding of the underlying hemodynamic mechanisms responsible for the beneficial influence of TM on cardiovascular risk factors.

Effects of race, sex, and socioeconomic status upon cardiovascular stress responsivity and recovery in youth

Cardiovascular (CV) responsivity to and recovery from acute laboratory stressors, as derived from aggregate scores of CV functioning during and after postural change, video game challenge, social competence interview, and parent-child conflict discussion, were evaluated in 272 youths [mean age 13.5 +/- 2.6 years; 162 Blacks (77 males, 85 females), 110 Whites (60 males, 50 females)], all with a positive family history of essential hypertension. Blacks demonstrated greater systolic and diastolic blood pressure (SBP, DBP) and lower heart rate responsivity compared to Whites (all P values < 0.05). A race by neighborhood socioeconomic status (SES) interaction for SBP responsivity was also observed where low SES Whites and high SES Blacks had the greatest responsivity compared to their same race cohorts. Additionally, upper SES Whites had the lowest total peripheral resistance responsivity. For recovery, Blacks and males exhibited higher SBP during recovery compared to Whites and females, respectively. These findings extend previous studies and provide further support for the hypothesis that recovery from stress is a potentially informative component of the contribution of stress responsivity to cardiovascular disease.

Explanatory style among elite ice hockey athletes

Mentally tough' athletes show resilience and an ability to compete during adverse conditions. The present study investigated mental toughness and assessed causal explanations for positive and negative reactions to imagined events using Seligman's Attributional Style Questionnaire. Pessimistic Explanatory style on this scale is a risk factor for negative affect and behavior following negative events. 38 elite athletes in ice hockey were rated for mental toughness by the National Hockey League's scouts on consensually derived criteria. The comparison of players above and below the median split on mental toughness showed composite explanations for negative events that were more internal, stable and global for players above the median. Contrary to predictions, these results suggest that a Pessimistic Explanatory style may benefit hockey performance.

Central adiposity and hemodynamic functioning at rest and during stress in adolescents

OBJECTIVE

To examine the impact of central adiposity upon hemodynamic functioning at rest and during stress in adolescents.

DESIGN

Cross-sectional, correlational study.

SUBJECTS

46 White and 49 Black normotensive adolescents with family histories of essential hypertension.

MEASUREMENTS

Systolic and diastolic blood pressure (SBP, DBP), cardiac output and total peripheral resistance responses were assessed at rest, during postural change, video game challenge and forehead cold stimulation. Specific lower and higher waist-to-hip ratio (WHR) tertiles were created for each gender and then integrated for analyses. This resulted in a lower WHR tertile of 11 Whites and 21 Blacks and an upper WHR tertile of 15 Whites and 17 Blacks.

RESULTS

No differences in age, gender or ethnicity proportions were found between tertile groups (all P > 0.21). The upper WHR group showed greater body weight, waist and hip circumferences, body mass index (BMI), triceps skinfold and body surface area (all P < 0.001). Controlling for peripheral (that is, triceps skinfold) and overall (that is, BMI) adiposity, the upper WHR group exhibited greater SBP (that is, peak response minus mean pre-stressor level) to all three stressors and greater DBP reactivity to postural change and cold pressor (all P < 0.05).

CONCLUSION

Central adiposity appears to adversely influence hemodynamic functioning during adolescence. Underlying mechanisms responsible for these associations require exploration.

The development of a community child and family mental health service

The Community Child and Family Service is a primary care and community-based child mental health service working in a socio-economically disadvantaged area of inner London. This paper outlines the strategic framework and value base from which the service has developed. The clinical projects set up by the service in general practice, community and education settings are described, as are the training and supervision programmes that have been undertaken. The framework for evaluating the clinical and economic outcomes of the projects is outlined. There has been a positive response from purchasers, providers and clients to the introduction of this Service. The relationship between community- and hospital-based child mental health services is discussed, as is the future direction of the Service.

