[ RadSafe ] Re: Shipyard worker study

Thu Feb 8 20:36:10 CST 2007

Keith -

Here are a few notes that I hope will be helpful -

1. The NSWS did _not_ compare workers vs. non-workers.
 The reason is that there is a well-known phenomenon
in epidemiology called the "healthy worker effect." 
Basically, a sample of folks who go to work every day
and live "normal lives" is a somewhat more selective
sample than a general sample of the 18-65 y,o. total
population would be....because the general population
includes a number of individuals with significant
health or behavioral problems.  These problems that
may preclude work include physical disabilities,
mental disabilities, prisoners, addiction, and some
others.  Just as a simple example - prisoners have
higher HIV and hepatitis B  rates than the general or
working population.  A sample of workers (that
excludes prisoners) is going to be "healthier" with
respect to HIV, hepatitis B and tuberculosis because
prisoners and a large proportion of drug users were
excluded.

http://www.ajph.org/cgi/content/full/94/7/1218

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16186458&query_hl=11&itool=pubmed_docsum

2.  That being said, there *are* quite a few studies
that compare workers to non-workers.  One of the best
is the study of British radiologists in which
radiologists were compared with *both* other
physicians and also with a couple of groups of the
British population (by social class).  This was a
carefully-conducted study by the late Sir Richard
Doll's group that showed reduced mortality among
radiologists.

http://bjr.birjournals.org/cgi/content/full/74/882/507?ijkey=c9f466a7d8938a1ce9c05f1959a0e3fe20f557a9

See the citations for discussion.  This articles is
rather well-cited.

3.  Some studies have compared incidence of an illness
- e.g. breast cancer - across a variety of
occupations.  These are basically worker-to-worker
comparisons involving a wide variety of occupations.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7796201&query_hl=14&itool=pubmed_docsum

In this case, "high risk" occupations included
housewives, registered nurses, clinical laboratory
technicians, schoolteachers, social workers,
secretaries and typists, and meat wrappers and
cutters.

4.  For many more citations involving both
worker-worker comparisons and worker-general
population comparisons, see

http://www.radscihealth.org:9000/rsh/dd3/_database.jsp

5.  Regarding the specific question in Keith's email:
there are quite a few studies that compare workers of
various industries to non-workers.  Very often, the
worker cohorts are significantly healthier than
non-worker groups. 

Comparison of nuclear workers with a general
population in California -
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16808626&query_hl=36&itool=pubmed_DocSum

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16081494&query_hl=36&itool=pubmed_DocSum

Cancer incidence in Australian nuclear workers -

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17053302&query_hl=36&itool=pubmed_docsum

http://www.jstage.jst.go.jp/article/joh/48/5/48_358/_article

6.  Other workers - discussion of HWE (healthy worker
effect):
"Obvious cases" of jobs that require physical fitness
- where employees are obviously screened for physical
fitness before entering an occupation - 

major league baseball -
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16700406&query_hl=26&itool=pubmed_DocSum

football -
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17214401&query_hl=32&itool=pubmed_docsum

=More "normal" occupations -

"Healthy worker effect" also present in oil refineries
-

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=9172090&query_hl=24&itool=pubmed_docsum

"Healthy worker effect" tends to decrease as years of
employment go by...'new hires' may be screened for
health/fitness whereas those with seniority stay on,
despite having possibly picked up health problems. 

Example: German firefighters:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17020604&query_hl=26&itool=pubmed_docsum

7. Other aspects of work -
Overtime can cause injury/illness problems -

http://oem.bmj.com/cgi/content/full/62/9/588

Early retirement isn't always good -

http://www.bmj.com/cgi/content/full/331/7523/995

8.  UNhealthy workers - workers LESS healthy than
general population:
Interestingly, some "unhealthy workers" are as close
as the meatcutters in your local supermarket:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7951779&query_hl=16&itool=pubmed_docsum

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=9554414&query_hl=48&itool=pubmed_docsum

9. Studies of "excess relative risk" basically factor
out cardiovascular health and outcomes related to
infectious disease and accidents when comparing
nuclear workers to general population:

