Distribution of body mass index categories among polish children and adolescents from rural and urban areas.*
Rozkład kategorii wskaźnika masy ciała wśród polskich dzieci i młodzieży z terenów wiejskich i miejskich
Beata Gurzkowska1, Aneta Grajda1, Zbigniew Kułaga1, Ewelina Napieralska1, Mieczysław Litwin2
1Public Health Division, The Children’s Memorial Health Institute, Warsaw
Head of Division: Z. Kułaga, MD
2Department of Research, The Children’s Memorial Health Institute, Warsaw
Head of Division: M. Litwin, MD, PhD
* Acknowledgments. The OLAF study was supported by a grant from Iceland, Liechtenstein and Norway through the EEA Financial Mechanism and the Norwegian Financial Mechanism, and the Ministry of Science and Higher Education of Poland; grant number: PL0080.
Aim: To demonstrate differences in nutritional status of school-aged children and adolescents depending on school localization (urban/rural), school level (elementary/middle) and gender.
Materials and methods: Results of current health survey ‘Elaboration of the reference range of arterial blood pressure for the population of children and adolescents in Poland’ – PL0080 OLAF were used in the analysis. Data were analysed by SAS. 9.2 for Windows, EpiInfo 3.5.1 and LMSgrowth. The frequency and the Odds Ratio of underweight, overweight, obesity and normal weight were calculated by school localization, school level and gender.
Results: Data from 13 129 pupils were used in the analysis: 5 118 from elementary schools in urban areas, 3638 from elementary schools in rural areas, 2792 from middle schools in urban areas and 1581 from middle schools in rural areas. The frequency of normal weight was lower in urban compared with rural elementary schools (67.2% vs 70.0%; OR=0.88; p=0.005). The frequency of underweight, overweight and obesity was higher in urban compared with rural elementary schools, both boys and girls. The frequency of obesity was higher in urban middle schools than rural (3.0% vs 1.6%; OR=1.88; p=0.006). In the case of boys, statistically significant difference in frequency of overweight and obesity (together) was noted in urban middle schools compared to rural middle schools (16.7% vs 11.9%; OR=1.48; p=0.003). In the case of girls, the frequency of underweight was lower in urban compared with rural middle schools (12.7% vs 15.9%; OR= 0.77; p=0.032).
Conclusions: Knowing differences in the nutritional status between pupils in urban and rural areas gives the opportunity to modify nutritional education programmes depending on needs identified in the particular type of area and target groups. In urban regions, in both elementary and middle schools, boys are a risk group for excess body weight, and require more attention in preventive undertakings. In rural areas, girls in middle schools should be targeted for preventive measures dealing with underweight.
Key words: underweight, overweight, obesity, urban area, rural area
Cel: Ukazanie zróżnicowania stanu odżywienia dzieci i młodzieży w wieku szkolnym w zależności od lokalizacji szkoły (obszar miejski/obszar wiejski), rodzaju szkoły (podstawowa/gimnazjum) oraz płci.
Materiał i metody: W pracy wykorzystano wyniki badania pn. „Opracowanie norm ciśnienia tętniczego dla populacji dzieci i młodzieży w Polsce” – PL0080 OLAF. Dane analizowano z użyciem pakietu statystycznego SAS 9.2 for Windows, EpiInfo 3.5.1 oraz LMSgrowth. Wyznaczono częstość występowania niedowagi, nadwagi, otyłości i normy wraz z ilorazem szans (IS) w zależności od lokalizacji szkoły, rodzaju szkoły oraz płci.
Wyniki: W analizie wykorzystano dane 13 129 uczniów: 5118 ze szkół podstawowych na obszarach miejskich, 3638 ze szkół podstawowych na obszarach wiejskich, 2792 z gimnazjów na obszarach miejskich i 1581 z gimnazjów na obszarach wiejskich. W szkołach podstawowych miejskich częstość występowania masy ciała w normie była mniejsza niż w szkołach wiejskich (67,2% vs 70,0%; IS=0,88; p=0,005), a odsetek niedowagi, nadwagi i otyłości był wyższy zarówno w grupie chłopców, jak i dziewcząt. W gimnazjach miejskich częstość występowania otyłości była wyższa niż w wiejskich (3,0% vs 1,6%; IS=1,88; p=0,006). Wśród chłopców odnotowano istotnie wyższą częstość nadwagi i otyłości (łącznie) w gimnazjach miejskich, w porównaniu do gimnazjów wiejskich (16,7% vs 11,9%; IS=1,48; p=0,003). Wśród dziewcząt częstość występowania niedowagi była niższa w gimnazjach miejskich, porównując do gimnazjów wiejskich (12,7% vs 15,9%; IS=0,77; p=0,032).