Subchronic toxicity of benzothiophene on rats following dietary exposure

The systemic and neurobehavioral effects of benzo[b]thiophene (routinely referred to as benzothiophene) were studied in rats following 13-wk oral exposure. Male (170 +/- 16 g) and female (146 +/- 12 g) Sprague-Dawley rats (10 animals per group) were fed diet containing 0.5, 5, 50, or 500 ppm benzothiophene for 13 wk. Control animals were given rat feed plus vehicle (corn oil) only. No clinical signs of toxicity and neurobehavioral effects were observed using screening tests that included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. Elevated serum aspartate aminotransferase activity and bilirubin level were observed in highest dose females. Except for a statistically significant decrease in hematocrit in the highest dose males, benzothiophene exerted no marked effects on hematological parameters. Benzothiophene exposure did not result in alterations in hepatic alkaline phosphatase activity, or the typical hepatic phase I (aniline hydroxylase, ethoxyresorufin O-deethylase, pentoxyresorufin O-dealkylase, aminopyrine N-demethylase) and phase II (UDP-glucuronosyltransferase, glutathione S-transferase) drug-metabolizing enzyme activities. No significant elevation in urinary ascorbic acid, protein, and N-acetylglucosaminidase activity was detected in the treated animals. Peribiliary fibrosis was the most significant histological change and occurred in the liver of females in the 50 and 500 ppm groups. Mild epithelial hyperplasia in the renal pelvis was detected in the majority of 5 and 50 ppm females, with epithelial hyperplasia in the urinary bladder observed in the 50 ppm females. In males, increased incidence and severity of mild binucleation of hepatocytes and mild thickening of the basement membrane in kidney cortex were observed at 500 ppm. Benzothiophene was not detected in the urine of high-dose animals at the termination of the experiment. Based on the kidney, hepatic, and hematocrit changes, the no-observed-adverse-effect level (NOAEL) in the diet was determined to be 0.5 ppm (0.04 mg/kg/d) for females and 50 ppm (3.51 mg/kg/d) for males.

The risk for outpatient antibiotic-treated infections following a course of oral corticosteroids among children with asthma

Short courses of oral corticosteroids are widely used to treat asthma. The objective of this study was to assess if one course of oral corticosteroids increases asthmatic children's risk for infections treated with outpatient antibiotics. Using New York State Medicaid claims data on asthmatic children 2-15 years old, we made cohorts of oral corticosteroid users and nonusers. We determined the percentage of children who filled antibiotic prescriptions in the 30 days after index dates. Index dates were dates oral steroids were started (for steroid users) or matched dates (for nonusers). Odds ratios were adjusted for age, month of index date, and prior antibiotic use. Among children not receiving antibiotics on index dates, antibiotic prescriptions were filled in the next 30 days for 438 (20%) of 2145 steroid nonusers and 130 (19%) of 698 steroid users (p=0.30); compared to nonusers, steroid users had an adjusted odds ratio of subsequent antibiotic use of 0.92 (95% confidence interval [CI] 0.73-1.15). Among children receiving antibiotics on index dates, antibiotic prescriptions were filled in the next 30 days for 116 (26%) of 451 steroid nonusers and 50 (19%) of 260 steroid users (p=0.05); compared to nonusers, steroid users had an adjusted odds ratio of subsequent antibiotic use of 0.65 (95% CI 0.53-0.97). We conclude that one course of oral corticosteroids does not increase asthmatic children's risk for infections treated with outpatient antibiotics.

The GalR2 galanin receptor mediates galanin-induced jejunal contraction, but not feeding behavior, in the rat: differentiation of central and peripheral effects of receptor subtype activation

The neuropeptide galanin mediates a diverse array of physiological functions through activation of specific receptors. Roles of the three recently cloned galanin receptors (GalRs) in rat intestinal contraction and food intake were examined using GalR-selective ligands and the results were compared with the pharmacological profiles of defined GalRs. The action profile of these ligands in jejunal contraction resembled only that of GalR2 and only a high level of GalR2 mRNA was detected in the tissue, supporting GalR2 as the receptor mediating jejunal contraction. The action profile for food intake in rats excluded GalR2, GalR3 and the putative pituitary galanin receptor as the 'feeding receptor', suggesting that either GalR1 or an unidentified GalR is responsible for mediating this function.

Effects of Theraband and lightweight dumbbell training on shoulder rotation torque and serve performance in college tennis players

The purpose of this study was to determine whether a 4-week isotonic resistance training program using Theraband elastic tubing and lightweight dumbbells would significantly increase concentric shoulder rotator strength or velocity of serve or both in a group of elite-level tennis players. Twenty-two male and female varsity college tennis players were randomly assigned to control or 4-week training groups. Subjects were pre- and posttested in concentric internal and external rotation torque using an isokinetic dynamometer. Functional performance was assessed before and after training by recording the peak and average velocities of eight maximal serves. The experimental group exhibited significant gains in internal rotation torque at both slow (120 deg/sec) and fast speeds (300 deg/sec) for total work and in peak torque to body weight ratio and torque acceleration energy at the fast speed. This group also exhibited significant gains in external rotation torque for the same parameters at fast speed. Regarding speed to serve, the experimental group exhibited significantly greater increase in peak speed (+6.0% compared with -1.8%) and average speed (+7.9% compared with -2.3%) compared with the control group. Men exhibited greater internal and external rotation torque on all parameters and in peak and mean speed of serve on both evaluations. Men also exhibited greater imbalance in external to internal rotation torque ratios. In conclusion, resistance training using Theraband tubing and lightweight dumbbells may have beneficial effects on strength and functional performance in college-level tennis players.

