|pygmy growth 1-5yr||Michael H.N. Golden||01.07.97|
|Ok and pygmies||Michael H.N. Golden||05.07.97|
Date: Wed, 25 Jun 1997 17:18:38 +0000
An enquiry from SCF's programme in eastern Zaire:
Can international anthropometric standards be used to assess the nutritional status of under-five year old pygmy children? Some say that their growth upto five years is similar to that of normal children and, therefore, that standards can be used; others say not.
Does anybody out there know?
Lola Nathanail, Livelihoods (Food and Nutrition) Adivser
Policy Unit, SCF(UK)
Date: Thu, 26 Jun 1997 12:39:15 +0100
Regarding Lola's query on the growth of Pygmies, I just had a word with Mercedes de Onis who said that the few studies carried out show that their growth (under 5 years) seem to be the same as other children in that age group. There is a difference in growth only after about the age of about 12 years.
Subject: pygmy growth 1-5yr
Date: Tue, 1 Jul 1997 15:43:19 +0100 (BST)
From: "Michael H.N. Golden" <m.goldenatabdn.ac.uk>
Lola asks about the growth of Pygmies aged 1-5 and if international standards can be used for the programs now being mounted in Congo (Zaire).
Merimee TJ et al (Insulin-Like growh factors in Pygmies. NEJM 316,906-911, 1987) measured about 600 from the Ituri Forrest (group not stated) and did some endocrinological measurements. The growth was less than the NCHS standards but was similar to local Bantu controls. (3year 88.8 vs 90.0 cms; 5year 99.1 vs 102.0 cm; 10yr 120 vs 123.1; 16 yr 140 vs 155.3). It is quite clear from the longitudinal data that pygmies have no pubertal growth spurt and stop growing at about 10-12 years of age.
However, Mann (the riddle of pygmie stature. NEJM 317;709;1987) published cross-sectional data from the 1960's that showed range of height to be below the 20th centile and the average below the 3rd centile from 2 years and that they stopped growth at 10 years.
The difference between the two studies was ascribed to socio-economic/nutritional factors rather than inherent differences by Merimee. Particularly the very high parasite burdens they carry (Am J Trop Med Hyg 12;383-7;1963).
From these data alone International standards would seem to be reasonable - however, it is not at all clear that the differences are due to socioeconomic/nutritional differences. In this respect the different groups of pygmies may give different results. We do have growth data from birth to 5 years measured longitudinally in Efe pygmies; these data show that pygmies are indeed smaller from birth. Here is the abstract of this paper: Bailey RC. The comparative growth of Efe pygmies and African farmers from birth to age 5 years. Annals of Human Biology. 18:113-20, 1991.
Recent studies of African pygmies have concluded that the pattern of pygmy growth is similar to that of other Africans up to the time of puberty and that the short stature of adult pygmies is due primarily, if not solely, to the absence of accelerated adolescent growth. These conclusions are thought to be consistent with biochemical studies showing pygmies to have low levels of insulin-like growth factor 1 (IGF-1). All previous pygmy-growth studies have been of subjects of estimated, not known age. This paper reports the results of a mixed longitudinal growth study of Efe pygmy children of known age from birth to age 5 years. The mean adult stature of Efe pygmies is the shortest of any human population known, including other pygmy populations of central Africa. At birth, Efe were significantly smaller than neighbouring Lese Sudanic-speaking farmers and other rural Africans. During the first 5 years of life, Efe not only remained shorter than Lese controls at all ages, but the difference in stature between them increased. Unlike the Lese, Efe children showed a trend of increasingly negative z scores compared with the American reference population, from -2.71 (SD = 0.93) at 6 months to -4.16 (SD = 0.46) at age 5 years. These results indicate that suppression of pygmy growth does not occur solely at puberty, but from birth onward. Furthermore, they suggest that conclusions concerning the lack of an adolescent pygmy growth spurt have been premature and must await studies of older pygmy sub-adults of known age.
That these data are correct is supported by measures of size versus development. Tronick EZ and Winn SA (The neurobehavioral organization of Efe (pygmy) infants. J Development Behavior Pediatr 13:421-4, 1992) compared development in 6 Efe-Mbuti (pygmy) infants (This subgroup are the smallest well-grown, full-term infants in the world, with, length and weight below the 10th percentile but wt-for-ht above the median). Their development was compared with three groups of full-term infants: two normal height, well-grown infants (Africa and USA) and a group of symmetrically growth-retarded infants. The behavioral development of the Efe infants was similar to that of the well-grown infants and superior to the growth-retarded infants. The shows that the small pygmy infants are not at all "retarded" as one would expect if their small stature was due to socio-economic/nutritional deprivation.