Wnioski. Poznanie różnic w stanie odżywienia uczniów z obszarów miejskich i wiejskich daje możliwość modyfikacji programów edukacji żywieniowej w zależności od potrzeb zidentyfikowanych na poszczególnych obszarach i grup docelowych. W regionach miejskich, zarówno w szkołach podstawowych, jak i w gimnazjach, chłopcy stanowiąc grupę ryzyka związanego z nadmierną masą ciała, wymagają większej uwagi w podejmowanych działaniach profilaktycznych. Na obszarach wiejskich dziewczęta z gimnazjów powinny być adresatami działań profilaktycznych związanych z niedowagą.
Słowa kluczowe: niedowaga, nadwaga, otyłość, obszar miejski, obszar wiejski
Similarly as in other countries, poor nutrition is becoming a problem affecting children and adolescents in Poland (1, 2, 3, 4). Although the mass media usually focus on underweight in this context, especially in the younger age group (5), this problem is associated primarily with excessive body weight. This trend is particularly disturbing given the possibility of obesity-related morbidity in adulthood as well as carrying over the health burden to the next generation (6, 7). Obesity, especially during puberty, is increasingly being seen as an important factor in the future development of such serious diseases as hypertension, hyperlipidemia, and metabolic syndrome (8, 9, 10). It is thus important to assess not only a child’s development, but also to establish if obesity is present and, if so, to what degree, which will aid in the early diagnosis of related diseases. Socioeconomic factors may play a role in the development of imbalances in health, including overweight (11), which is why the influence of place of residence and upbringing (urban/rural) on the health and development of children is the subject of numerous studies (12, 13, 14).
In population and screening studies, the body mass index (BMI) is a measure of nutritional status. Evaluation of the differences in nutritional status among children and adolescents based on the BMI and type of area in which they attend school, provides an opportunity to obtain more knowledge on the health needs of schoolaged children and adolescents, and thereby to modify health education programmes to address the problems identified in the particular type of area (urban/rural).
To demonstrate differences in nutritional status of school-aged children and adolescents depending on school localization (urban/rural), school level (elementary/ middle) and gender.
MATERIAL ND METHODS
Data from the OLAF study, “Elaboration of reference blood pressure ranges for Polish children and adolescents” PL0080 OLAF, conducted by the Children’s Memorial Health Institute (CMHI) in Warsaw in cooperation with researchers country-wide, were used in this study. The study was undertaken after obtaining the approval of the Bioethics Committee of the CHMI. The studied population comprised pupils who attended elementary, middle, and secondary schools in the period from November 2007 to November 2009; the schools were located in all of Poland’s administrative districts. Selection of participants was based on two-staged random sampling. The basic sampling unit was a school. The sampling frame was the list of schools obtained from the Ministry of Education of Poland. In the first stage, sampling was stratified (with a probability proportional to the size of the school); elementary and middle schools were stratified by urban/rural area, secondary schools, by school type. In the second stage, based on the size of a given school, pupils were randomly selected and invited to participate in the study. The study was conducted after obtaining written informed consent from the parents of pupils under the age of 18 years and from pupils who were 16 years old or older. The calendar age of the participant was calculated as the difference between the date of the examination and the date of birth. The result was recorded in the decimal system and the middle of the range was taken as the calendar age (e.g. children in the range ?11.5 and <12.5 years are 12 years old). Body height and weight measurements were taken in accordance with the OLAF study protocol by trained teams using standard equipment: a SECA 214 (Germany) stadiometer and a WPT100/200 electronic medical scale (Radwag, Poland) (15). Arithmetic averages of 2 or 3 height and weight measurements were analyzed; the BMI was calculated using the formula: BMI = body weight (kg)/body height (m)2.
The data was analyzed by school localization (urban/rural), school level (elementary/middle), and gender. Due to the low number of secondary schools located in rural areas, only elementary and middle schools were included in the analysis. Pupils’ age distribution in OLAF study sample of elementary and middle schools was typical for these types of schools in Poland (fig. 1). The localization of a school (urban/rural) was determined according to the Central Statistical Office in accordance with the December 15, 1998 Council of Ministers Directive establishing the official national register of the territorial division of Poland (TERYT) (16). Overweight and obesity were determined depending on gender and age using the BMI cutoffs characterized by the International Obesity Task Force (IOTF) (17), whereas underweight was determined using the BMI cutoffs according to Cole TJ et al. (18). Normal weight was declared in a child who was neither underweight nor overweight including obesity. The data were processed using the SAS 9.2 for Windows statistical package, EpiInfo 3.5.1, and LMSgrowth (downloaded from: http://homepage.mac.com/tjcole/FileSharing1.html). The frequency of underweight, normal weight, overweight, and obesity, as well as the odds ratio (OR) with a 95% confidence interval (CI) were determined for gender, school type and localization. The statistical significance of differences in the frequency of underweight, normal weight, overweight, and obesity among pupils of urban and rural schools was assessed by the Chisquare test for elementary and middle schools and according to gender. Differences were considered statistically significant at p<0.05; those at p<0.1 were considered a statistical trend.
