st: RE: Average age at first occurrence analysis

["Kieran McCaul" <kamccaul@meddent.uwa.edu.au>]

You can fit Weibull models in Stata with -streg-.

I don't know of any specific material available explaining how to fit age-at-onset models; presumably age is used as the survival time.

You could have a look at the UCLA website: http://www.ats.ucla.edu/stat/stata/topics/survival.htm
It at least has some tutorials on fitting Weibull models for survival analysis.




______________________________________________
Kieran McCaul MPH PhD
WA Centre for Health & Ageing (M573)
University of Western Australia
Level 6, Ainslie House
48 Murray St
Perth 6000
Phone: (08) 9224-2140
Fax: (08) 9224 8009
email: kamccaul@meddent.uwa.edu.au
http://myprofile.cos.com/mccaul 
http://www.researcherid.com/rid/B-8751-2008
______________________________________________
The fact that no one understands you doesn't make you an artist.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Andrew John Brunskill
Sent: Thursday, 12 February 2009 9:47 AM
To: statalist@hsphsun2.harvard.edu
Cc: jaberwok@u.washington.edu
Subject: st: Average age at first occurrence analysis

Please would any kind people suggest some stata commands that would allow me to calculate estimated average times , using Weibull type models, with particular emphasis on their use in case only designs. The only reference in the stata list I can find is on the shared frailty model but most of the sources I can find are on the Cox (proportional hazards) model.  There was a very valuable paper by Boshuizen HC and Greenland S Int J Epidemiology 1997 26 4 867 Average age at first occurrence as an alternative occurrence parameter which encouraged the development of suitable packaged software allowing the fitting of these models  and an excellent but scary paper by Wilk JB and Lash TL Emerging Themes in Epidemiology 2007 4:1 Risk factors studies of age-at-onset..:a cautionary tale  which shows the methodological and interpretative problems.  Prof Greenland has been kind enough 
to clarify for me what I need to understand.  What I would love to get as a reasonably numerate medical epidemiologist ( but not someone who models bus waiting times in greek numerals in my head (alas!) )is a good book or source (lecture notes??)  with some worked commands in hopefully stata.  My work is on data on kidney failure and transplant so it might even be helpful  to some other people sometime!   Thanks very much for any replies. Andrew Brunskill andrew@anzdata.org.au

Andrew J Brunskill,
University of Washington  jaberwok@u.washington.edu
Fellow in Epidemiology ANZDATA andrew@anzdata.org.au




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