Viswanathan Ramakrishnan

Relationships of Race and Socioeconomic Status with Prevalence, Severity, and Symptoms of Asthma in Chicago School Children

BACKGROUND Asthma mortality rates in Chicago are among the highest in the United States, with substantially greater rates in poor and minority populations. How much of the differential can be attributed to differences in prevalence versus severity or access to care has not been determined. OBJECTIVE To examine rates of asthma prevalence, severity, and symptoms and to explore the relationships of these rates to race and socioeconomic status in a random sample of Chicago school children. METHODS Self-administered survey. RESULTS Overall, rates of asthma were higher than previously reported, with 16% of students in the stratified cluster random sample of 3,670 children in the 7th and 8th grades having had asthma. Prevalence rates were significantly higher in schools with >98% African Americans than in other schools, with the highest prevalence rates seen in African American schools in low income neighborhoods. Rates were associated with the percent of African American children in the school and with median income of the schools census tract. Relationships were most consistent with indices of more severe disease. CONCLUSIONS Asthma prevalence is higher than previously noted, with rates greatest in minority and low income populations. Differences are more striking for measures of severity than for symptoms of wheezing, but are far less than previously reported differences in mortality, suggesting that additional factors, such as differential access to continuous health care, may be affecting high death rates from asthma in Chicago.

Prevalence of asthma and other allergic diseases in an adolescent population: association with gender and race

OBJECTIVES To estimate the prevalence and severity of asthma in an adolescent population by sex and race. METHODS Cross-sectional, population-based survey of school children. SETTING Midwestern city experiencing damage from the 1993 Mississippi River flood. PARTICIPANTS 2,693 children attending grades 7 to 12. MEASUREMENTS Questions from the International Study of Asthma and Allergies in Childhood (ISAAC). RESULTS Two thousand six hundred ninety-three children were surveyed, for a response rate of 90%. In this population, 16.4% reported having ever been diagnosed with asthma; 25% reported wheezing in the last 12 months; 32% reported symptoms of rhinitis in the last 12 months; and 22% reported ever having hay fever. The prevalence rate for current asthma was 12.6%. Female students had significantly greater prevalence rates for current asthma (16.4% vs 9.0%, OR = 1.85); ever-diagnosed asthma (18.5% vs 14.3%, OR = 1.36); wheezing > or = 4 times in the last 12 months (12.0% vs 5.6%, OR = 1.95); current rhinitis (38.7% vs 25.4%, OR = 1.73); and hay fever (26.4% vs 18.4%, OR = 1.57). All associations with sex remained significant, except ever-diagnosed asthma, after controlling for other known risk factors in logistic regression. African-Americans had higher prevalence rates than other races with differences reaching statistical significance for ever-diagnosed asthma and current asthma; however, these relationships did not remain significant after controlling for other known risk factors in logistic regression. CONCLUSIONS Our prevalence rates were similar to those reported by other studies that used the ISAAC questionnaire. Female students reported significantly more asthma, wheezing, rhinitis, and hay fever than male students. Female students also reported more severe symptoms and a greater number of emergency room and hospital admissions.

Familial determinants of moderate and intense physical activity : a twin study

This twin study estimates familial clustering of moderate and intense leisure-time physical activity and investigates quantitatively its genetic and environmental components. Study subjects are 3,344 male twin pairs aged 33-51 yr. Moderate activity levels were assessed with six questions about discretionary walking or stair climbing for exercise. Five questions assessed regular participation in specific, intense athletic activities (running, bicycling, swimming, racquet, and other sports). Familial aggregation is estimated by odds ratio of one twin engaging in an activity when his co-twin does. Monozygotic and dizygotic twin correlations were compared to estimate genetic and nongenetic sources of phenotypic variation. For each activity, the familial aggregation odds ratio was statistically significant with values between 2.9 to 4.6 for intense activities and between 1.4 to 1.9 for all moderate activities but one. Monozygotic twin correlations were higher than dizygotic, suggesting genes play a role in the observed phenotypic variation. For four questions, and a compromise scale of moderate activity, the difference between correlations was statistically significant (P < 0.05). In this cohort, much of the phenotypic variability for both moderate and intense activities is a result of familial effects. Genes may influence regular participation in specific intense exercises more than moderate activity, such as walking for exercise.