Thus, at present it would seem that international standards of height-for-age are not applicable to all groups of pygmies. However, it may well be that weight-for-height standards could be used - I have not seen data to support or refute this.
Of potential importance is the observation that pygmies (adults) have a decreased insulin output in response to glucose/arginine and develop prolonged hypoglycaemia when insulin is given. Children have not been studied to my knowlege. However, hypoglycaemia may be a particularly severe problem in malnourished pygmies. It would be useful to document whether or not this is the case, and whether the clinical expression of malnutrition is the same as in other genetically distinct groups.
Prof. Michael H.N.Golden
From: "Stanley Ulijaszek (NDFS)" <ULIJASZEKathealth.curtin.edu.au> Organization: Public Health, Curtin University of
Date: Thu, 3 Jul 1997 09:56:12 WST-8
Comments on a similarly small population in Papua New Guinea. The Mountain Ok are a short stature population, whose weight and height for age showed (at time of survey, when a significant modernization event took place, the building of a gold and copper mine in their remote habitat) steady deviation from British references from birth, including a rather difficult to discern pubertal growth spurt (Lourie et al, Annals of Human Biology, 1986, 13, 517-536). The authors conclude that this is an adaptive response to chronic nutritional deprivation. Work by Schwarz et al (cited in Bogin's 'Patterns of Human Growth', 1988, Cambridge University Press) suggests that serum levels of GH, IGF-1, IGF-2 are in the normal range, and again, that the low stature is due to nutritional deprivation. A comparison of the rapidly modernizing Mountain Ok measured in 1975 (before the mining, when they were traditional hunter-horticulturalists), 1982/3 (when the mining operation started) and 1987 (when the majority of these people were involved in the cash economy) shows that they are getting heavier, and to some extent taller (in Ulijaszek, 1995: Development, modernisation and Health Intervention, In: Health Intervention in Less Developed Countries, ed S.J. Ulijaszek, pp 82-136, Oxford University Press), this being attributed to nutritional improvement. The fact that a population shows steady decline/deviation from growth references or another population does not support the argument that the distinct smallness of a population is not nutritional. ie. despite Bailey, I support the view that international growth references can be used for Pygmy populations, between the age 1-5 years.
Professor Stanley J. Ulijaszek
Department of Nutrition, Curtin University School of Public Health
Perth WA6001, Australia
Sat, 5 Jul 1997 17:17:33 +0100 (BST)
Subject: Ok and pygmies
From: "Michael H.N. Golden" <m.goldenatabdn.ac.uk>
The same arguements about nature and nurture surrounded other populations until Renaldo Martorel published the data from Elite ethnic groups. Perhaps Renaldo would like to comment about the Pigmies? Are there any data from "elite pygmies" I doubt it.
Although I agree that nearly always environmental hardship is the main cause of short stature, I would not discount a genetic component in the pygmies. This is because of the placental mitochondrial DNA sequencing data. there are about 2 base substitutions per 5 generations (100yrs) and no repair machinery - so that from the sequences a latest-common-ancestor for two peoples can be determined. Surveys show that the genetic diversity within Africa (at least 7 different pedigrees) is greater than in the rest of the world put together. I (Caucasoid) am closer genetically to an Australian Aboriginal than a Dinka is to a Hotentot. Showing that the rest of the world (including the Ok people) has more or less the same genetic growth does not necessarily hold for African groups. Clearly the rift-valley people and the west-coast population that gave rise to the slaves have growth genetics like the rest of the world - but pygmies, who do NOT have normal IGF-I or in-vitro ICF-I responses or pubertal growth spurt, could well have a genetic growth curve difference. They almost certainly ALSO have nutritional deprivation however. The topic must remain sub judice until we have the data.
From a pragmatic point of view I also would use weight-for-height and MUAC international standards for pygmies - until we know better. To say that this population needs nutritional help because of their height-for-age deficit is not going to do any harm and is likely to do a great deal of good, so despite the uncertainty from an academic point of view, from a practical point of view I would advise those organising the programs to use the international standards "pro temporare". The problem might be to persuade donors that the survey data indicate a real need - now we have a very authoratative opinion from Stan - that can be used to back arguments to Donors for action, and a concensus.
Prof. Michael H.N.Golden