# epidemiology

**URL:** https://discourse.datamethods.org/c/topical/epi/60.md

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## [About the epidemiology category](https://discourse.datamethods.org/t/about-the-epidemiology-category/83)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 0

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Epidemiology, especially related to particular epidemiologic studies and study designs

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## [Sterilization Assurance Level (SAL) in medical device sterilization processes](https://discourse.datamethods.org/t/sterilization-assurance-level-sal-in-medical-device-sterilization-processes/28700)

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**Author:** [@Dmartins](https://discourse.datamethods.org/u/Dmartins)\
**Replies:** 0\
**Last updated:** [April 9, 2026, 4:49pm UTC](https://discourse.datamethods.org/t/sterilization-assurance-level-sal-in-medical-device-sterilization-processes/28700 "2026-04-09T16:49:54Z")

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I worked for 4.5 years as a medical device sterilization technician. In sterilization science we use a concept named Sterility Assurance Level (SAL) to ensure the safety of medical devices after sterilization. However, …

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## [Clustering in the denominator: non-independence of starts in racing fatality studies](https://discourse.datamethods.org/t/clustering-in-the-denominator-non-independence-of-starts-in-racing-fatality-studies/28662)

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**Author:** [@trumanfrancis](https://discourse.datamethods.org/u/trumanfrancis)\
**Replies:** 4\
**Last updated:** [March 31, 2026, 8:04am UTC](https://discourse.datamethods.org/t/clustering-in-the-denominator-non-independence-of-starts-in-racing-fatality-studies/28662 "2026-03-31T08:04:51Z")

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I’d appreciate the group’s thinking on a methodological question that arises in equine racing fatality epidemiology, though the underlying issue generalizes to any setting where a rare terminal outcome is modeled using r…

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## [Intermittent exposure variable in causal inference](https://discourse.datamethods.org/t/intermittent-exposure-variable-in-causal-inference/7144)

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**Author:** [@trumanfrancis](https://discourse.datamethods.org/u/trumanfrancis)\
**Replies:** 8\
**Last updated:** [November 2, 2023, 9:00pm UTC](https://discourse.datamethods.org/t/intermittent-exposure-variable-in-causal-inference/7144 "2023-11-02T21:00:25Z")

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I have been asked to assist in the design and analysis of an observational study where the exposure is the administration of a medication to racehorses (furosemide) and the outcome of interest is career length. That is …

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## [Healthy user bias with vaccines - positive or negative?](https://discourse.datamethods.org/t/healthy-user-bias-with-vaccines-positive-or-negative/6900)

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**Author:** [@tamas.ferenci](https://discourse.datamethods.org/u/tamas.ferenci)\
**Replies:** 1\
**Last updated:** [July 2, 2023, 9:42pm UTC](https://discourse.datamethods.org/t/healthy-user-bias-with-vaccines-positive-or-negative/6900 "2023-07-02T21:42:43Z")

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Consider the following two examples: UK reports the age-standardized all-cause mortality rate by COVID vaccination status, which sometimes reports significantly larger mortality for vaccinated people. This is of course…

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## [Re-using same Controls for different Subgroup Analyses](https://discourse.datamethods.org/t/re-using-same-controls-for-different-subgroup-analyses/6768)

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**Author:** [@mksp](https://discourse.datamethods.org/u/mksp)\
**Replies:** 4\
**Last updated:** [May 17, 2023, 12:45pm UTC](https://discourse.datamethods.org/t/re-using-same-controls-for-different-subgroup-analyses/6768 "2023-05-17T12:45:19Z")

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Dear Experts ! I need your opinion about a study design : For a study with 1500 cases (with many subgroups) i have (for logistical restrictions) only 300 controls. My questions (1) Is it acceptable to bootstrap contr…

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## [Could we calculate the adjusted proportion in Table 1?](https://discourse.datamethods.org/t/could-we-calculate-the-adjusted-proportion-in-table-1/6323)

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**Author:** [@JiaqiLi](https://discourse.datamethods.org/u/JiaqiLi)\
**Replies:** 8\
**Last updated:** [January 4, 2023, 12:58am UTC](https://discourse.datamethods.org/t/could-we-calculate-the-adjusted-proportion-in-table-1/6323 "2023-01-04T00:58:55Z")

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I found that several studies showed the adjusted baseline characteristics including proportion in Table 1. The adjusted means could be calculated by estimated marginal means (right?), but how could calculate the adjusted…

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## [How to calculate odds ratio per one standard deviation?](https://discourse.datamethods.org/t/how-to-calculate-odds-ratio-per-one-standard-deviation/6322)

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**Author:** [@JiaqiLi](https://discourse.datamethods.org/u/JiaqiLi)\
**Replies:** 4\
**Last updated:** [December 28, 2022, 9:10am UTC](https://discourse.datamethods.org/t/how-to-calculate-odds-ratio-per-one-standard-deviation/6322 "2022-12-28T09:10:53Z")

