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Peter Bundred a University of Liverpool, Liverpool L69 3GB, b Royal
Liverpool Children's NHS Trust, Liverpool L12 7AP, c West
Hertfordshire Health Authority, St Albans, Hertfordshire AL1
3ER
Correspondence to: P Bundred peterb{at}liv.ac.uk
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Abstract |
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Objective:
To determine trends in weight, height, and body mass index in children between 1989 and 1998.
The increased number of overweight and obese children has been
highlighted in a cohort study of British children examined at 24, 49, and 61 months of age.1 We describe similar findings in a
large population based study, in which data were obtained from
measurements routinely performed by health visitors as part of the 6 week and preschool assessment. We examined trends in weight, height,
and body mass index in a defined population between 1989 and 1998.
Health visitors in the Wirral Health Authority of the North West
region review children regularly, and routinely collected data are
stored on computer. These data include weight (in grams), height (in
centimetres), date of birth, and date of the examination. Data from the
6 week and preschool assessments for the years 1989 to 1998 were
transferred to spreadsheet and statistical software for analysis. For
the 6 week assessment we included only infants aged between 28 and 90 days. For the preschool assessment we included children between 2 years
11 months and 4 years of age.
The study population consisted of 35 662 infants and 28 768 children.
Records of 21 582 infants and children (25%) were removed because of
missing or inaccurate data: in 13 240 (15%) full data were not
recorded; in 930 (1%) the weight or height was more than 5 SD from the
mean and was therefore considered inaccurate; and in 7412 (9%) the age
recorded did not match the age calculated from the date of examination
and the date of birth. As the date of birth was available for all
infants, it was possible to calculate the number of infants studied in
relation to the live birth rate for the area. The year 1998 was
excluded as some infants born late in this year will have been measured
in 1999. For the years 1989 to 1997 there were 37 292 live births in
the Wirral Health Authority area; of these we included 32 655 (88%)
in our study.
We calculated the body mass index for preschool children using the
formula (weight (kg)/height (m)2). This was not done for
infants aged 1 to 3 months as it is difficult to interpret body mass
index at this age. The height, weight, and body mass index were
standardised for age and sex with the British growth reference
charts
2 3
and the conversion programme obtained from the
Child Growth Foundation.4 The resulting standard deviation
(SD) scores were used in all calculations. An SD score of 0 represents
the 50th centile, 1.04 represents the 85th centile, and 1.64 the 95th
centile. An SD score >1.04 for body mass index (>85th
centile)
1 5
was defined as overweight and >1.64
(>95th centile) as obese.
Statistical analysis
Preschool children
Design:
Retrospective series of cross sectional
studies of routinely collected data.
Setting:
Primary care in the Wirral Health Authority.
Participants:
35 662 infants aged 1-3 months
(representing 88% of live births) and 28 768 children aged 2.9-4.0 years. 21 582 infants and children (25.1%) were excluded because of
missing or inaccurate data.
Main outcome measures:
Weight, height, sex, and age
routinely recorded by health visitors. Height, weight, and body mass
index standardised for age and sex. SD score >1.04 for body mass index
(>85th centile) was defined as overweight and >1.64 (>95th centile)
as obese. Body mass index was not calculated in infants as it is
difficult to interpret.
Results:
From 1989 to 1998 there was a highly
significant increasing trend in the proportion of overweight children
(14.7% to 23.6%; P<0.001) and obese children (5.4% to 9.2%;
P<0.001). There was also a highly significant increasing trend in the
mean SD score for weight (0.05 to 0.29; P<0.001) and body mass index (
0.15 to 0.31; P<0.001) but not height. Infants showed a small but
significantly increasing trend in mean SD score for weight (
0.17 to
0.05; P=0.005).
Conclusions:
From 1989 to 1998 there was a highly
significant increase in weight and body mass index in children under 4 years of age. Routinely collected data are valuable in identifying
anthropometric trends in populations.
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Introduction
Top
Abstract
Introduction
Participants and methods
Results
Discussion
References
![]()
Participants and methods
Top
Abstract
Introduction
Participants and methods
Results
Discussion
References
StatsDirect software was used for all statistical calculations.6 We considered calculated probabilities of
<0.05 to be significant and <0.001 to be highly significant. Summary statistics and confidence intervals are quoted here to two decimal places (original measurements included two significant digits) and
calculated probabilities to three decimal places. Mean SD scores for
height, weight, and body mass index were calculated for each year for
the 3 to 4 year age group. Mean SD scores for weight were calculated
for each year for the 1 to 3 month age group. We examined trends in
weight, height, and body mass index with Pearson's product moment
correlation for mean SD scores (weighted by the inverse of the observed
variance) and year. The robustness of inferences made with these
parametric and linear methods was explored by reanalysis with
non-linear and non-parametric alternative methods; an alternative
assumption that data exclusion constituted censorship was considered in
the reanalysis.7-9
2 trend with evenly spaced scores representing the order
in years from 1989 to 1998.10
![]()
Results
Top
Abstract
Introduction
Participants and methods
Results
Discussion
References
Figure 1 shows the mean SD scores for weight, body mass index, and
height for children over the 10 year period. If the distribution of
weights in the study and reference populations is similar, the mean SD
score from a large sample should be close to zero. We observed a
significantly increasing trend in mean SD score for weight and body
mass index between 1989 and 1998. Over the same period there was no
increasing trend in the mean SD score for height.

