Mary,

I responded to your survey as soon as I read it because it took me only a
few minutes.  I did it, however, even though surveys of this kind are
usually not reliable.  It is not that the questions you asked were
deficient in any way, and I believe you would be objective in evaluating
the answers.

It is because retrospective studies are usually not a reliable way to
establish correlations.  I say usually because if everyone on the list
answered and gave the same answer, you would indeed have uncovered
something of value.  But, results seldom turn out that way.  Usually the
correlations one might observe in retrospective studies have no validity
and are useful only as a suggestion of one thing to look for in a more
reliable subsequent study.

This point was made an article by William Feller in the throwaway
periodical 'Scientific Research' many years ago.  I remember it well
because it impressed me so much.  Feller is the author of the book for a
course on probability that I took.  He was the first to present the subject
in the now accepted way.  The book went through a number of printings.  He
is well respected.

His article in 'Scientific Research' was short and to the point.  He
probably chose that magazine because he wanted as many people as possible
to get the message, which no doubt is widely known by probability theorists
and mathematical statisticians, but seems frequently to be ignored by
epidemiologists.

Feller said that if you consider 100 uncorrelated random variables
generated by a computer and calculated the correlations between all pairs
of them, you would find at least one pair with a convincingly large
numerical correlation.  I do not recall the exact number, but I think it is
something like 25 per cent or more, maybe even 50 per cent.  Statisticians
would say that value of the numerical correlation is  'statistically
significant.'  There are also a surprisingly large number  of pairs for
which the calculated correlations are large enough that someone who didn't
know the source of the data might say that there is convincing evidence of
a correlation.   Again I do not recall the exact numbers, but I think they
are in the 5 percent to 10 percent range.  All this for random numbers with
absolutely no real (i.e. causal) correlation.

I am not an expert in statistics, and so I do not have definitive
information to give you about this.  I certainly am not skilled in
designing a careful study.  But I think Feller's point leads one to be
cautious about the interpretation of retrospective studies.

Baldwin, 63/4
8x25/100 carbi/levo-dopa,  5 mg Eldepryl per day
[log in to unmask]


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From:  Mary Sheehan
Sent:  Thursday, October 23, 1997 11:06 PM
To:  Multiple recipients of list PARKINSN
Subject:  Response to PD Survey

My PD started 11 years ago with a frozen shoulder.  Bradykinesia and
micrographia followed, but the doctors attributed my symptoms to the
effects
of the frozen shoulder.  It wasn't until 21 months ago that I was diagnosed
with PD. After 11 years with PD, I am still in stage 1. I take only 5mg of
Eldepryl daily and have recently started to take Mirapex.

I am telling you this so you will understand my motivation for doing the
survey.  I have been amazed at the different rates at which PD progresses,
 the different symptoms in each person and the different ways that each
person is medicated.  I came up with a premise that the progression and
symptoms of PD must relate to either personal lifestyle or to how PD
presents
in an individual .... or possibly to a combination of both.  I had hoped to
use the resources of this list to find a pattern that made the progression
of
PD more predictable.  I have done some successful research in the past,
although not in the medical field, and felt there were clues out there
waiting to be uncovered.

Unfortunately, with only 18 responses, it was impossible to draw any
conclusions.  I had hoped for 100 responses, or more, out of the 1500
people
on the list.  What really upset me was the responses i received as to why
people didn't respond.
" I'm too busy to reply".  The whole survey couldn't have taken more than 5
minutes to fill out. Most questions required only one-word answers.
"I'm tired of all the surveys on this list."  In the year and a half I've
been on this list I recall only two persons doing a survey.  I answer
surveys
in the small hope that maybe something will come out of it that will help.
"The PD organizations can"t get together".  So let them do their research
separately.  I have great respect for the researchers at the Parkinson's
Institute and for my neuro who also does research and whom I thought would
be
interested in what we had to say.

I'm sorry to be so wordy.  I put in several hours of work on the survey and
was annoyed to find my efforts denigrated.  I'm probably only having a bad
day, but I'm disappointed because I honestly thought we might put our heads
together and discover something.  I will shut up now and in the future will
avoid initiating surveys .  Thanks for letting me vent.

Mary