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M Palta

Publications and source records attributed to M Palta.

88 records · Page 5Linked to original sources
PubMed1985

Investigating maximum power losses in survival studies with nonstratified randomization.

In studies with nonstratified randomization, imbalances may occur which lead to power loss. We investigate how much power may be lost at worst, that is, with small but nonnegligible probability. The situation considered is a two-treatment trial with censored survival data, and three to five strata. We also derive asymptotic results, as the sample size and/or number of strata increase. In addition, we consider how much a projected sample size needs to be increased to be confident (at a certain probability level) that the intended power will be retained, conditionally on the unbalanced configuration.

Biometry↗
PubMed1984

Abnormalities of the foveal avascular zone in diabetic retinopathy.

The dimensions of the foveal avascular zone (FAZ) were measured in fluorescein angiograms from 36 diabetic patients and 20 nondiabetic controls. The median values for longest diameter, mean diameter, and circumference were significantly greater in the diabetic group than in the control group. Longest diameters greater than 1.0 mm were found almost exclusively in eyes with proliferative diabetic retinopathy. The FAZ dimensions were strongly positively correlated with the severity of capillary nonperfusion in the posterior retina, but not with fluorescein leakage. The presence of proliferative diabetic retinopathy was also strongly correlated with capillary nonperfusion. Retinal capillary occlusion as the cause of FAZ enlargement in diabetic retinopathy is supported by these findings.

Adult↗
PubMed1984

Electroretinographic oscillatory potentials predict progression of diabetic retinopathy. Preliminary report.

The oscillatory potential (OP) amplitudes of the electroretinogram (ERG) were determined in a group of 85 diabetic patients entering the Early Treatment Diabetic Retinopathy Study (ETDRS). The rate of progression among nonphotocoagulated eyes to the Diabetic Retinopathy Study high-risk characteristics (DRS-HRC) during a ten- to 40-month follow-up period was determined. Progression occurred in 19 of 85 eyes at risk. Those eyes with abnormal OP amplitudes (less than or equal to 75 microV) at study entry had a tenfold higher rate of progression to DRS-HRC than did eyes with normal amplitudes (greater than 75 microV). Although the level of retinopathic severity at study entry was a significant factor in the rate of subsequent progression, the amplitudes of the OPs remained a significant risk factor even after correcting the initial retinopathic level. The ERG seems to be a useful clinical tool in predicting the rate of progression of diabetic retinopathy. The reduction in OP amplitudes probably is a quantitative measure of the degree of overall inner layer retinal ischemia.

Adolescent↗
PubMed1984

Urinary glucose testing inaccuracies among diabetic patients. Effect of acquired color vision deficiency caused by diabetic retinopathy.

The performance of two urinary glucose tests (Clinitest and Diastix) and several color vision and lightness discrimination tests was assessed in 43 diabetic patients and 43 age-matched controls. Most of the diabetics had proliferative diabetic retinopathy, with normal or mildly reduced visual acuity. The diabetics made significantly more errors on color interpretation of the urinary test results than did controls. The extent of errors for both diabetics and controls correlated with the severity of color vision deficiency but not with lightness discrimination deficiency. The diabetics' performance of the Clinitest test and, to a lesser extent, of the Diastix test was significantly better in bright light than in dimmer light. The type of color vision deficiency among most of the diabetics was characteristic of the acquired blue-yellow defect associated with diabetes mellitus. All of the color vision tests enabled identification of patients likely to make a large number of urine-testing errors with high sensitivity and fairly high specificity.

Adult↗
PubMed1982

Comparison of self-reported and measured height and weight.

Screening data from the Hypertension Detection and Follow-up Program in Minneapolis, MN, 1973-1974, provided an opportunity to evaluate the accuracy of self-report of height and weight. It was found that both were reported, on the average, with small but systematic errors. Large errors were found in certain population subgroups. Also, men and women differed somewhat in their pattern of misreporting. Weight was understated by 1.6% by men and 3.1% by women, whereas height was overstated by 1.3% by men and 0.6% by women. As in previous studies, it was found that the most important correlates of the amount of error were the actual measurements of height and weight. An interesting finding was that misreporting of both height and weight in men was correlated with both aspects of body size, whereas for women, it was related mainly to the characteristic in question. Certain other demographic variables, such as age and educational level, were also found to have some importance as factors influencing misreporting.

Adult↗
PubMed1981

The effect of various vegetable supplements on serum cholesterol.

Several previous studies have indicated that vegetables may lower serum total cholesterol. This study, using a Latin square experimental design, investigates the effect of three vegetable supplements (vegetable roots, vegetable leaves and stalks, whole grains) on serum lipoprotein cholesterol. The results from each vegetable supplement are compared to the results from a sucrose supplement of equal caloric content. Dietary fat, alcohol consumption, cigarette smoking, body weight, and physical activity are all controlled in the experimental design or the analysis. The results show that the effect of vegetables on serum cholesterol is not confined to one vegetable grouping or one type of lipoprotein cholesterol. Vegetable leaves and stalks are associated with lower values of very low-density lipoprotein cholesterol (and possibly low-density lipoprotein cholesterol) and total cholesterol. Whole grains are associated with lower values of low density lipoprotein cholesterol and total cholesterol. In addition to the actual cholesterol lowering effect compared to sucrose, the lack of an increase, suggests some advantage in the use of these vegetable groupings (even roots) as a replacement for fat in the diet, and vegetable leaves and whole grains as a replacement for sucrose.

