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Biomedical subjects

Trivellore E Raghunathan

Publications and source records attributed to Trivellore E Raghunathan.

At least 19 recordsLinked to original sources
PubMed2007

Estimation of the proportion of overweight individuals in small areas - a robust extension of the Fay-Herriot model.

Hierarchical model such as Fay-Herriot (FH) model is often used in small area estimation. The method might perform well overall but is vulnerable to outliers. We propose a robust extension of the FH model by assuming the area random effects follow a t distribution with an unknown degrees-of-freedom parameter. The inferences are constructed using a Bayesian framework. Monte Carlo Markov Chain (MCMC) such as Gibbs sampling and Metropolis-Hastings acceptance and rejection algorithms are used to obtain the joint posterior distribution of model parameters. The procedure is used to estimate the county-level proportion of overweight individuals from the 2003 public-use Behavioral Risk Factor Surveillance System (BRFSS) data. We also discuss two approaches for identifying outliers in the context of this application.

Adolescent↗
PubMed2006

Association of insulin resistance with distance to wealthy areas: the multi-ethnic study of atherosclerosis.

Little is known about environmental determinants of type 2 diabetes. The authors hypothesized that insulin resistance is positively related to distance to a wealthy area and to local neighborhood poverty. Data were derived from The Multi-Ethnic Study of Atherosclerosis, a study of adults aged 45-84 years in six US locales, and the 2000 US Census. The homeostasis model assessment (HOMA) index was used to measure insulin resistance. Linear regression was used to estimate associations between area characteristics and insulin resistance after adjustment for age, sex, income, education, and race/ethnicity and for the potential mediators diet, physical activity, and body mass index (n = 4,821). Among persons not treated for diabetes, distance to a wealthy area was associated with HOMA independent of local poverty and person-level covariates: per 4.4-km change, the relative increase in HOMA was 13% (95% confidence interval: 7%, 19%), similar to the effect of a body mass index increase of 1.7 kg/m(2) on HOMA. This association was reduced after adjustment for physical activity, diet, and body mass index (relative increase = 9%, 95% confidence interval: 3%, 15%). Local neighborhood poverty was also positively, but more weakly associated with insulin resistance, with no association after adjustment for race/ethnicity. This study shows that proximity to resources in high-income areas is related to insulin resistance.

Aged↗
PubMed2006

Socioeconomic and psychosocial exposures across the life course and binge drinking in adulthood: population-based study.

Despite recognition of the health risks of binge drinking, its life-course precursors have not been widely examined. Data from the Kuopio Ischemic Heart Disease Risk Factor Study (1984-1989) were used to investigate the association between socioeconomic and psychosocial exposures across the life course and binge drinking in a population-based sample of 2,316 middle-aged men. Binge drinking was defined as drinking at least four bottles of beer, one bottle of wine, one bottle of strong wine, or six servings of spirits on a single occasion. A composite indicator of childhood socioeconomic position was based on parental education, occupation, and number of rooms and divided into tertiles. Low childhood socioeconomic position increased the odds of binge drinking (odds ratio = 1.70, 95% confidence interval: 1.26, 2.31) when other early life exposures were adjusted. Additional adjustment of adult socioeconomic and psychosocial factors attenuated the odds of bingeing associated with low childhood socioeconomic position (odds ratio = 1.29, 95% confidence interval: 0.93, 1.79). Adult socioeconomic conditions, marital status, hostility, and organizational membership were independently associated with bingeing. This study shows that both early and later life characteristics including socioeconomic conditions and adult psychosocial factors contribute to adult binge drinking in this population, but the effects of adult characteristics are stronger.

Adult↗
PubMed2006

Are antiseptic-coated central venous catheters effective in a real-world setting?