The analysis of the nutritional status of children and adolescents was conducted on the data obtained from 210 elementary schools (59 urban and 151 rural) and 86 middle schools (54 urban and 32 rural). In the analyzed sample of pupils (N=54 129) 60.2% attended schools located in urban, and 39.8% in rural areas. Elementary school was attended by 8756 (66.7%) pupils, middle school by 4373 (33.3%), among whom boys constituted 50.2% in elementary and 48.3% in middle schools.
Overweight including obesity among elementary and middle-school pupils in urban and rural areas were more frequent than underweight: urban 18.2% vs 12.1% (OR=1.62 p<0.001); rural 16.7% vs 11.9% (OR=1.48 p<0.001). Overweight and obesity were significantly more frequent among pupils of schools in urban than in rural areas (OR=1.12 p=0.021), as was normal weight among rural compared with urban pupils (OR=1.09 p=0.036). Analysis by gender showed a significant difference in the frequencies of both overweight (15.5% vs. 13.4%; OR=1.18 p=0.023) and obesity (5.0% vs. 3.9%; OR=1.29 p=0.043) among boys from urban schools as comapred with boys from rural ones, as well as a significantly higher frequency of normal weight among boys from rural areas (72.1% vs 68.6%; OR=1.18 p=0.003). Overweight including obesity was more frequent in elementary than in middle schools (19.7% vs 13.5%; OR=1.58 p<0.001).
The frequency of normal weight in urban elementary schools was significantly lower in comparison with rural schools, and the frequency of overweight, obesity, and underweight was higher, with the frequency of overweight being statistically significant, as were overweight and obesity when analyzed jointly. In both urban and rural elementary schools, the frequencies of overweight and obesity were higher than of underweight (tab. I). Analysis by gender showed a significantly higher frequency of both overweight and obesity (analyzed jointly) among boys from urban elementary schools in comparison with their counterparts from rural schools. Boys attending rural elementary schools were found, in turn, to be of normal weight significantly more frequently than boys from urban elementary schools. The frequencies of overweight and obesity were higher than of underweight in the groups of boys and girls in both urban and rural schools. The difference between the frequency of excessive body weight (overweight and obesity) and underweight among boys from urban schools was over double that in girls (tab. II, tab. III, fig. 2). In both urban and rural elementary schools, overweight and obesity affected boys more than girls, whereas underweight was more prevalent in girls. In both types of schools, the percentage of normal-weight pupils was slightly higher in girls than in boys. In urban elementary schools, significant differences in the frequency of underweight, overweight, and obesity were found, with the boys/girls odds ratio equaling, respectively, OR=0.81 (CI: 0.68-0.96; p=0.015) for underweight; OR=1.59 (CI: 1.20-2.10; p<0.001) for obesity; OR=1.27 (CI: 1.10-1.46; p<0.001) for overweight and obesity (jointly), whereas a statistical trend was found for overweight (OR = 1.15; CI: 0.99-1.34; p=0.064). In rural elementary schools, a significantly higher frequency of obesity was found among boys in comparison with girls (OR=1.46; CI: 1.04- 2.06; p=0.023), and when overweight and obesity were analyzed jointly, a statistical trend was found (OR=1.15; CI: 0.97-1.37; p=0.093).
The percentage of normal-weight pupils was higher in middle schools than in elementary schools in both urban and rural settings. The difference in relation to elementary schools was 7.1% in urban areas and 4.6% in rural areas. The differences were significant for both urban (OR=1.41; CI: 1.27-1.57; p<0.001) and rural (OR=1.26; CI: 1.10- 1.44; p<0.001) schools. In comparison with elementary schools, in both types of middle schools the percentages of overweight and obesity were smaller, and the odds ratio for occurrence of overweight including obesity in elementary schools in comparison with middle schools was, respectively, OR=1.58 (CI: 1.39-1.79; p<0.001) in urban areas and OR=1.62 (CI: 1.36-1.93; p<0.001) in rural ones. The frequency of obesity was significantly higher in urban middle schools than in rural ones, whereas the frequency of overweight was similar in urban and rural middle schools. A smaller percentage of underweight was found in urban middle schools (statistically nonsignificant) (tab. IV). In the analysis by gender, a significantly higher share of normal weight was found among boys from rural middle schools in comparison with boys form urban schools, and a significantly higher frequency of overweight and obesity (jointly) among boys from urban middle schools. The percentage of underweight among boys was smaller than the percentage of overweight and obesity, in both urban and rural middle schools (tab. V).
