Current WHO recommendations for adolescent anthropometry

Description of WHO recommendations
Application of the WHO recommendations

Description of WHO recommendations

(SUMMARISED FROM: PHYSICAL STATUS: THE USE AND INTERPRETATION OF ANTHROPOMETRY, REPORT OF A WHO EXPERT COMMITTEE ¹²)

(1) To screen adolescents for severe undernutrition to determine the need for admission to therapeutic feeding:

Use clinical criteria. Visual evidence of extreme emaciation can identify those requiring immediate feeding. The ability to walk or work may also be important in identifying those in greatest need. Pregnant and lactating adolescents may need additional nutritional support.

Use BMI-for-age to assess acute undernutrition. Each measured adolescent's BMI is compared to members of the same age and sex in the National Center for Health Statistics (NCHS) reference population consisting of adolescents in the United States who were measured as a part of the first National Health and Nutrition Examination Survey (NHANES I) in 1971-1974 ^{24, 25}. [Note that CDC has recently published new growth charts based on children from the US, see www.cdc.gov/nchs.]

Adolescents falling below the 5th centile of the NCHS reference population may need intervention, although local cut-offs can also be developed which take into account the availability of resources to manage the patient load.

Because of major differences between boys and girls in the timing of maturational events (including the growth spurt) separate references must be used for each sex.

Use BMI-for-age as described above. Calculate the proportion of adolescents falling below the 5th centile or a locally-defined cut-off point.

Compare the height of each adolescent to the height of adolescents of the same sex and age in the NCHS reference population. Adolescents falling below the 3rd centile of the NCHS reference population are defined as stunted²⁶.

Along with weight, height, and age, survey workers should collect data on specific landmarks of sexual maturation. For each female adolescent, the Tanner breast stage and the age of menarche (if postmenarcheal) should be collected. For male adolescents, the Tanner genitalia stage and the age of attainment of adult voice should be collected. For female adolescents, investigators then calculate the median age of reaching the Tanner breast stage 2 and the median age of menarche. For male adolescents investigators calculate the median age of attaining the Tanner genitalia stage 3 and median age of attaining adult voice.

The difference is calculated between the survey population and the reference population in the median ages of attaining these landmarks. For each sex, the differences for the two landmarks are averaged.

For each sex separately, the average difference between the survey and reference populations in these median ages is then used to adjust the age of each survey subject. (See Box 2 for example of adjustment for maturational age in females.)

Application of the WHO recommendations

Since their publication, the WHO recommendations have been used to analyse the results of several surveys undertaken in both stable and displaced populations in developing countries. The survey population characteristics and the estimated prevalence rates of thinness and stunting are summarised in Table 1.

Table 1 Summary of the results of surveys which used WHO recommendations to assess adolescent nutritional status

Reference	Camp or population	Date or survey	Age of survey subjects (years)	Number of survey subjects	Socioeconomic level of subjects	Prevalence of low BMI (thinness) <5th centile	Prevalence of low height-for-age(stunting) <5th centile
Stable populations
5	Schoolgirls in Dhaka, Bangladesh	May - Aug 1995	10-16	384 females	Literacy: 98% fathers 95% mothers	16%	10%
27	Schoolboys in Calcutta, India	1982-83	10-16	570 males	³10 years school: 82% fathers 64% mothers	52%	12%
28	School students in Bombay, India	1992-93	10-19	69 males 69 females	Residents of urban slums	53%	32%
28	Residents of 3 rural villages in Nepal	1992-93	10-18	179 males 148 females	"lower-income areas"	36%	47%
28	Residents of 4 rural villages in Benin	1992-93	12-18	179 males 171 females	"lower-income areas"	23%	41%
Displaced populations
29	School attendees, Kakuma camp, Kenya	April 1997	Males: 9-20 Females: 9-17	1011 males 320 females	Refugees dependent on food aid	Boys: 75% Girls: 55%	N.A.
30	Population-based sample, Kakuma camp, Kenya	November 1998	10-19	265 males 124 females	Refugees dependent on food aid	57%	9%
31	Population-based sample, 3 camps in Dadaab District, Kenya	November 1998	10-19	208 males 184 females	Refugees dependent on food aid	61%	22%
32	Population-based sample, 7 camps in Nepal	October 1999	10-19	225 males 238 females	Refugees dependent on food aid	Crude: 36% Adjusted*: 34%	Crude: 67% Adjusted*: 55%

* Adjusted for differences in age of sexual maturation between survey and reerence populations

Although no data were specifically collected on health outcomes, four of the surveys chose samples from among children who were well enough to attend school during survey activities. Nonetheless, three of these surveys estimated that the prevalence of thinness (indicating undernutrition) was greater than 50%. In the three refugee camp surveys that collected additional health data, there was no evidence of elevated morbidity or mortality in these populations ^30-32.

Two of the surveys included adolescents from families with relatively high socioeconomic status and yet still found substantial acute undernutrition among adolescents.

In three surveys undertaken in refugee camps, monitoring showed that the amount of food contained in the general distribution was generally adequate ^30-32. One would have to hypothesize extraordinarily inequitable intra-household food distribution to explain the high prevalence of acute undernutrition among adolescents if the survey results are valid.

In the refugee camp surveys there were no indications, other than the results of the adolescent surveys, that substantial undernutrition existed in any segment of the population. In all these populations, recent surveys of children less than 5 years of age had estimated a low prevalence of acute undernutrition ^29-32.

Eight surveys estimate the prevalence of both thinness and stunting. In five of these surveys, the estimated prevalence of thinness exceeded that of stunting by a factor of 1.6 - 6.3. Although little is known about the usual ratio of the prevalence rates of thinness and stunting among nutritionally compromised adolescents, these results would be highly unusual in children up to 5 years of age. An analysis of the results of 175 nutrition surveys throughout the world demonstrated that among children 12-23 months of age, stunting was 2.5-12.5 times more common that thinness, depending on the region where the survey was done ³³. In addition, in the WHO Global Database on Child Growth and Malnutrition, only Fiji has a higher prevalence of thinness than of stunting ³⁴. Although the applicability of these data to adolescents is not precisely known, one might expect that in adolescents - as for young children - the prevalence of stunting would exceed the prevalence of thinness because stunting is cumulative, while thinness is due to relatively recent undernutrition.