BACKGROUND: Catheter-related bloodstream infections are common, costly, and morbid. Randomized controlled trials indicate that antiseptic-coated central venous catheters reduce infection rates. OBJECTIVE: To assess the clinical and economic effectiveness of antiseptic-coated catheters for critically ill patients in a real-world setting. METHODS: Central venous catheters coated with chlorhexidine/silver-sulfadiazene were introduced in all patients requiring central venous access in adult intensive care units at the University of Michigan Health System, a large, tertiary care teaching hospital. A pretest-posttest cohort design measured the primary outcome of catheter-related bloodstream infection rate, comparing the 2 years prior to the intervention with the 2 years following the intervention. We also evaluated cost-effectiveness and changes in vancomycin use. RESULTS: The intervention was associated with a 4% per month relative reduction in the incidence of catheter-related bloodstream infection, after controlling for the effects of time. Overall, a 35% relative risk reduction (P < .0003) in the catheter-related bloodstream infection rate occurred in the posttest phase. The use of antiseptic-coated catheters reduced costs more than $100,000 annually. Vancomycin use was less in units in which antiseptic catheters were used compared with wards in which these catheters were not used. CONCLUSION: Antiseptic-coated catheters appear to be clinically effective and economically efficient in a real-world setting.

Anti-Bacterial Agents↗
PubMed2006

The role of personality characteristics in young adult driving.

BACKGROUND: Motor vehicle injury is the major cause of mortality among young adults. Information about the individual characteristics of those who drive dangerously could enhance traffic safety programs. The goal of this research was to examine the association between various personality-related characteristics and risky driving behaviors. METHODS: Young adults in Michigan, USA (n = 5,362) were surveyed by telephone regarding several personality factors (risk-taking, hostility, aggression, tolerance of deviance, achievement expectations) and driving behaviors (competitive driving, risk-taking driving, high-risk driving, aggressive driving, and drink/driving). Michigan driver records were obtained to examine offenses, serious offenses, driving offense points, crashes and serious crashes in the three pre-interview years. Multivariate regression analyses, adjusting for age, race, and marital status were conducted separately by sex to identify personality factors related to driving. RESULTS: For men and women, greater risk-taking propensity, physical/verbal hostility, aggression, and tolerance of deviance were significant predictors of a competitive attitude toward driving, risk-taking driving, high-risk driving, driving aggression, and drink/driving. Greater risk-taking propensity, physical/verbal hostility, aggression, and to a small degree, expectations for achievement predicted higher numbers of offenses, serious offenses, and points. CONCLUSION: Traffic safety policies and programs could be enhanced through recognition of the role personality factors play in driving behavior and the incorporation of this knowledge into the design and implementation of interventions that modify the behaviors associated with them.

Accidents, Traffic↗
PubMed2006

Gender differences among young drivers in the association between high-risk driving and substance use/environmental influences.

OBJECTIVE: The primary aim of this article is to assess young drivers' gender differences in the associations between substance use/environmental influences and high-risk driving behavior. METHOD: We determine the association of 12th-grade self-reported substance use/ environmental influences with high-risk driving behavior as quantified by the number of offenses, serious offenses, crashes, and single-vehicle crashes on state driving records during subjects' (N = 3,607; 51% male) first 4 years of licensure. RESULTS: The associations between high-risk driving and substance use/environmental influences were generally stronger among women than among men. When matched by substance-use profiles, women had fewer risky-driving incidents than men. CONCLUSIONS: The results indicate that young women who exhibit high-risk driving behavior deviate more from the general population of young women with respect to alcohol use, alcohol misuse, and marijuana use than high-risk-driving young men differ from other young men. In addition, findings indicate that even if young men and women were to eventually have equal levels of substance use, women would likely retain their lower-risk driving profiles. These findings suggest the need for (1) future research to understand the differential associations, and (2) prevention programs that consider these gender differences.

Accidents, Traffic↗
PubMed2005

Education, income, occupation, and the 34-year incidence (1965-99) of Type 2 diabetes in the Alameda County Study.

