EBM and Clinical Support Librarians@UCHC

A blog for medical students, faculty and librarians about their use of evidence based medicine, clinical literature, Web 2.0, sources and search strategies

Tag Archives: Global Epidemiology

Teaching & Learning in Medicine, Research Methodology, Biostatistics: Show Me the Evidence (Part 4): Causality, Airplanes and GIDEON

As accident re-enactments go, this one is pretty Riveting

Links courtesy of NJ.com and Exosphere3D – All rights reserved – Copyright 2011


The focus and calm of U.S. Airways Captain Chesley Sullenberger can be appreciated by listening to the audio portion of this re-enactment, as he made critical analyses – over a period of only a few minutes – on how (and where) to land a disabled aircraft sinking earthward over a densely populated area. His decisions saved 100% of the lives on board that day.

Hang out with a bunch of epidemiologists long enough and eventually the conversation while turn to Causality. They will tell you that there are some big differences in semantics between linking causation, etiology and “proof” that X exposure caused Z disease or health condition. When I looked up the terms “causation” and “causality” (on Google) there were major sidetracks, such as WBA (Why-Because-Analysis) as in, Why did the airplane crash? Why did the reactor experience a meltdown?

Why? From the viewpoint of a physician, an engineer or an epidemiologist… because of X-Y-Z.  

X-Y-Z could be bird strikes, human error, engine failure, weather conditions, crazed people bearing guns, lack of fuel or a thousand other accidents waiting to happen. Often the causes can be identified. Sometimes one can only attribute unanticipated events to gauzy, fuzzy concepts such as “it was a one in a million chance” or “this was God’s will”,  “causes unknown” or just plain Karma. The harder (non-fuzzy) data can be applied towards improvements in systems design, development of new vaccines, engineering safety… all targeted towards avoidance of future accidents (or disease outbreaks).


Epidemiologists save lives.  Sometimes this association accumulates slowly… as in proving associations between Exposure X and development of Disease Y decades later.  In other cases, evidence mounts up as an emergency, such as the identification of a novel virus identified as SARS in 2002.  But linking health effects of exposures over a human life-span is so much more elusive than showing evidence that birds got sucked into a jet engine at 2,500 feet (as above).

Turning to the PubMed database, a screenshot below from Medical Subject Headings List (MeSH) reveals how the term “causation” is mapped in the online thesaurus of medical indexing terms:

Image Source: NLM (http://www.ncbi.nlm.nih.gov/mesh) – All rights reserved – copyright 2011

One way to search a large database such as PubMed is to simply type in some words – for an example, Liver Cancer AND Epidemiology.  This pulls up over 18,000 retrievals…  too many (!), but by then selecting and applying standard Limit Fields such as Language, Journal Subset, Age Group, Gender and others, the retrievals can be filtered down to a more-manageable number.

A more precise way to search a large database like PubMed is to use the Medical Subject Headings list. In the example below, the term Liver Cancer was typed into the MeSH search page, which maps automatically to the preferred MeSH term — Liver Neoplasms. While this search still retrieves thousands of citation, they can be limited by selecting and applying any MeSH Subheading (or clinical qualifiers) that are appropriate to the search. These subheadings include clinical concepts such as Virology, Immunology, Genetics, Epidemiology, Transmission and 80 others.  Following is a screenshot of that type of search:

Image Source: NLM (http://www.ncbi.nlm.nih.gov/mesh) – All rights reserved – copyright 2011

Remember that a librarian’s idea of “causality” could be defined, in part, by the number or types of clinical subqualifiers selected (immunology, virology, epidemiology and those types of “background” concepts) to be combined with the formal MeSH term.

There are many ways to search. It helps a novice medical searcher sometimes to tell them just that: There is no one right way to search. Sounds enigmatic and it is.

Here is an example which I found recently in the medical literature, a 2010 article which discusses application of Bradford Hill criteria (listed here):

  • strength of association
  • consistency
  • specificity
  • temporality
  • biological gradient (dose-response)
  • biological plausibility
  • biological coherence
  • experimental evidence and
  • analogy

 Image: http://www.ncbi.nlm.nih.gov/pubmed/20644061 – All rights reserved – Copyright 2011


Those searching for practical answers about causality, transmissible agents, disease etiology, global prevalence or current treatments might want to search GIDEON (Global Infectious Disease Epidemiology Online Network), an interesting “niche” information source targeting the research requirements of epidemiologists, clinical & translational researchers, MPH students, toxicologists or anyone interested in tracking or diagnosing infectious diseases on a country- or world-wide scale (subscription required). Updated weekly, the database is produced by Gideon Informatics and hosted on the EBSCO platform.

A search for causality or epidemiology done in the resources indexed by GIDEON is quite unlike a search done in PubMed about the etiology of Liver Cancer. The producers collect, review and index factual data collected from around the globe; their data encompasses a wide and diverse group of human cultures, agricultural, societal, economic or environmental practices.

