Charles J. Cooper

A coordinating center in a clinical trial: The hypertension detection and followup program

Multicenter clinical trials are often larger and more complex than other methods of clinical inquiry. They tend to involve a number of research or clinical centers and several formal committees. In many of these trials a coordinating center is one of the participating organizational units. This article describes one such coordinating center, that of the Hypertension Detection and Follow-up Program (HDFP). In 1971 the HDFP Coordinating Center was established to assist in planning and implementing this National Heart, Lung, and Blood Institute (NHLBI)-sponsored, multicenter, community-based, randomized, controlled clinical trial. The HDFP Coordinating Center is a large, intricate organization comprised of personnel who perform a wide variety of functions. From 1972 to 1979 it supervised the adherence to a common protocol among the cooperating centers and reported the Programs progress to the various monitoring and review committees, the Steering Committee, and the NHLBI Program Office. The Program screened approximately 159,000 persons ages 30 to 69 years, identifying and following 10,940 hypertensive participants. It has been the responsibility of this Coordinating Center to institute, coordinate, and monitor the data-gathering activities of the study as a whole and to process, store, and analyze the large, multifaceted set of data that were collected.

Acute occupational injury among adolescent farmworkers from South Texas

Purpose This combined cross-sectional/cohort study addressed research gaps by estimating the rate of non-fatal occupational injury and identifying potential determinants among a population of adolescent farmworkers who are largely Hispanic and migrant. Methods The cohort included 410 farmworkers (aged 13–19 years) attending high school in South Texas along the border with Mexico. Data collection involved a self-administered, Web-based survey that solicited information on demographics, farm work variables including person-time at risk, occupational injury, health status and health risk behaviours. Cox regression was used to identify potential risk factors for non-fatal injury events experienced during a 9-month recall period. Results Depending on the definition of injury, the rate of non-fatal injury ranged from 27.0–73.6/100 full time equivalents. Variables with an increased and statistically significant HR in an adjusted Cox model included: age groups <15 years-old (5.82) and 16 years-old (4.47), usually sleeping <8 h during the week (2.10), feeling tense, stressed or anxious sometimes/often (2.25), not watching TV (2.65), working around ditches (2.01) and detasseling (2.70). Conclusions The high observed rates of non-fatal injury combined with the potential negative consequences and cost of these injuries signifies a compelling need for injury prevention efforts targeting adolescent, Hispanic, farmworkers.

Two-compartment Markov regression analysis

This paper presents a computer program for estimating transition rates between states in a two-compartment Markov process, where the rates are functions of covariates. Parameters are estimated by the method of maximum likelihood using the Newton-Raphson iterative procedure. The program provides statistics for testing hypotheses concerning regression coefficients and calculates observed versus expected values in order to assess the fit of the model to the data.

Cardiovascular Disease Risk Factors in Hispanic Adolescents in South Texas.

Objectives Despite a national crisis of increased prevalence of obesity and type 2 diabetes mellitus in adolescents, especially among Hispanics, there is a paucity of data on health indicators among farmworker adolescents and their peers. The main aim of this study was to estimate the prevalence of cardiovascular disease risk factors in a population of Hispanic adolescent students in south Texas. The study also aimed to compare the prevalence of these risk factors between students enrolled in the Migrant Education Program (MEP) and other students, and between boys and girls. Methods In partnership with the Weslaco (Texas) Independent School District and the Migrant Education Department, a cohort study was conducted from 2007 to 2010 to estimate the prevalence of overall obesity (body mass index ≥85th percentile for age and sex), abdominal obesity (waist circumference ≥75th percentile for age, sex, and ethnicity), acanthosis nigricans (AN), and high blood pressure (HBP; ≥90th percentile for age, height, and sex or systolic/diastolic BP ≥120/80 mm Hg) among MEP students compared with other students from two south Texas high schools. Multilevel logistic regression was used to assess the relation between sex and our main outcomes of interest while accounting for within-school nesting of participants. Results Among 628 sampled students, 508 (80.9%) completed the consent procedure and participated in the study. Of these, 257 were MEP students and 251 were non-MEP peers. Approximately 96.7% of participants were Hispanic and 50.0% were boys. Analyses of data across the years comparing MEP students and non-MEP students show an average prevalence of 44.8% versus 47.7% for overall obesity, 43.2% versus 43.7% for abdominal obesity, 24.7% versus 24.7% for AN, and 29.2% versus 32.8% for HBP. Across recruitment and follow-up years, the prevalence of overall obesity, abdominal obesity, and HBP was 1.3 to 1.5, 1.2 to 1.8, and 2.9 to 4.6 times higher in boys than in girls, respectively. In contrast, the prevalence of AN varied little by sex. Conclusions The high prevalence of cardiovascular risk factors in both groups suggests a compelling need for comprehensive, culturally targeted interventions to prevent future cardiovascular diseases in these high-risk Hispanic adolescents, especially among boys. There were not, however, substantial differences between MEP students and other students. These findings also support the feasibility of conducting future epidemiologic studies among adolescent farmworkers and their families, as well as culturally appropriate school or community-based interventions.