View larger version (16K):
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Fig 1.
Mean SD scores for weight, height, and body
mass index plotted against year of measurement for children aged 2.9 to
4 years. Increasing trend in scores significant for weight and body
mass index but not for height (Pearson's correlation (95% CI) and P
for r=0 (weighted): 0.94 (0.77 to 0.99), P<0.001; 0.93 (0.71 to 0.98), P<0.001; and 0.61 (
0.03 to 0.90), P=0.059)
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Infants
Figure 3 shows a slight increase in the mean SD scores for weight
of infants during the 10 year period. However, it was
close to zero (the 50th centile) and below zero for the whole period.
Table 2 shows the proportion of infants with a weight above the 85th
and 95th reference centiles. Throughout the study period
fewer than 15% of infants weighed above the 85th centile and fewer
than 5% above the 95th centile. During the same period there was an
increase in the number of preschool children with a weight above the
85th and 95th reference
centiles.
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Alternative analyses
Reanalysis of the data with non-linear and non-parametric methods
and assumptions did not change any of the inferences drawn.
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Discussion |
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We have found a highly significant increase in the number of overweight and obese children in the Wirral Health Authority area over the decade to 1998. In 1989 the weight and height of children in this area were similar to those of the reference population underlying the British growth reference charts, compiled in 1990.2 The increase in weight and body mass index over time has not been accompanied by an increase in height. As this was a population based study without patient identifiers we made no attempt to link the infant group to the same children measured three to four years later. However, the increase in the proportion of children above the 85th and 95th centiles for weight was not present in infants. The excessive weight gain therefore occurred between infancy and preschool age.
In adults body mass index is useful in the assessment of fatness. Concerns have been expressed regarding its use in children because it covaries with height and does not take into account the differences in the timing of growth in height and weight among various ethnic groups.11 Nevertheless, it is easy to measure and has been validated against calculations of body density. 12 13 For these reasons it has been recommended by the American Society of Clinical Nutrition and others as a reliable measurement of overweight and obese children.12 Pietrobelli et al also concluded that body mass index could be used as a measure of fatness in groups of children, although caution should be exercised in the comparison of body mass index across different age groups.13 We consider measurement of body mass index to be valid in this study because of the similar ages of the children. In addition, more than 97% of the Wirral population is of white European origin.
Definitions of overweight and obesity
There is no consensus as to the definition of overweight and obese
children. The International Obesity Task Force
suggests that children over the 80th centile are
overweight, as this corresponds to a body mass index of 25 at the age
of 18 years in men and women, which is the adult definition of
overweight.12 Our definition of overweight as being above
the 85th centile has been used by others5
but is arbitrary, and data based on the 80th centile could
be calculated easily. We agree with other authors that a consensus figure is required.
12 14
an increase in the number of
overweight and obese children and not a "normal" trend in the
population. Kotani et al found that the proportion of obese children in
their population had increased from 5% to more than 10% over two
decades.15 In our study, a similar increase occurred in 10 years.
Effects on later health
There is evidence that obesity is likely to persist into adult
life
12 15 16
and to increase the likelihood of morbidity
and mortality.17 Calle et al prospectively examined the
risk of death related to body mass index in over a million adults and
concluded that heavier men and women in all age groups had an increased
risk of death.18 Cardiovascular disease remains one of the
principal causes for this excess mortality. Increased body mass index
is also one of the important risk factors associated with the
extent of atherosclerotic lesions in the aorta and coronary arteries in
people between 2 and 39 years of age.19 Must and Strauss
reviewed the risks and consequences of obesity in childhood and
adolescence and concluded that an aggressive approach to prevention and
treatment was required.20 Early intervention, including increased activity and reduction in high fat, high calorie foods, is
important,5 and some success has been shown in such a
programme.21-23 Power et al have emphasised the
importance of population based intervention to achieve
this.24 In our study, the increase in the incidence of
obesity occurred before the age of 4 years, and interventions should be
targeted at this age group if they are to have an impact.
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What is already known on this topic
The incidence of childhood obesity is increasing and obesity is likely to persist into adult life Obesity results in considerable morbidity and mortality, of which cardiovascular disease remains one of the principal causes Interventions aimed at weight reduction must include increased physical activity as well as a reduction in consumption of high fat, high calorie foods What this study addsHeight and weight measurements taken by health visitors showed a significant increase in overweight and obese children over the decade to 1998 This increase occurred before the age of 4 years and interventions must be targeted at this age group if they are to have an impact Routinely collected data are valuable in identifying anthropometric trends in populations |
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Acknowledgments |
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Contributors: PB had the original idea for the study and carried out the initial data analysis and is guarantor. DK carried out further analysis and drafted the manuscript. IB was responsible for all the statistical analysis as well as writing the statistical methodology.
