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EVIDENCE-BASED-HEALTH  June 2011

EVIDENCE-BASED-HEALTH June 2011

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Subject:

Re: Help with appraisal of a cohort study please

From:

Brian Alper MD <[log in to unmask]>

Reply-To:

Brian Alper MD <[log in to unmask]>

Date:

Wed, 22 Jun 2011 13:00:21 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (78 lines)

Before trying to use this study to support or refute resource allocation decisions I'd caution about considering the difference between clinical outcomes (outcome of current respiratory symptoms, or symptomatic COPD) and surrogate outcomes (spirometric measurements consistent with COPD but not obtained in the clinical context of patient suffering)

Associations with surrogate outcomes only should be considered part of the story in development, not the "answer" to guide such decisions.  Perhaps smoking has a greater impact on clinical ailments and resource use for COPD (assuming you have a forced choice and have to quantify relative impact) but the clinical impact is not necessarily through the spirometric measurements.


Brian S. Alper, MD, MSPH
Editor-in-Chief, DynaMed
Medical Director, EBSCO Publishing
[log in to unmask] 
www.ebscohost.com/dynamed 
 

 DynaMed Weekly Update - Timely information on articles most likely to change clinical practice in a FREE weekly e-newsletter from the DynaMed Editors. Earn FREE CME for reading the update.


-----Original Message-----
From: Evidence based health (EBH) [mailto:[log in to unmask]] On Behalf Of Paul Elias
Sent: Wednesday, June 22, 2011 12:55 PM
To: [log in to unmask]
Subject: Re: Help with appraisal of a cohort study please

 was there a reason why the cohort was not followed for the full period and then 
the attempt at association made in 2002, looking back at the early life factors? 
I do not understand why they would pool the measurements... can you explain a 
bit more from the methods....?? 
 
 
 
 
 
Best,

Paul E. Alexander
 



----- Original Message ----
From: Anne Gray <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, June 22, 2011 12:36:14 PM
Subject: Help with appraisal of a cohort study please

Hi all
Can I ask for your collective thoughts on a paper published in Thorax please? 

The study aims to use a cohort study to identify associations between childhood 
factors and reduced lung function and therefore risk of COPD. Interviews 
identidied a range of early life factors in a multisite cohort (n=13,359)of 
participants age 20-45 in 1991-1993, then repeated the measurements 9 years 
later in 7738 of  the participants.
The two sets of measurements have been added together, giving n= 16,832 to make 
associations between childhood factors an dreduced lung function.

I am concerned that they are counting some people twice to make the association. 
Is this appropriate?

Interestingly there is no signficant association between these supposed 
childhood factors and decline in lung function over time (ie in those measured 
twice.)

THis does have implications - if childhood factors are more important that 
current smoking rates we may have to rethink stop smoking services.
I have tried to contact the author but no response so far.

I am happy to be told that this is appropriate and my understanding is wrong. I 
would just like to be able to explain the study to my Stop Smoking lead.

The article is:

THorax 2010 v65 p14-20
Early life origins of COPD
Svanes et al
http://thorax.bmj.com/content/65/1/14.full 
thanks

Anne Gray
NHS Milton Keynes

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