American journal of epidemiology
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Epidemiologists have utilized several health care systems with large numbers of enrollees and centralized databases to achieve their research aims. Although containing many of the features that have made certain health care systems valuable to the conduct of epidemiologic research, the US Department of Veterans Affairs (VA) medical care system has not been well utilized by epidemiologists. ⋯ Also, VA leadership has demonstrated an interest in the promotion of epidemiologic research by initiating several new programs, including the creation of three Epidemiologic Research and Information Centers (ERICs) to foster VA epidemiologic research, and announcing a program to support investigator-initiated epidemiologic research projects with VA funding. Epidemiologists with interests in medical problems that afflict veterans should consider partnerships with VA investigators to achieve their research aims.
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Comparative Study
Measles epidemic in Romania, 1996-1998: assessment of vaccine effectiveness by case-control and cohort studies.
A measles epidemic occurred in Romania with 32,915 cases and 21 deaths reported between November 1996 and June 1998, despite high vaccination coverage since the early 1980s. Most cases were unvaccinated children aged <2 years and vaccinated school-aged children. A case-control study among preschool children and a cohort study among primary-school children were conducted to estimate effectiveness of Romanian-produced measles vaccine, and to evaluate age at vaccination and waning immunity as risk factors for vaccine failure. ⋯ Waning immunity was not identified as a risk factor since vaccine effectiveness was similar for children vaccinated 6-8, 9-11, and 12-14 years in the past. Because specific groups were not at risk for vaccine failure, an immunization campaign that targets all school-aged children who lack two doses may be an effective strategy for preventing outbreaks. A mass campaign followed by increased first-dose coverage should provide the population immunity required to interrupt indigenous measles virus transmission in Romania.
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The propensity score is the conditional probability of exposure to a treatment given observed covariates. In a cohort study, matching or stratifying treated and control subjects on a single variable, the propensity score, tends to balance all of the observed covariates; however, unlike random assignment of treatments, the propensity score may not also balance unobserved covariates. The authors review the uses and limitations of propensity scores and provide a brief outline of associated statistical theory. They also present a new result of using propensity scores in case-cohort studies.
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Randomized Controlled Trial Clinical Trial
Application of computer-assisted interviews to sexual behavior research.
Collection of sensitive data with the use of video-enhanced, computer-assisted, self-administered interviews (V-CASI) has the potential to reduce interview bias and improve the validity of the study. The purpose of this study was to compare responses to sensitive questions elicited by V-CASI and by face-to-face interview (FTFI) methods. Women attending a New Orleans, Louisiana, public family planning or sexually transmitted disease clinic from July 1995 to July 1996, diagnosed with a Chlamydia trachomatis infection responded to eight close-ended behavioral questions (four socially undesirable, two socially desirable, and two neutral behaviors) using both FTFI and V-CASI techniques in a randomized crossover design. ⋯ Women who reported a socially undesirable behavior in V-CASI (i.e., more than two sex partners and infrequent condom usage) were more likely to have a discrepant response. Utilization of the same logistic regression model to predict condom use yielded different results when data from V-CASI were used compared with data from FTFI. The V-CASI technique can reduce social desirability bias and improve validity in research requiring information on sensitive sexual behaviors.
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In a prospective cohort study, associations of resting heart rate with risk of coronary, cardiovascular disease, cancer, and all-cause mortality in age-specific cohorts of black and white men and women were examined over 22 years of follow-up. Participants were employees from 84 companies and organizations in the Chicago, Illinois, area who volunteered for a screening examination. Participants included 9,706 men aged 18-39 years, 7,760 men aged 40-59 years, 1,321 men aged 60-74 years, 6,928 women aged 18-39 years, 6,915 women aged 40-59 years, and 1,151 women aged 60-74 years at the baseline examination in 1967-1973. ⋯ All-cause mortality was associated with higher heart rate in men aged 18-39 years (RR = 1.11, 95% CI 1.01-1.20), men aged 40-59 years (RR = 1.16, 95% CI 1.11-1.21), and women aged 40-59 years (RR = 1.20, 95% CI 1.13-1.27). Heart rate was not associated with mortality in women aged 18-39 years. In summary, heart rate was a risk factor for mortality from coronary disease, all cardiovascular diseases, and all causes in younger men and in middle-aged men and women, and for cancer mortality in middle-aged men and women.