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Footnotes |
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Funding: None.
Competing interests: None declared.
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References |
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| 1. |
Reilly JJ, Dorosty AR, Emmett PM.
Prevalence of overweight and obesity in British children: cohort study.
BMJ
1999;
319:
1039 |
| 2. | Freeman JV, Cole TJ, Chinn S, Jones PRM, White EM, Preece MA. Cross sectional stature and weight reference curves for the UK, 1990. Arch Dis Child 1995; 73: 17-24[Abstract]. |
| 3. | Cole TJ, Freeman JV, Preece MA. Body mass index reference curves for the UK, 1990. Arch Dis Child 1995; 73: 25-29[Abstract]. |
| 4. | Child Growth Foundation. UK cross-sectional reference data: 1990/1. London: Child Growth Foundation, 1996. |
| 5. |
Barlow SE, Dietz WH.
Obesity evaluation and treatment: expert committee recommendations.
Pediatrics
1998;
102:
e29 |
| 6. | StatsDirect. www.statsdirect.com (accessed 15 Dec 2000). |
| 7. | Cuzick J. A Wilcoxon-type test for trend. Stat Med 1985; 4: 87-89[Medline]. |
| 8. | Conover WJ. Practical nonparametric statistics. 3rd ed. New York: Wiley, 1999. |
| 9. | Hollander M, Wolfe DA. Non-parametric statistical methods. 2nd ed. New York: Wiley, 1999. |
| 10. | Armitage P, Berry G. Statistical methods in medical research. 3rd ed. Oxford: Blackwell, 1994. |
| 11. |
Prentice AM.
Body mass index standards for children.
BMJ
1998;
317:
1401-1402 |
| 12. | Bellizzi MC, Deitz WH. Workshop on childhood obesity: summary of the discussion. Am J Clin Nutr 1999; 70: 173-15S. |
| 13. | Pietrobelli A, Faith MS, Allison DB, Gallagher D, Chiumello G, Heymsfield SB. Body mass index as a measure of adiposity among children and adolescents: a validation study. J Paediatr 1998; 132: 204-210[CrossRef][Medline]. |
| 14. |
Cole TJ, Bellizzi MC, Flegal KM, Dietz WH.
Establishing a standard definition for child overweight and obesity: international survey.
BMJ
2000;
320:
1240-1243 |
| 15. | Kotani K, Nishida M, Yamashita S, Funahashi T, Fujioka S, Tokunaga K, et al. Two decades of annual medical examinations in Japanese obese children: do obese children grow into obese adults? Int J Obes Rel Met Dis 1997; 21: 912-921[CrossRef][Medline]. |
| 16. |
Fredricks AM, Van Buuren S, Wit JM, Verloove-Vanhorick SP.
Body index measurement in 1996-7 compared with 1980.
Arch Dis Child
2000;
82:
107-112 |
| 17. |
Dietz WH.
Childhood weight affects adult morbidity and mortality.
J Nutr
1998;
128:
411-44S |
| 18. | Calle EE, Thun MJ, Petrelli JM, Rodriguez C, Heath CW. Body-mass index and mortality in a prospective cohort of US adults. New Engl J Med 1999; 341: 1098-1105. |
| 19. |
Berenson GS, Svinivasan SR, Bao W, Mewman 3rd WP, Tracy RE, Wattigney WA.
Association between multiple cardiovascular risk factors and atherosclerosis in children and young adults.
N Engl J Med
1998;
338:
1650-1656 |
| 20. | Must A, Strauss RS. Risks and consequences of childhood and adolescent obesity. Int J Obes Rel Met Dis 1999; 23(suppl 2): 2-11. |
| 21. | Luepker RV, Perry CL, McKinlay SM, Nader PR, Parcel GS, Stone EJ, et al. Outcomes of a field trial to improve children's dietary patterns and physical activity. JAMA 1996; 275: 768-776[Abstract]. |
| 22. |
Prentice AM, Jebb SA.
Obesity in Britain: gluttony or sloth?
BMJ
1995;
311:
437-439 |
| 23. |
Fruhbeck G.
Childhood obesity: time for action, not complacency.
BMJ
2000;
320:
328-329 |
| 24. |
Power C, Lake JK, Cole TJ.
Body mass index and height from childhood to adulthood in the 1958 British born cohort.
Am J Clin Nutr
1997;
66:
1094-1101 |
| 25. | NHS Executive. The National Service framework for coronary heart disease. Leeds: NHS Executive, 2000. |
(Accepted 9 November 2000)
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