Adult↗
PubMedDate not supplied

Magnitude and likelihood of loss resulting from non-stratified randomization.

We investigate the power of detecting treatment differences by the stratified logrank test for balanced samples as compared to samples with unequal allocation to treatments within strata. Given non-stratified randomization to treatments, we relate power losses to their probability of occurrence. In addition, we evaluate the likelihood of zero cells. For power calculations, we employ an asymptotic formula and complement by Monte Carlo simulations to verify results in small samples. In the cases investigated, our results show that large power losses due to imbalance are relatively unlikely with 2 strata. Small strata, however, involve a non-negligible probability of wasting all observations because of zero cells or censoring.

Clinical Trials as Topic↗
PubMedDate not supplied

Some considerations in the analysis of rates of change in longitudinal studies.

This paper discusses and compares several estimators of mean rate of change in unbalanced longitudinal data based on a model with randomly distributed regression coefficients across individuals. The estimators are unweighted and weighted means of these coefficients. The paper also evaluates commonly used variance estimates corresponding to the estimators. Results show that in situations of very slight imbalance, the choice of method is not critical. When imbalance is substantial, however, one should weight the regression coefficients by their estimated precision. An example using data from a nutritional study on premature neonates illustrates some issues encountered in the analysis of longitudinal clinical data sets.

Humans↗
PubMedDate not supplied

Blood pressure of urban Native American school children.

In 307 Native American (NA), 1784 black (B), and 7777 white (W) children in grades 1, 2, and 3 in Minneapolis schools (99% overall response rate), blood pressure (BP) was measured supine in the right arm after 5 minutes' rest by trained technicians using a random zero BP device. In addition, height, weight, pulse rate, and triceps skinfold thickness were measured. Among children aged 6 through 9 years, NA children had slightly higher systolic BP (SBP) than B or W children overall (mean SBP: NA 106, B 104, W 105 mm Hg) and for nearly all age sex groups. In contrast, Phase 4 and 5 diastolic BP (DBP) were consistently lower in NA children ( mean DBP4: NA 64, B 69, W 67 mm Hg); NA children also had lower pulse rates, greater pulse pressures, similar or slightly lower mean BP, similar height, greater weight, body mass index, and triceps skinfold. Multiple regression analyses revealed that the slightly higher SBP in NA children was explained almost entirely by greater ponderosity. However, the lower DBP could not be explained statistically by any of the variables measured.

Black People↗
PubMedDate not supplied

Sex-role stereotyping in assessments of mental health made by psychiatric-mental health nurses.

To determine the amount of sex-role stereotyping in judgments of mental health made by psychiatric-mental health nurses, 150 of these nurses, divided into three equal groups, were asked to rate ideal states of mental health in males, females, and adults, respectively. An 83 percent return rate was obtained. Results showed: 1) there was less sex-role stereotyping than in a similar study reported in 1970 with other mental health professionals; 2) judgments of mental health closely resembled assessments of social desirability; 3) healthy females were rated closer to that which was considered desirable and closer to the healthy adult pole than males or adults; 4) healthy females possessed the valued male traits without losing the female-valued characteristics; and 5) nurses who had longer experience as therapists, who were older, and who were still practicing viewed men and women as more alike rather than placing higher expectations on women.

Adult↗
PubMedDate not supplied

Death and dying: selected attitudes of Minnesota's registered nurses.

A study of attitudes toward dying patients of 1,061 Minnesota nurses who practiced in the metropolitan area (210 nurses) and outside the metropolitan area (851 nurses) revealed that they supported home care for dying children. They reported they would be willing to care for the dying adult or child in the home, but would feel more comfortable if they had added specialized preparation.

Adult↗
PubMedDate not supplied

Population-based study of sleep-disordered breathing as a risk factor for hypertension.

BACKGROUND: Clinical observations have linked sleep-disordered breathing, a condition of repeated apneas and hypopneas during sleep, with hypertension but evidence for an independent association has been lacking. Understanding this relationship is important because the prevalence of sleep-disordered breathing is high in adults. OBJECTIVE: To test the hypothesis that sleep-disordered breathing is related to elevated blood pressure independent of confounding factors. METHODS: The sample included 1060 employed women and men aged 30 through 60 years who had completed an overnight protocol as part of the Wisconsin Sleep Cohort Study. In-laboratory polysomnography was used to determine sleep-disordered breathing status, quantified as the number of apneas and hypopneas per hour of sleep (apnea-hypopnea index). Blood pressure was measured on the night polysomnography was performed. RESULTS: Blood pressure increased linearly with increasing apnea-hypopnea index (P = .003 for systolic, P = .01 for diastolic, adjusted for confounding factors). The magnitude of the linear association increased with decreasing obesity. At a body mass index (weight in kilograms divided by the square of the height in meters) of 30 kg/m2, an apnea-hypopnea index of 15 (vs 0) was associated with blood pressure increases of 3.6 mm Hg for systolic (95% confidence interval, 1.3-6.0) and 1.8 mm Hg for diastolic (95% confidence interval, 0.3-3.3). The odds ratio for hypertension associated with an apnea-hypopnea index of 15 (vs 0) was 1.8 (95% confidence interval, 1.3-2.4). CONCLUSIONS: There is a dose-response relationship between sleep-disordered breathing and blood pressure, independent of known confounding factors. If causal, the high prevalence of sleep-disordered breathing could account for hypertension in a substantial number of adults in the United States.

Adult↗