Weight and Height of Saudi Children Six to 16 Years from the Eastern Province

Introduction

Periodic studies of growth of children serve a number of important objectives. They provide information on the nutritional status of children at a given point in time, on secular trends over a span of time, and support regional, national, and international comparisons. They also enable health workers to identify populations, age groups, and areas needing strengthening of nutritional and related services.

The Eastern Province, like the rest of the Kingdom, has seen rapid economic growth in recent years. Parallel with this, the population of children from birth to adolescence has rapidly expanded. Reports on growth of children are limited. Only one large series has recently been published in respect to growth status of school age children in the Kingdom ^[1], and a few studies have been carried out in infants and preschool children ^[2,3]. An effort has, therefore, been made in this study to assess the weight and height of a large sample of children ages six to 16 years in the Eastern Province, the objective being to provide information on their weight and height status, sex differences, and to make available baseline data for future comparisons of secular trends. We also wished to see how these children compared with the international standards ^[4].

MATERIAL AND METHODS

Sample Design: This study, initially with a survey, was carried out in the Eastern Province of the Kingdom of Saudi Arabia, covering four districts, including both rural and urban population; namely Dammam, Al-Khobar (including Thoqba and Dhahran), Qatif and Al-Hassa. The sample was designed to provide separate estimates for height and weight for each single age from six through 16 years for both males and females. The four school districts and the two sexes were used as eight sampling strata.

A two-stage stratified cluster sample was selected. The sampling units at the first stage were government schools. The frame for the selection of the primary sampling units was based on a list provided by educational authorities in the Eastern Province. Schools with less than nine classes were identified and combined with the nearest school to form a school unit. Total number of students in each school was used as a weighting factor for the first stage sampling. The second stage was classes within the schools. Each class was considered as a cluster and all students in selected classes were included in the study. Sample size calculation required the selection of 14 boys’ schools and 14 girls’ schools in each of the four districts. A total of 21,638 Saudi children, free from any physical handicaps, were weighed and their height measured (10,731 boys and 10,907 girls).

Before the study was begun, the principal investigator met the school authorities, explained the purpose of the study, and sought their consent. Agreement was reached on conducting the study, with due regard for Islamic ethics and local customs, and parents’ wishes. Trained teams consisting of postgraduate doctors and pediatric nursing personnel were then sent on preplanned schedules of visits at the convenience of the school authorities with the least disturbance to the pupils. They had adequate prior experience of weighing children and were properly briefed for purposes of the study with emphasis on need for accuracy and agreement between observers. After measurements were taken by the trained workers under supervision of an expert, a recheck of the same children was carried out at the next visit within a week or two by the supervisor. Final entries of measurements were made only after ensuring that the measurements were accurate. The study was begun in 1988 and completed in 1990.

TECHNIQUES

Weight: Children were weighed barefoot with boys in underclothes, and girls in a light gown as per local custom. The weighing scale used was Seca lever type (made in Germany) which could read to the nearest 100 g. It was calibrated at the beginning of each working day. Taring was done at each weighing.

Height: Height was measured to the nearest 0.1 cm using the measuring rod attached to the same weighing scale with a sliding headpiece. The child stood on the platform with heels touching and feet at an angle of 45 degrees. Heels, buttocks, shoulders, and occiput were made to touch the vertical rod. The head was held erect with external auditory meatus and the lower border of the orbit in one horizontal plane. The headpiece was then lowered until it made light contact with the hair and the reading was taken. Readings were always taken before 11 a.m.

Age Determination: Since age is the crucial variable of the study, every effort was made to record this reliably. School records, mostly by birth certificates entered at the time of school admission, were used as being accurate. “Completed years” were recorded: for example, the children from age nine to nine years and eleven months (i.e., before their next birthday) were recorded as nine years, etc.

Schools and parents in the Kingdom record ages according to Hegira calendar based on the lunar year. The Hegira year is shorter than the Gregorian by 11 days, so that a child is 11 days older by the Gregorian year. Due note was taken of this fact in the analysis, and the graphs indicate ages by both, for the convenience of readers. It is important to mention here the fact that ages of Saudi children, recorded by the Hegira calendar and plotted on international reference standards, puts them at a disadvantage. For instance, a child age 16 years by the Hegira calendar is in fact around 15.5 years by the “365-day” year (16x11=176). Such a child is thus likely to be erroneously compared with one six months older on the reference standard if this necessary arithmetic correction is ignored. A brief communication adapting the National Center for Health Statistics (NCHS) reference chart for weight and height to the Hegira year appears elsewhere ^[5], and is recommended for use in Saudi Arabia and other countries using the Hegira calendar. In the present study, all ages are represented in Hegira years. The NCHS values are also adapted to the same to enable valid comparisons. Distance growth curves of selected percentiles for boys and girls in respect to weight and height were drawn (Figures 1-4). These were compared with those of the NCHS (which are used in this region as reference standards for want of an alternative indigenous standard) (Figures 5 and 6).

STATISTICAL METHODS

Data were entered on an IBM-compatible personal computer, and “EPI Info” STATISTICAL package was used to calculate selected percentiles, mean and standard deviation (SD) for each single age six to 16 years for both genders ^[7].

