Understanding immortal time bias in observational cohort studies
نویسندگان
چکیده
منابع مشابه
Immortal time bias in observational studies of drug effects in pregnancy.
BACKGROUND The use of decongestants during the second or third trimesters of pregnancy has been associated with a decreased risk of preterm delivery in two observational studies. This effect may have been subject to immortal time bias, a bias arising from the improper classification of exposure during follow-up. We illustrate this bias by repeating the studies using a different data source. M...
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In the March 2007 issue of JASN, Hemmelgarn et al.1 reported a 50% reduction in the risk for all-cause mortality for patients who had chronic kidney disease (CKD) and attended multidisciplinary care (MDC) clinics compared with those who received usual care. Their survival curves showed a clear divergence in rates of death between the two groups in the first 6 mo of follow-up. We suggest that it...
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T he randomized clinical trial is a well established and frequently used study design and is generally accepted as the gold standard (1). Nevertheless, many questions can only be answered with epidemiological observational studies, such as the influence of cigarette consumption on the development of lung cancer (2), the effects of sport, nutrition and overweight on cardiovascular diseases (3), ...
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Immortal time is a span of cohort follow-up during which, because of exposure definition, the outcome under study could not occur. Bias from immortal time was first identified in the 1970s in epidemiology in the context of cohort studies of the survival benefit of heart transplantation. It recently resurfaced in pharmacoepidemiology, with several observational studies reporting that various med...
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ژورنال
عنوان ژورنال: Anaesthesia
سال: 2012
ISSN: 0003-2409
DOI: 10.1111/anae.12120