American journal of epidemiology
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In observational studies on cancer patients, progression of performance status over time can be described by using a multistate model in which state-to-state transitions represent changes in a patient's health condition. Although a patient experiences transitions in continuous time, assessments on the patient are often made at irregularly spaced time points. In this paper, the authors formulate a Markov 4-state model for examining longitudinal data on performance status collected under intermittent observation. ⋯ The authors extend the model to estimate the predicted probability of reaching the absorbing state, death, over various time intervals. The authors also illustrate what happens to the estimated transition intensities if the true observational scheme is overlooked. Methods for multistate analysis should be used by epidemiologists, since they prove particularly useful for examining the complexities of disease processes.
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Multicenter Study
Similar relation of age and height to lung function among Whites, African Americans, and Hispanics.
Current guidelines recommend separate spirometry reference equations for whites, African Americans, and Mexican Americans, but the justification for this recommendation is controversial. The authors examined the statistical justification for race/ethnic-specific reference equations in adults in the Third National Health and Nutrition Examination Survey (1988-1994) and the Multi-Ethnic Study of Atherosclerosis Lung Study (2000-2006). Spirometry was measured following American Thoracic Society guidelines. "Statistical justification" was defined as the presence of effect modification by race/ethnicity among never-smoking participants without respiratory disease or symptoms and was tested with interaction terms for race/ethnicity (× age and height) in regression models. ⋯ Findings were similar in the Multi-Ethnic Study of Atherosclerosis Lung Study. The associations of age and height with lung function are similar across the 3 major US race/ethnic groups. Multiethnic rather than race/ethnic-specific spirometry reference equations are applicable for the US population.
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Although the September 11, 2001, terrorist attacks were the largest human-made disaster in US history, there is little extant research documenting the attacks' consequences among those most directly affected, that is, persons who were in the World Trade Center towers. Data from a cross-sectional survey conducted 2-3 years after the attacks ascertained the prevalence of long-term, disaster-related posttraumatic stress symptoms and probable posttraumatic stress disorder (PTSD) in 3,271 civilians who evacuated World Trade Center towers 1 and 2. Overall, 95.6% of survivors reported at least 1 current posttraumatic stress symptom. ⋯ Working for an employer that sustained fatalities also increased risk. Each addition of an experience of direct exposure resulted in a 2-fold increase in the risk of PTSD (odds ratio = 2.09, 95% confidence interval: 1.84, 2.36). Identification of these risk factors may be useful when screening survivors of large-scale terrorist events for long-term psychological sequelae.