BACKGROUND: Lower socioeconomic position (SEP) is related to higher prevalence of Type 2 diabetes, yet little is known about the relationship of SEP with incident diabetes. METHODS: The association between SEP, measured by self-reported education, income, and occupation, and Type 2 diabetes incidence was examined in a community sample of 6147 diabetes-free adults from Alameda County, CA. Cox proportional hazards models estimated the effect of baseline (1965) and time-dependent (value changes over time) measures of SEP on incident diabetes over a 34-year study period (1965-99). Demographic confounders (age, gender, race, and marital status) and potential components of the causal pathway (physical inactivity, smoking, alcohol consumption, body composition, hypertension, depression, and health care access) were included as fixed or time-dependent covariates. RESULTS: Education, income, and occupation were associated with increased diabetes risk in unadjusted models. In baseline models adjusted for demographics, respondents with <12 years of education had 50% excess risk compared with those with more education [hazard ratio (HR) = 1.5, 95% confidence interval (95% CI) 1.11-2.04], but income and occupation were no longer significantly associated with increased risk. Further adjustment minimized the significance of all associations. Time-dependent effects were consistently elevated for low education and male blue-collar occupation, but non-significant after full adjustment (HR = 1.1, 95% CI 0.79-1.47 and HR = 1.3, 95% CI 0.91-1.89, respectively). CONCLUSIONS: Socioeconomic disadvantage, especially with low educational attainment, is a significant predictor of incident Type 2 diabetes, although associations were largely eliminated after covariate adjustment. Obesity and overweight appear to mediate these associations.

Adolescent↗
PubMed2005

Race/ethnicity, life-course socioeconomic position, and body weight trajectories over 34 years: the Alameda County Study.

OBJECTIVES: We investigated whether race differences in weight gain over 34 years were because of socioeconomic position (SEP) and psychosocial and behavioral factors (physical activity, cigarette smoking, alcohol consumption, depression, marital status, number of children). We used a life-course approach to SEP with 4 measures of SEP (childhood SEP, education, occupation, income) and a cumulative measure of SEP. METHODS: We used mixed models and data collected from the Alameda County Study to examine the association between race and weight change slopes and baseline weight in men (n=1186) and women (n=1375) aged 17 to 40 years at baseline (in 1965). RESULTS: All subjects gained weight over time. African American women weighed 4.96 kg (P < .001) more at baseline and gained 0.10 kg/year (P = .043) more weight than White women. Black men weighed 2.41 kg (P = .006) more at baseline but did not gain more weight than White men. The association of race with weight gain in women was largely because of cumulative SEP score. CONCLUSIONS: Interventions to prevent overweight and obesity should begin early in life and target the socioeconomically disadvantaged.

Adolescent↗
PubMed2005

Modeling cortisol rhythms in a population-based study.

The aim of these analyses was to develop and describe easily implementable, yet information rich, approaches for analysis of the temporal profile of cortisol in human populations. A typical waking profile of cortisol in a sample of women aged 15-44 was parameterized by a piecewise linear regression model, implemented as a mixed model to accommodate repeated observations among individuals. The model was extended to distinguish characteristic cortisol profiles of obese women from those of non-obese women. Sharp inflection points for the diurnal profile of cortisol were noted at 30 and 75 min past awakening. Obese women showed a slight tendency to have a less sharply rising and declining response to awakening than non-obese women.

Adolescent↗
PubMed2005

The health of poor women under welfare reform.

OBJECTIVES: We compared the health of single mothers affected by welfare reform with the health of a nationally representative sample of women to document the prevalence of poor health as single mothers experience the effects of welfare reform. METHODS: We compared risk factors and measures of health among women randomly sampled from the welfare rolls with similar data from a nationally representative sample of women. RESULTS: Women in our welfare recipient sample had higher rates of elevated glycosylated hemoglobin (> or = 6%; prevalence ratio [PR]=4.87; 95% confidence interval [CI]=2.69, 7.04), hypertension (systole > or = 140 or diastole > or = 90; PR=2.36; 95% CI = 1.47, 3.24), high body mass index ( > or = 30; PR = 1.78; 95% CI = 1.49, 2.08), and high-density lipoprotein cholesterol (< or = 35 mg/dL; PR=1.91; 95% CI=1.17, 2.65); lower peak expiratory flow; and less physical functioning. Current smoking rates were higher (PR = 1.85; 95% CI = 1.50, 2.19) and smoking cessation rates were lower (PR=0.62; 95% CI=0.37, 0.86) than in the national sample. CONCLUSIONS: Current and former welfare recipients bear a substantial burden of illness. Further studies are necessary to interpret our findings of worsened health in the wake of welfare reform.

Adult↗
PubMed2004

Incidence of out-of-hospital cardiac arrest.

