Hi Mija - would this one be of any use (look at Fig 1)?https://www.researchgate.net/figure/Shift-in-the-distribution-of-BMI-among-Chinese-adults-aged-20-45-years-in-1989-and_fig1_231772312 

Hi Mija - would this one be of any use (look at Fig 1)?https://www.researchgate.net/figure/Shift-in-the-distribution-of-BMI-among-Chinese-adults-aged-20-45-years-in-1989-and_fig1_231772312 

Hi,

Attached are our findings on the pattern of stunting in Venezuela, with a bell-saped curve illustrating the shift to the left.

https://www.frontiersin.org/articles/10.3389/fsufs.2021.638042/full

Regards,

Susana

Dear Mija,

The issue of the distribution of anthropometric indices is discussed in some detail in the 1995 WHO document on anthropometry available at:

https://iris.who.int/bitstream/handle/10665/37003/WHO_TRS_854.pdf

See pages 22 and following.

A spectacular example is show also in this article:

R Yip  1 , K Scanlon The burden of malnutrition: a population perspective. J Nutr. 1994 Oct;124(10 Suppl):2043S-2046S.

doi: 10.1093/jn/124.suppl_10.2043S.

In 2002 Golden and Grellety published a document on population nutritional status which is no more available on the web. In this document, they claimed that WHZ had a shifted distribution with a SD close to 1 suggesting a uniform shift to the left for all individuals. This seems biologically unlikely (variation is common to all biological processes) and may be based on the use of NCHS references for calculating WHZ. More recent estimations of SD of anthropometric indices suggests that WHZ and HAZ are shifted to the left with an increase of SD. See:

Mei et al. Standard deviation of anthropometric Z-scores as a data quality assessment tool using the 2006 WHO growth standards: a cross country analysis. Bull World Health Organ. 2007 Jun;85(6):441-8.

doi: 10.2471/blt.06.034421.

Just to add to Andre's points I think it’s always helpful to remember that black swans do, actually, exist. I remember a curious bi-modal HAZ curve I got from a refugee camp study. Was really puzzled until I learnt more about the population; half of whom had been surviving in the bush for months and half hadn't.

Thanks Andy +++. Very good point.

Also, in extreme situations, we may have a WHZ SD close to 1 when chidlren with extreme wasting died as suggested in the 1995 WHO report. But these are uncommon situations.