Asthma prevalence and risk factors in selected Head Start sites in Chicago

Prevalence of and risk factors for asthma were examined in 1085 Head Start families at 18 Head Start sites in four high-risk community areas in 1994. A total of 13.9% of the families reported diagnosed asthma in their Head Start child and 18.8% reported that their child wheezed in the last 12 months. A total of 26.9% of respondents reported asthma in the immediate family of the child. Low birth weight (1500-2499 g), very low birth weight (<1500 g), and self-reported exposure to dampness or mold in the last 12 months were significantly associated with self-reported diagnosed asthma (OR = 1.93; 95% CI 1.17-8.73), (OR = 4.5; 95% CI 1.25-16.3), and (OR = 1.94; 95% CI 1.23-3.04), respectively. The young age of the children in Head Start, as well as the high prevalence of asthma in their families, suggest that the Head Start programs offer an unusual opportunity for asthma prevention programs.

Ultrasonographic detection of abnormal fetal growth with the gestational age-independent, transverse cerebellar diameter/abdominal circumference ratio

OBJECTIVES We prospectively evaluated the accuracy of a gestational age-independent method of detecting abnormal growth, the transverse cerebellar diameter/abdominal circumference ratio, and compared this with standard ultrasonographic methods of growth assessment. STUDY DESIGN We prospectively studied 825 low-risk obstetric patients and 250 patients having risk factors for fetal macrosomia (n = 92) or growth retardation (n = 158). Measured fetal parameters included the biparietal diameter, head circumference, transverse cerebellar diameter, abdominal circumference, and femur length. The estimated fetal weight, head circumference/abdominal circumference, cerebellar diameter/abdominal circumference, and femur length/abdominal circumference ratios were calculated. Reference curves for these parameters were created from a cross-sectional analysis of the low-risk group. Univariate analysis was used to determine the sensitivity, specificity, predictive values, and odds ratios of each individual parameter in identifying a small- or large-for-gestational-age infant. A multivariate logistic regression model with a variable selection procedure was then used to determine whether significance remained when we controlled for other parameters. RESULTS Within the low-risk group, the transverse cerebellar/abdominal circumference ratio was gestational age independent between 14 and 42 weeks with a mean of 13.68 +/- 0.96. A value exceeding 2 SD of the mean was significantly associated with birth or a small-for-gestational-age infant, being abnormal in 98% and 71% of asymmetrically and symmetrically growth-retarded infants, respectively. Significance was maintained in the multivariate regression model. The ratio was not helpful in detecting the large-for-gestational-age infant. CONCLUSION The fetal transverse cerebellar diameter/abdominal circumference ratio is an accurate, gestational age-independent method of identifying the small-for-gestational-age but not the large-for-gestational-age infant.

Univariate analysis of dichotomous or ordinal data from twin pairs: a simulation study comparing structural equation modeling and logistic regression.

The univariate analysis of categorical twin data can be performed using either structural equation modeling (SEM) or logistic regression. This paper presents a comparison between these two methods using a simulation study. Dichotomous and ordinal (three category) twin data are simulated under two different sample sizes (1,000 and 2,000 twin pairs) and according to different additive genetic and common environmental models of phenotypic variation. The two methods are found to be generally comparable in their ability to detect a “correct” model under the specifications of the simulation. Both methods lack power to detect the right model for dichotomous data when the additive genetic effect is low (between 10 and 20%) or medium (between 30 and 40%); the ordinal data simulations produce similar results except for the additive genetic model with medium or high heritability. Neither method could adequately detect a correct model that included a modest common environmental effect (20%) even when the additive genetic effect was large and the sample size included 2,000 twin pairs. The SEM method was found to have better power than logistic regression when there is a medium (30%) or high (50%) additive genetic effect and a modest common environmental effect. Conversely, logistic regression performed better than SEM in correctly detecting additive genetic effects with simulated ordinal data (for both 1,000 and 2,000 pairs) that did not contain modest common environmental effects; in this case the SEM method incorrectly detected a common environmental effect that was not present.

The menstrual cycle: relations of biophysical and hormonal determinations in normal women of reproductive age.

Appropriate relationships between circulating levels of 17 beta-E2 and P are necessary for normal endometrial development and blastocyst implantation. The aim of this study was to relate biophysical and biochemical measurements obtained during the menstrual cycle of six healthy women in 25 menstrual cycles. One hundred eighteen vaginosonographic determinations of the endometrial thickness together with serum E2 and P assays were performed at 5-day intervals. The three parameters studied were standardized by the formula: observation minus mean determination for that parameter divided by the standard deviation of that parameter. Using this common unit, the physiological relations between ultrasonographically determined endometrial thickness, E2, and P were readily seen.