Estimates of the incidence of out-of-hospital primary cardiac arrest (CA) have typically relied solely upon emergency medical service or death certificate records and have not investigated incidence in clinical subgroups. Overall and temporal patterns of CA incidence were investigated in clinically defined groups using systematic methods to ascertain CA. Estimates of incidence were derived from a population-based case-control study in a large health plan from 1986 to 1994. Subjects were enrollees aged 50 to 79 years who had had CA (n = 1,275). A stratified random sample of enrollees who had not had CA was used to estimate the population at risk with various clinical characteristics (n = 2,323). Poisson's regression was used to estimate incidence overall and for 3-year time periods (1986 to 1988, 1989 to 1991, and 1992 to 1994). The overall CA incidence was 1.89/1,000 subject-years and varied up to 30-fold across clinical subgroups. For example, incidence was 5.98/1,000 subject-years in subjects with any clinically recognized heart disease compared with 0.82/1,000 subject-years in subjects without heart disease. In subgroups with heart disease, incidence was 13.69/1,000 subject-years in subjects with prior myocardial infarction and 21.87/1,000 subject-years in subjects with heart failure. Risk decreased by 20% from the initial to the final time period, with a greater decrease observed in those with (25%) compared with those without (12%) clinical heart disease. Thus, CA incidence varied considerably across clinical groups. The results provide insights regarding absolute and population-attributable risk in clinically defined subgroups, information that may aid strategies aimed at reducing mortality from CA.

Age Factors↗
PubMed2004

An extended general location model for causal inferences from data subject to noncompliance and missing values.

Noncompliance is a common problem in experiments involving randomized assignment of treatments, and standard analyses based on intention-to-treat or treatment received have limitations. An attractive alternative is to estimate the Complier-Average Causal Effect (CACE), which is the average treatment effect for the subpopulation of subjects who would comply under either treatment (Angrist, Imbens, and Rubin, 1996, Journal of American Statistical Association 91, 444-472). We propose an extended general location model to estimate the CACE from data with noncompliance and missing data in the outcome and in baseline covariates. Models for both continuous and categorical outcomes and ignorable and latent ignorable (Frangakis and Rubin, 1999, Biometrika 86, 365-379) missing-data mechanisms are developed. Inferences for the models are based on the EM algorithm and Bayesian MCMC methods. We present results from simulations that investigate sensitivity to model assumptions and the influence of missing-data mechanism. We also apply the method to the data from a job search intervention for unemployed workers.

Algorithms↗
PubMed2004

What do we do with missing data? Some options for analysis of incomplete data.

Missing data are a pervasive problem in many public health investigations. The standard approach is to restrict the analysis to subjects with complete data on the variables involved in the analysis. Estimates from such analysis can be biased, especially if the subjects who are included in the analysis are systematically different from those who were excluded in terms of one or more key variables. Severity of bias in the estimates is illustrated through a simulation study in a logistic regression setting. This article reviews three approaches for analyzing incomplete data. The first approach involves weighting subjects who are included in the analysis to compensate for those who were excluded because of missing values. The second approach is based on multiple imputation where missing values are replaced by two or more plausible values. The final approach is based on constructing the likelihood based on the incomplete observed data. The same logistic regression example is used to illustrate the basic concepts and methodology. Some software packages for analyzing incomplete data are described.

Data Interpretation, Statistical↗
PubMed2003

Digoxin therapy and the risk of primary cardiac arrest in patients with congestive heart failure: effect of mild-moderate renal impairment.

BACKGROUND AND OBJECTIVE: The cardiac safety of digoxin therapy for congestive heart failure (CHF) is a source of concern, especially among those with renal impairment. METHODS: Using a case-control design, we examined the risk of primary cardiac arrest (PCA) associated with digoxin therapy within three levels of renal function. RESULTS: After adjustment for other clinical characteristics, digoxin therapy for CHF was not associated with an increased risk of PCA [odds ratio (OR)=0.97, 95% confidence interval (CI) 0.59-1.62] among patients with normal renal function (serum creatinine </=1.1 mg/dL). In contrast, digoxin therapy was associated with a modest increase in risk (OR=1.58, CI 0.89-2.80) among patients with mild renal impairment (serum creatinine=1.2-1.4 mg/dL); and a twofold increase in risk (OR=2.39, CI 1.37-4.18) among patients with moderate renal impairment (serum creatinine=1.5-3.5 mg/dL). CONCLUSIONS: These findings suggest that the risks of digoxin may offset the benefits among patients with moderately impaired renal function, but not among patients with normal renal function.