The Cardis et al. study has been controversial - other
listmembers may wish to discuss - 

http://www.bmj.com/cgi/content/full/331/7508/77

Hope these citations are helpful for a general
background on the subject -

~Ruth Sponsler

--- Keith Welch <welch at jlab.org> wrote:

> Thanks John,
> 
> The things I am wondering about (anecdotal
> information I've heard over 
> the years) don't have anything to do with asbestos
> exposure, but I 
> suppose that could be an issue.  However, I would
> think since asbestos 
> illness is fairly well identifiable (from what I
> understand) that 
> adjustments could be made for that.  It's hard to
> imagine that the 
> existence of asbestos illness in shipyard employees
> makes them 
> (generally) significantly less healthy than the
> general population.  I 
> have obtained a copy of the study, and one day,
> maybe I'll get a chance 
> to actually go through it and try to learn
> something.  My questions also 
> had to do with review of the study by Cameron and
> Sponsler.  I don't 
> recall seeing in that an indication that the
> unexposed cohort was less 
> healthy than general population, but I haven't
> studied it closely or 
> recently.  Does the shipyard study (or any other
> study) provide a 
> mortality comparison of the unexposed cohort with
> "general population"?
> 
> 
> John Jacobus wrote:
> > Keith,
> > Issues concerning the Navy nuclear shipyard study
> come
> > up periocially.  Maybe yearly?  You may want to
> check
> > the RadSafe achives.
> >
> > The primary flaw with the study is that the
> cohort,
> > unexposed shipyard workers may not have been as
> > healthy as members of the general population. 
> This
> > may be due to asbestos exposures. 
> >
> > Of course, some still quote the "favorable"
> aspects
> > while ignoring the question as to whether or not
> it is
> > even a valid study.
> >
> > --- Keith Welch <welch at jlab.org> wrote:
> >
> >   
> >> Folks,
> >> I am not an epidemiologist and have no experience
> in
> >> that field.  But 
> >> recently, partly due to the posts here, I have
> been
> >> wondering about 
> >> this.  Maybe I just haven't thought it through
> well
> >> enough.  It seems on 
> >> its face that using cancer incidence rates would
> be
> >> preferable to 
> >> mortality, due in part to the issue of changes
> over
> >> time in cure rates, 
> >> but also because it would seem to help correct
> for
> >> the healthy worker 
> >> effect (incidence rate is not as affected by the
> >> availability of health 
> >> insurance or treatment as mortality rate) - and
> >> possibly the "rich 
> >> victim effect", which I have not heard many
> people
> >> talk about, but 
> >> assume must be confounding; the difference in
> cure
> >> rates in different 
> >> socio-economic classes.  I would suppose that
> could
> >> probably be dealt 
> >> with by careful cohort selection.  At any rate,
> I've
> >> heard that the 
> >> shipyard worker study was flawed due to the
> >> following: (1) screening for 
> >> nuclear workers at the shipyards disqualified
> people
> >> with family history 
> >> of cancer, and (2) removal of people from nuclear
> >> worker status (and 
> >> therefore, presumably from candidacy for the
> study?)
> >> in the event they 
> >> were diagnosed with cancer during employment. 
> Are
> >> either of these based 
> >> in fact?
> >>
> >>     
> >
> >
> > +++++++++++++++++++
> > "We must face the fact that the United States is
> neither omnipotent or omniscient --- that we are
> only 6 percent of the world's population; that we
> cannot impose our will upon the other 94 percent of
> mankind; that we cannot right every wrong or reverse
> each adversity; and therefore there cannot be an
> American solution to every world problem."
> > -- John F. Kennedy 
> >
> > -- John
> > John Jacobus, MS
> > Certified Health Physicist
> > e-mail:  crispy_bird at yahoo.com
> >
> >
> >  
> >
>
____________________________________________________________________________________
> > Any questions? Get answers on any topic at
> www.Answers.yahoo.com.  Try it now.
> >   
> 
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