Below is a screenshot of one example of the type of data that can be searched on GIDEON: bacterium (causative agent), typhoid (identifiable infectious agent) and United States (location, recorded incidence over time):

.Finally, a screenshot of What’s New at GIDEON (May 11 2011):

Image Source: GIDEON – All rights reserved – copyright 2011


News, Public Health, Global Health: A Potential Pandemic of Influenza

Public health concerns dominate the news headlines this week, as evidence continues to unfold of a global outbreak of a novel strain of swine influenza A/H1N1.

Thanks to an active international group of Medical Bloggers and Librarians connected through social networking sites such as FriendFeed or Twitter, as I arrive at work on Monday morning, this connectedness becomes a great advantage for those of us in the United States, as our European colleagues have already scanned and posted many news or website links on items of vital concern, as emerging news continues to pour in from many places around the world.

Following are a brief set of links to global health information, disease-tracking and interactive-maps for the spread of Swine Influenza A/H1N1 (reported as of Monday, Apr 27 2009):



Image credit:  http://www.tweetdeck.com – All rights reserved – Copyright 2009


  • The International Society for Infectious Diseases (ISID) produces ProMed-Mail, described as the global electronic reporting system for outbreaks of  emerging infectious diseases & toxins, open to all sources“. Subscription to ProMed-Mail is available to anyone, free of charge; updates can be set up for daily or weekly email alerts.
  • UCHC Library subscribes to GIDEON (Global Infectious Diseases and Epidemiology Online Network), which is a specialized database for epidemiologists used for “… diagnosis and reference in the fields of tropical and infectious diseases, epidemiology, microbiology and antimicrobial chemotherapy.  GIDEON currently tracks 337 diseases, 224 countries, 1,147 microbial taxa and 306 antibacterial (-fungal, -parasitic, -viral) agents and vaccines, including over 10,000 notes outlining the status of specific infections within each country and over 20,000 images, graphs, interactive maps and references“.  GIDEON is updated daily.

United States

Tracking the Outbreaks

  • Google provides a free service called News Alert, which you can create yourself using any key-words to search on.


I’d like to acknowledge the cooperative work of many European scientists and medical librarians – and in particular, bloggers Laikas, Berci and DigiCMB – who are always 6-8 hours ahead of me, both literally speaking in the real world and in many Web 2.0 innovations, who have posted scientific links and news about swine flu and steered  me to several links for this post today.   Thank you to these talented, and generous, colleagues.

Medical News, Public Health: Research on Shift Work, Circadian Disruption and Human Cancer Risk

In the news this past week have been research updates on the deleterious effects of night shift work upon human cancer risk. The International Agency for Research on Cancer (IARC), a part of the World Health Organization, conducts, coordinates, collects and disseminates information relating to carcinogenic substances, clinical causes of cancer and strategies for the control of this disease in humans throughout the world. It is the agency which publishes IARC Monographs on the Evaluation of Carcinogenic Risks to Humans.

A subsection of this series, “Overall Evaluations of Carcinogenicity to Humans: Group 2-A: Probably Carcinogenic to Humans“, was updated on Nov 29 2007. Read a press release from IARC announcing this update, which now lists Night-Shift Work as an environmental exposure assumed to be a “probable human carcinogen”. On the IARC website is also CancerMONDIAL which collects and publishes a periodical entitled “CI 5: Cancer Incidence on Five Continents”, free online at http://www-dep.iarc.fr/

The December 2007 issue of the journal Lancet Oncology (Volume 8, Issue 12) will feature an article detailing the latest research on circadian disruption, entitled “Carcinogenicity of Shift-Work, Painting and Fire-Fighting“.

London writer Maria Cheng wrote a news article entitled “Graveyard Shift Work Linked to Cancer” available on Wired.com (Nov 29 2007). However, the recent 2007 news reports are far from the first time the subject of circadian rhythm disruption, melatonin production, night-shift work and cancer risks have been reported by epidemiologists and cancer researchers.

As another brief example, following is a link to a 2001 news item from the Seattle Post-Intelligencer reporting on two surveys of American nurses published in 2001. The researchers found that the more nights, and more years, nurses worked during graveyard shifts, the higher their likelihood of developing breast cancer. In one group studied, the risk was estimated to be elevated by 60%. Read the news article here.

Dr. Richard G. Stevens, professor of community medicine at UConn Health Center, has been studying the effects of electronic light sources on human health for more than twenty years. He wrote in 1987 an article entitled “Electric Power Use and Breast Cancer: A Hypothesis“, published in American Journal of Epidemiology, Vol. 125, Issue 4 (1987). Here is a screenshot of a few of his recent citations, found on PubMed:


Dr. Stevens was one of three epidemiologists who were recently interviewed on the National Public Radio series, Where We Live which was broadcast on WNPR (Connecticut National Public Radio station) on Nov 30 2007.

Other scientists featured on this program were IARC epidemiologist Dr. Vincent Cogliano (a co-author of the Lancet Oncology article cited above) and Dr. Mark Rea, Director of the Lighting Research Center at Rensselaer Polytechnic Institute. Their interviews are available as a podcast (screenshot follows):


Image and Podcast courtesy of National Public Radio and WNPR – Copyright 2007 – All rights reserved.