Aged↗
PubMed2003

Examining trajectories of adolescent risk factors as predictors of subsequent high-risk driving behavior.

PURPOSE: To examine the effects on early high-risk driving behavior of changes over time (trajectories) in adolescent alcohol use, friends' support for drinking, susceptibility to peer pressure, and tolerance of deviance. METHODS: Statewide driving data were obtained for 4813 subjects who had completed at least two previous school-based questionnaires. The self-administered questionnaire data provided predictor measures from 5th through 10th grades. Trajectory information on predictor measures was summarized using each measure's slope over time and level at the 10th grade data collection (last value). Regression models used serious offenses, alcohol-related offenses, serious crashes, and alcohol-related crashes as outcomes, trajectory measures as predictors, and produced parameter estimates adjusted for demographic measures. Probabilities of having a serious offense or serious crash for five sample trajectories on each measure were obtained from the estimated regression models. RESULTS: All four predictor measures were important, particularly in predicting serious offenses, alcohol-related offenses, and alcohol-related crashes. The highest probabilities for young adult high-risk driving were found among those with consistently high or increasingly high trajectories of friends' support for drinking, susceptibility to peer pressure, and tolerance of deviance. CONCLUSIONS: Programs to prevent adolescent risk behavior should take into account environmental and personality influences. Prevention efforts need to emphasize preserving low levels, preventing increases, and promoting decreases over time of adolescent risk factors for unhealthy behaviors, such as high-risk driving.

Accidents, Traffic↗
PubMed2002

Inhaled beta-2 adrenergic receptor agonists and primary cardiac arrest.

PURPOSE: We sought to investigate if short-acting, inhaled beta2-adrenergic receptor agonists were associated with higher risk of primary cardiac arrest in patients with asthma or chronic obstructive pulmonary disease (COPD). SUBJECTS AND METHODS: We conducted a population-based study involving 454 patients enrolled in a health maintenance organization, aged 40 to 79 years, who had asthma or COPD and who experienced primary cardiac arrest during 1980 to 1994. We randomly selected 586 controls from strata of enrollees, defined by age, sex, calendar year, and prior heart disease. Medication use was assessed from computerized pharmacy data, and risk factors from medical record review. RESULTS: Use of inhaled beta-agonists was associated with a twofold increased risk of primary cardiac arrest (odds ratio [OR] = 1.9; 95% confidence interval [CI]: 1.1 to 3.3) among patients with asthma, but not among those with COPD (OR = 1.3; 95% CI: 0.6 to 2.7), after adjustment for risk factors. This association was observed only with use of two or more canisters of metered-dose, inhaled beta-agonists for 3 months, and when inhaled steroids were not used. CONCLUSION: These results support current guidelines recommending inhaled steroids as first-line asthma therapy.

Administration, Inhalation↗
PubMed2002

Use of multiple imputation to correct for nonresponse bias in a survey of urologic symptoms among African-American men.

The Flint Men's Health Study is an ongoing population-based study of African-American men designed to address questions related to prostate cancer and urologic symptoms. The initial phase of the study was conducted in 1996-1997 in two stages: an interviewer-administered survey followed by a clinical examination. The response rate in the clinical examination phase was 52%. Thus, some data were missing for clinical examination variables, diminishing the generalizability of the results to the general population. This paper is a case study demonstrating the application of multiple imputation to address important questions related to prostate cancer and urologic symptoms in a data set with missing values. On the basis of the observed clinical examination data, the American Urological Association Symptoms Score showed a surprising reduction in symptoms in the oldest age group, but after multiple imputation there was a monotonically increasing trend with age. It appeared that multiple imputation corrected for nonresponse bias associated with the observed data. For other outcome measures-namely, the age-adjusted 95th percentile of prostate-specific antigen level and the association between urologic symptoms and prostate volume-results from the observed data and the multiply imputed data were similar.

Adult↗