Journal of clinical epidemiology
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In the epidemiologic literature, one finds three criteria for confounding, which we will call the classical (marginal), operational (change-in-estimate) and conditional criteria. We define mavericks to be covariates that satisfy the operational criterion, but not the classical criterion. We present what is known about the problems of mavericks for estimating odds ratios and clarify the interpretation of odds ratios. Key results are: (1) omitting mavericks biases odds ratios towards 1; (2) omitting mavericks cannot artificially introduce an effect in contrast to omitting classical confounders; (3) the operational criterion for confounding corresponds to the conditional criterion when estimating odds ratios, but for relative risks, there are no mavericks (i.e. the classical and operational criterion correspond); and (4) the interpretation of odds ratios obtained from standard methods is that of comparing proportions, not of individual risk.
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The known risk factors of atherosclerotic diseases may be involved in the development of a subarachnoid hemorrhage. We studied the morbidity and mortality due to subarachnoid hemorrhage among 42,862 men and women aged 20-69 years who had participated in a large health survey in Finland. During a mean follow-up of 12 years, 102 non-fatal and 85 fatal cases of subarachnoid hemorrhage were observed. ⋯ The age-adjusted relative risks of subarachnoid hemorrhage for lean, hypertensive smokers were 18.3 (95% confidence interval (CI), 7.8-42.7) among women and 6.7 (95% CI, 2.3-19.7) among men as compared to the risk among subjects without these risk factors. We conclude that modifiable risk factors are predictive of subarachnoid hemorrhage, for which reason subarachnoid hemorrhage may in part be preventable. Leanness combined with arterial hypertension and/or smoking, in particular, poses a substantially elevated risk.
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Comparative Study
Pharmacoepidemiology in pre-approval clinical trial safety monitoring.
Applications of pharmacoepidemiology to the pre-approval safety monitoring of investigational drugs are examined and compared with the post-approval applications. Pre-approval epidemiologic assessments of drug safety can complement clinical assessments of rare, serious adverse events occurring in open label uncontrolled clinical trials. ⋯ Advance planning of historical data sources is essential as is an effective clinical trial data management system. Implications for methodologic research and for drug development are discussed.
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We present the first prevalence study of specific headache entities using the operational diagnostic criteria of the International Headache Society. One thousand 25-64 year old men and women, who lived in the western part of Copenhagen County were randomly drawn from the Danish National Central Person Registry. All subjects were invited to a general health examination focusing on headache and including: a self-administered questionnaire concerning sociodemographic variables, a structured headache interview and a general physical and neurological examination. ⋯ Differences according to sex were significant with a male: female ratio of 1:3 in migraine, and 4:5 in tension-type headache. The prevalence of tension-type headache decreased with increasing age, whereas migraine showed no correlation to age within the studied age interval. Headache disorders are extremely prevalent and represent a major health problem, which merits increased attention.
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In order to study the possible association between socioeconomic status (SES) and critical care mortality, we examined a cohort of 847 patients over 14 years of age, as they were consecutively admitted to three general intensive care units (ICUs). The patients with low SES (social classes IV and V according to the British Registrar General's classification) were older (62.0 v 58.5 years old, p less than 0.0001) and showed a higher ICU mortality (odds ratio (OR) = 1.61, p = 0.0204) and severity of illness on admission (mean Simplified Acute Physiology Score [SAPS] 9.9 vs 8.7, p = 0.0002) than patients with high SES (social classes I-III). The initial severity of illness differential was detected both in patients admitted from the emergency area and in patients admitted from the general hospitalization ward, suggesting the existence of some kind of preselection procedure related to the SES of the patient. ⋯ We conclude that there is an inverse relationship between SES and ICU mortality. The mortality excess in the low SES patients is largely accounted for by the covariates of the low SES (especially their high age and severity of illness on admission). There is no evidence of a different relative therapeutic effort according to the SES.