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I want to calcualte odds ratio per one standard deviation in my research. As far as I know, there are two methods. Which one method is right? Method 1: new\_var = old\_var / standard deviation of old\_var. Method 2: new\_…

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## [\# How to convert continuous relative risks per exposure unit ?](https://discourse.datamethods.org/t/how-to-convert-continuous-relative-risks-per-exposure-unit/5890)

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**Author:** [@Rataplan](https://discourse.datamethods.org/u/Rataplan)\
**Replies:** 1\
**Last updated:** [August 21, 2022, 8:18pm UTC](https://discourse.datamethods.org/t/how-to-convert-continuous-relative-risks-per-exposure-unit/5890 "2022-08-21T20:18:26Z")

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How to convert continuous relative risks per exposure unit ? If a study for example concludes that the relative risk of a cardiovascular event is 1.04 per 10 µg/m³ increase in NO2, how can I calculate the relative risk f…

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## [mRNA vaccine effectiveness matched case-control design](https://discourse.datamethods.org/t/mrna-vaccine-effectiveness-matched-case-control-design/5462)

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**Author:** [@s\_doi](https://discourse.datamethods.org/u/s_doi)\
**Replies:** 18\
**Last updated:** [July 14, 2022, 11:16pm UTC](https://discourse.datamethods.org/t/mrna-vaccine-effectiveness-matched-case-control-design/5462 "2022-07-14T23:16:59Z")

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We have created a preprint assessing over 400000 consecutive cases of COVID-19 using a hard endpoint - admission to ICU - to assess mRNA vaccine effectiveness. We got very different results from the main-stream papers in…

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## [Is it the numerator or denominator which explains variations of a ratio?](https://discourse.datamethods.org/t/is-it-the-numerator-or-denominator-which-explains-variations-of-a-ratio/5600)

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**Author:** [@marcusbendtsen](https://discourse.datamethods.org/u/marcusbendtsen)\
**Replies:** 1\
**Last updated:** [May 11, 2022, 10:44am UTC](https://discourse.datamethods.org/t/is-it-the-numerator-or-denominator-which-explains-variations-of-a-ratio/5600 "2022-05-11T10:44:32Z")

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We are studying a collection of reports which account for the number of diagnosed cases of a disease at different hospitals pre- and during the Covid-19 pandemic. Cases are counted over comparable time intervals (for ins…

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## [Overconfident forecasts in infectious disease epidemiology](https://discourse.datamethods.org/t/overconfident-forecasts-in-infectious-disease-epidemiology/5628)

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**Author:** [@ChristopherTong](https://discourse.datamethods.org/u/ChristopherTong)\
**Replies:** 5\
**Last updated:** [May 11, 2022, 7:30am UTC](https://discourse.datamethods.org/t/overconfident-forecasts-in-infectious-disease-epidemiology/5628 "2022-05-11T07:30:32Z")

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In 1984, Picard and Cook published a classic paper on cross-validation of regression models (JASA 79: 575-583) in which they defined the Optimism Principle: “a model chosen via some selection process provides a much mo…

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## [Collider bias question](https://discourse.datamethods.org/t/collider-bias-question/5464)

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**Author:** [@Pavel\_Roshanov](https://discourse.datamethods.org/u/Pavel_Roshanov)\
**Replies:** 4\
**Last updated:** [April 21, 2022, 7:22pm UTC](https://discourse.datamethods.org/t/collider-bias-question/5464 "2022-04-21T19:22:16Z")

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I was hoping someone can help me work out potential for collider bias in the following scenario: Exposure (E) potentially causes one of the model covariates (A) used to adjust the exposure-outcome relationship. (I rec…

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## [Advice on study examining mortality rates and differences between exposed and general population](https://discourse.datamethods.org/t/advice-on-study-examining-mortality-rates-and-differences-between-exposed-and-general-population/2983)

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**Author:** [@beespeev](https://discourse.datamethods.org/u/beespeev)\
**Replies:** 5\
**Last updated:** [April 11, 2022, 6:36am UTC](https://discourse.datamethods.org/t/advice-on-study-examining-mortality-rates-and-differences-between-exposed-and-general-population/2983 "2022-04-11T06:36:43Z")

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I have been asked to provide some advice on a study examining differences in mortality rates between a cohort of individuals followed from the 1960s to now, with deaths recorded in every year. I want to get a sense of wh…

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## [Adjusting for confounders in economic conditions](https://discourse.datamethods.org/t/adjusting-for-confounders-in-economic-conditions/2911)

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**Author:** [@Lghimire](https://discourse.datamethods.org/u/Lghimire)\
**Replies:** 2\
**Last updated:** [January 21, 2020, 10:52pm UTC](https://discourse.datamethods.org/t/adjusting-for-confounders-in-economic-conditions/2911 "2020-01-21T22:52:00Z")

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This is my first question on this forum. I am studying a condition that is common in early childhood. I am analyzing nationwide data. My hypothesis is that the condition is more common in children living in poorer neighb…