Psychological distress in patients with chronic, nonalcoholic, uncomplicated liver disease

To study whether the presence of significant disease in a major organ, possibly with minimal or no clinical symptoms, would be associated with psychological disturbance, 80 subjects suffering from chronic hepatitis or cirrhosis, of nonalcoholic etiology were interviewed. Of these, 64 had either minimal or no physical symptoms. Patients completed the Brief Symptom Inventory (BSI) and the Impact of Event Scale (IES), questionnaires, which measure symptoms of psychological distress. It was found that 50% of the liver subjects were defined as cases by the BSI criteria including 15% who were defined as severe cases. There were no gender differences. Forty-five percent of asymptomatic liver subjects were defined as cases. Psychological distress was significantly pronounced in subjects with less than 12 years of education. This study points to a significant incidence of psychological distress, even in clinically asymptomatic subjects, suffering from chronic, nonalcoholic, uncomplicated liver disease.

Developing information materials to present the findings of technology assessments to consumers. The experience of the NHS Centre for Reviews and Dissemination

We discuss some of the issues that have arisen during the development and introduction into practice of information materials for health professionals and patients that aim to promote clinical effectiveness and informed patient participation in clinical decision making.

Randomised trial of isoniazid versus rifampicin and pyrazinamide for prevention of tuberculosis in HIV-1 infection

BACKGROUND

Tuberculosis is a common complication of HIV-1 infection, especially in developing countries. Practical and effective chemoprophylaxis regimens for HIV-1-related tuberculosis are needed. Our aim was to test the efficacy of isoniazid versus rifampicin with pyrazinamide for prevention of tuberculosis in HIV-1-positive individuals.

METHODS

We compared the efficacy of 6 months of isoniazid with 2 months of rifampicin and pyrazinamide for prevention of tuberculosis in HIV-1-seropositive individuals. Eligible participants were aged 16-77 years, HIV-1 seropositive, had a positive purified-protein derivative (PPD) skin test reaction of at least 5 mm, and had a normal chest radiograph. Participants were randomly assigned partially supervised twice weekly isoniazid for 24 weeks or twice weekly rifampicin and pyrazinamide for 8 weeks. Participants were followed up for up to 4 years for the development of tuberculosis and survival.

FINDINGS

Tuberculosis developed in 14 (3.8%) of 370 participants assigned isoniazid and 19 (5.0%) of 380 participants assigned rifampicin and pyrazinamide (Cox model rate ratio 1.3 [95% CI 0.7-2.7]). The Kaplan-Meier estimate of the risk of tuberculosis during the first 10 months after entry was 3.7% among participants who received rifampicin and pyrazinamide compared with 1.0% (p=0.03) among participants who received isoniazid, and 5.4% versus 5.1%, respectively (p=0.9) at 36 months after entry. Higher rates of tuberculosis were observed in people with baseline CD4 percentages (of total lymphocytes) of less than 20 (rate ratio 4.0 [95% CI 1.8-9.0]). There were no significant differences in total mortality at any time.

INTERPRETATION

Twice-weekly isoniazid preventive therapy for 6 months or rifampicin and pyrazinamide for 2 months provided similar overall protection against tuberculosis in HIV-1-infected, PPD-positive adults. The better protection among recipients of isoniazid during the first 10 months was most likely secondary to the longer duration of chemoprophylaxis. Preventive therapy for HIV-1-seropositive, PPD-positive individuals could be practical in developing countries with a once weekly clinic visit, but optimum duration of chemoprophylaxis has not been determined.

Hour-to-hour variability of oxygen saturation in sleep apnea

STUDY OBJECTIVES

Methods used to express the severity of oxygen desaturation during polysomnography include the average oxygen saturation (AO2), lowest oxygen saturation (LO2), and the percent of the total time with oxygen saturation level lower than 90% (T<90%). We wanted to determine which one of these methods is least variable during different hours of monitoring.

DESIGN

Prospective, observational study.

SETTING

Sleep center at a medical university.

PATIENTS

One hundred fifty patients with apnea-hypopnea index from 5 to 130.

MEASUREMENTS

AO2, LO2, and T<90% were calculated during each of the 8 h of polysomnography. Data for each hour were compared and the Cronbach alpha coefficients were calculated.

RESULTS

There was a high degree of correlation among the three methods as well as between each method and the severity of sleep apnea. The mean+/-SD values for each method were as follows: AO2, 92.7+/-5.6; LO2, 68.5+/-19.3; and T<90%, 15.7+/-24.2. The alpha coefficients for these methods were AO2, 0.98; LO2, 0.88; and T<90%, 0.98. In all methods, the data of the first hour were significantly different from the data of the subsequent hours.

CONCLUSION

Both AO2 and T<90% methods show less hour to hour variability compared with LO2, and there is more variability in the first hour. Since the AO2 values >90% may not convey the severity of O2 desaturation, T<90% may be the best method of expressing oxygen saturation changes during polysomnography.