In the group of girls, the percentages of overweight and obesity and of underweight were smaller in urban middle schools. A significant difference was found between the frequency of underweight among girls from rural middle schools in comparison with their counterparts from urban schools. A significantly higher percentage of normal weight was found among girls from urban middle schools (tab. VI). In both rural and urban middle schools, the percentage of underweight among girls was higher than the percentage of overweight and obesity (fig. 2).
Comparison of the frequency of normal weight, overweight, obesity, and underweight among boys and girls separately for urban and rural middle schools revealed a significant difference in the occurrence of overweight and obesity (jointly) among boys in comparison with girls from urban middle schools (OR=1.53; CI: 1.23-1.91; p=<0.001) and of underweight among girls in comparison with boys from rural middle schools (OR=1.72; CI: 1.26- 2.35; p<0.001).
The conducted analysis of the nutritional status of pupils from schools in urban and rural regions showed:
– a higher risk of excessive body weight among pupils of urban schools as compared with their rural counterparts,
– a higher risk of excessive body weight in boys as compared with girls, especially in urban areas,
– a lower frequency of overweight and obesity (jointly) in middle schools in comparison with elementary schools both in urban and rural areas,
– a higher frequency of underweight in girls in comparison with boys, especially in rural middle schools.
The results of this analysis of the nutritional status of pupils from urban and rural schools are in line with the observations of researchers participating in the Third Anthropological Snapshot of Poland Project in the 1970s who observed differences between environments in the weight-height proportions of school-aged children from three populations residing in areas differing in the degree of urbanization (major cities, small towns, rural villages) (19). Similarly, in the 1990s an analysis of the frequency of overweight and obesity in the schoolaged population (7-16 years) showed that excessive body weight was significantly more frequent among pupils in urban regions than in rural ones (9.4 % vs 7.1%; p<0.01) (20). The study by Oblacinska et al. of 15-year-olds in Poland (as part of the international HBSC study) showed a significant difference in the occurrence of overweight and obesity – more frequent among boys than girls, but did not identify place of residence as a factor differentiating the occurrence of excessive body weight. It was noted, however, that place of residence did become a significant factor in underweight, which occurred more frequently in girls and urban adolescents (21). In the study by Szponar et al. on the nutritional status of children and adolescents aged 1 to 18 years, based on body weight-to-height centile charts for Warsaw children, it was found that the total percentage of boys with a deficit of body weight in relation to height was higher in cities (13.7%) than in rural areas (9.2%), whereas the opposite was found in girls – urban vs rural: 13.9% vs 14.9%. The percentage of overweight and obesity in urban boys was higher than in rural areas (13.9% vs 10.8%), and in girls it was higher in rural areas in comparison with urban (13.5% vs 10.6%) (22). These findings are in accordance with the results of our analysis.
Comparison of the results of studies on the occurrence of underweight and excessive body weight is difficult because of the problem associated with the adoption and use of uniform criteria for underweight, overweight and obesity, a complication noted by many authors (23, 24). Nonetheless, despite this drawback, there is agreement as to the direction of changes in the adiposity of schoolaged children and adolescents(25).
Sobal (26), commenting on the study by Wang (27), sees the source of the higher risk of obesity in the changing of living standards related to globalization. This process, in the context of consumptionism or MacDonaldization of society, affects primarily urban populations. In Poland, similarly to other countries, boys are particularly at risk of excess body weight (27). It may also be presumed that in Poland, the availability of fast-food and eating meals away from home affects pupils of urban schools more than rural ones. A study of the eating habits of middle-school pupils showed that those from rural areas ate breakfast every morning more frequently then their urban counterparts (58.3% vs. 56.2%, respectively; did not eat breakfast at all, 22% of urban pupils, 12% of rural pupils); moreover, daily consumption of sweets was reported more frequently in the diets of urban middle-school pupils than those from rural areas (60.4% vs 52.1%) (28). Studies conducted in the USA, Russia, and China have shown that the influence of where a person lives on body weight may differ depending on the country. In Russia and the USA, a higher percentage of overweight and obesity among children and adolescents was noted in rural areas, whereas in China, a higher risk of excessive body weight was found in cities (13, 27).
It seems that in Poland, unfavorable changes in lifestyle in terms of eating and physical activity are affecting children in both urban and rural areas, but our analysis shows that pupils from urban schools, elementary schools in particular, are at a higher risk of disordered nutritional status.
Having studied the differences in the nutritional status between pupils in urban and rural areas this knowledgs gives the opportunity to modify nutritional education programmes depending on needs identified in the particular type of area and target groups. In urban regions, in both elementary and middle schools, boys are a risk group for excess body weight, and require more investments in preventive undertakings. In rural areas, girls in middle schools should be targeted for preventive measures dealing with underweight.
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Adres do korespondencji / Address for correspondence:
The Children’s Memorial Health Institute
Public Health Division
Al. Dzieci Polskich 20, 04-730 Warsaw
tel.: (+48 22) 815-19-45