Hi,
Thank you Joe for noticing the recent publication of a quantitative
model relating age and sex to weight across the human life span (Sumpter
& Holford 2011).
The WHO growth charts are just that -- charts i.e. a picture with some
lines on it. The model that Anita and I have proposed is quantitative
and includes both fixed (post-menstrual age, sex) and random effects to
describe the increase in weight in a sample of similar size to that used
for the WHO charts. Although the model is quite empirical we noticed
that sex is associated with weight differences only in the very young
(<1 y) and after about 12 y of age. Children in between these ages have
similar weight for age irrespective of sex.
We did not find any quantitative models published before but if
Nyashadzaishe did find some please let us know. We would be happy to
send the NM-TRAN code for our model and its parameters if anyone wants
to use it.
The population we used is perhaps more appropriate for simulations of
weight in clinical trials because we used subjects who had been
participants in clinical trials (mainly PK studies). The WHO population
was selected to represent the ideal pattern of growth with what was
thought to be optimal nutrition.
If anyone would like to contribute data (age, weight, sex are all that
is required for each subject) then we would be happy to extend our
analysis. Our data tended to be concentrated in the under 1 year of age
group so more observations in older children and adults would be very
useful.
Best wishes,
Nick
Sumpter AL, Holford NHG. Predicting weight using postmenstrual age --
neonates to adults. Pediatric Anesthesia. 2011;21(3):309-15.
On 18/02/2011 3:09 a.m., Standing Joseph (GREAT ORMOND STREET HOSPITAL
FOR CHILDREN NHS TRUST) wrote:
Nyashadzaishe,
UK and I believe WHO growth charts are derived using LMS method which
you can do in R - look for papers by TJ Cole. I also suspect you
might get a response from a certain NHG Holford telling you to look at
his NONMEM method: Paediatr Anaesth. 2011 Mar;21(3):309-15 - I have
only skimmed this paper but I think the introduction gives a review of
possible methods.
BW,
Joe
------------------------------------------------------------------------
*From:* [email protected] [[email protected]] On
Behalf Of nyashadzaishe mafirakureva [[email protected]]
*Sent:* 17 February 2011 13:24
*To:* [email protected]
*Subject:* [NMusers] Growth Curve Modelling
I am trying to model growth in children (1-20 years) with a particular
disease condition in NONMEM, R or any other software. There seem to be
a lack of concensus in literature on the functions (models) one can
use. I am therefore looking for some pointers from anyone who could
have worked on something similar before.
Thank you
--
Nyashadzaishe Mafirakureva
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--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology& Clinical Pharmacology
University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53
email: [email protected]
http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford
