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J R Soc Med. 1987 September; 80(9): 544–546.
PMCID: PMC1290995

National Study of Health and Growth: effect of change in design with reference to efficiency of mixed longitudinal studies for measuring trends.


The National Study of Health and Growth (NSHG) is a surveillance system which monitors the growth of primary school children in England and Scotland, set up in 1972 following changes in the school milk and welfare system. However, the study contained few children from inner city areas or ethnic minorities. In 1982 its design was changed from one in which the same areas were surveyed every year, to two separate systems with areas surveyed every two years, one set of areas corresponding to those in the original study, and the other set consisting of inner city and ethnic minority areas. The precision of the estimates of trends in height and weight for each system was smaller than that of the original system, but by less than 50%, so that an overall gain in information was achieved. Studies of mixed longitudinal design are shown also to be generally, but not always, less efficient for estimating trends than independent cross-sectional surveys obtaining the same number of measurements.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Altman DG, Cook J. A nutritional surveillance study. Proc R Soc Med. 1973 Jul;66(7):646–647. [PMC free article] [PubMed]
  • Irwig LM. Surveillance in developed countries with particular reference to child growth. Int J Epidemiol. 1976 Mar;5(1):57–61. [PubMed]
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  • Cook J, Irwig LM, Chinn S, Altman DG, Florey CD. The influence of availability of free school milk on the height of children in England and Scotland. J Epidemiol Community Health. 1979 Sep;33(3):171–176. [PMC free article] [PubMed]
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  • van't Hof MA, Roede MJ, Kowalski CJ. A mixed longitudinal data analysis model. Hum Biol. 1977 May;49(2):165–179. [PubMed]
  • TANNER JM. Some notes on the reporting of growth data. Hum Biol. 1951 May;23(2):93–159. [PubMed]

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