RESULTS

The total number was 21,638: 10,731 boys (49.6%) and 10,907 girls (50.4%). Tables 1 and 2 give their distribution by age and sex included in the study together with the percentiles, mean and SD for weight and height. Except at the extremes of age, over 1,300 pupils were measured at each age. Not less than 800 were taken, even at the extremes of age (six and 16). The number of children included in this study represent over 10% of the total school population between six and 16 years of age in the Eastern Province from which the sample was drawn. From the statistical point of view, therefore, the number studied would produce minimal sampling error.

Table 1. Smoothed percentiles, mean, and standard deviation of weight in kilograms of six-16 years-of-age (Hegira years) of Saudis living in the Eastern Province.

Table 2. Smoothed percentiles, mean, and standard deviation of height in centimeters of six-16 years-of-age (Hegira years) of Saudis living in the Eastern Province.

Weight for Age:Figures 1 and 2 show the distance weight curves in the tenth, 25th, 50th, 75th and 90th percentiles in boys and girls. In the 90th percentile, girls were heavier than boys throughout (from seven to 16 years). In the 50th and tenth percentiles, boys were marginally heavier than girls before nine and 11 years, respectively. Beyond these points (seven years in the 90th, nine years in the 50th, and 11 years in the tenth percentiles), the contrast between the sexes increased proportionately in favor of girls, with higher percentiles until above 16 years. The difference in mean weights between sexes was statistically significant between ages ten and 15 years (P <0.005).

Height for Age:Figures 3 and 4 show the distance height curves for boys and girls in the tenth, 25th, 50th, 75th and 90th pecentiles. Before the ages of 9.5, 10, and 11 years in the 90th, 50th and tenth percentiles, respectively, the contrast in height favored boys. Beyond these age points, the contrast in favor of girls increased with diminishing percentiles until ages 13, 13.75, and 15 years, when the curves for girls flattened out, but those for boys continued to rise steeply. These observations were found to be statistically significant (P <0.0005) at all ages.

Weight and height of NCHS children were compared with children in the present study. For this purpose, the NCHS weight/height percentiles were adapted to ages in Hegira years.

DISCUSSION

We present results of a cross-sectional study of weight and height of 21,638 Saudi boys and girls of school age, six to 16 years, from the Eastern Province (EP) carried out between 1988 and 1990. It is appreciated that longitudinal or semilongitudinal studies provide more precise information of growth of children than do cross-sectional. However, a larger sample would considerably offset many disadvantages of such a study. Tanner ^[6] has suggested methods of constructing even velocity growth curves from cross-sectional studies, although they are less reliable. Literature from the Kingdom is largely confined to infants and preschool children ^[2,3], and the authors are aware of only one study in schoolchildren ^[1]. We stress the fact that Saudi children, whose ages are recorded in Hegira years, are at a disadvantage when compared to international standards (such as the NCHS as an example), in view of the shorter Hegira year compared to the Gregorian. The NCHS curves have, therefore, been adapted to the Hegira year to enable comparison with the present study ^[4,5]. If, for want of an indigenous reference standard, NCHS values are used, the adapted NCHS chart is recommended for clinical use in countries using the Hegira year. For the same reason, precise comparison of the present study with those using the Gregorian year is not possible, although general observations on obvious findings can be compared ^[8-12].

Saudi girls were heavier than boys after the seventh year in the 90th, ninth year in the 50th, and the 11th year in the tenth percentiles. Before these ages, boys were heavier and this fact is well known. Saudi girls maintained this advantage almost until 16 years of age, unlike NCHS where boys “overtake” girls by the 14th year. In spite of comparatively lower weights among Saudi children, Saudi girls between 12 and 14 years at the 50th percentile were as heavy as NCHS girls - even marginally heavier. Al-Sekait et al study from Riyadh ^[1] appears to conform to these findings, although no mention has been made in that study about the manner of age determination from the Hegira calendar. We considered the possibility of girls, particularly 12 to 14 years from affluent families, having been included in the present study in sufficiently large numbers to explain this result, but this was ruled out since the distribution was observed to be fairly uniform. It appears, therefore, that the reason is sociocultural. In this part of the world, girls at this age have restricted physical activity compared with Western girls, who are usually engaged in strenuous games and sports activities both inside and outside their homes. This fact is corroborated in an Egyptian study ^[10]. Apart from less strenuous physical exercise, genetic and environmental factors have been suggested ^[1], although these factors are unlikely to be operative in a very restricted age range (12 to 14 years only in the present study). Observations indicate that growth continues beyond 16 years in Saudi boys as is evident from the steep rise in curves for both height and weight. In girls, curves for height tend to flatten out but for weight, continue to rise, particularly in higher percentiles.

In terms of height, the “normal” pattern, such as that of the NCHS study, is as follows: little difference in sexes until about the age of ten years, girls taller until about 14 years, and boys once again overtaking girls thereafter. With their greater peak height velocity and more prolonged height spurt, boys end up being ultimately taller. Saudi children in the 90th percentile followed this pattern more closely than those in the tenth. These differences reflect the influence of nutrition and environment, the more advantaged (higher percentiles) conforming more closely to the NCHS values.