distribution of body mass index categories rural and urban areas*

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1 Medycyna Wieku Rozwojowego, 2011, XV, 3, Cz. I IMiD, Wydawnictwo Aluna Beata Gurzkowska 1, Aneta Grajda 1, Zbigniew Kułaga 1, Ewelina Naieralska 1, Mieczysław Litwin 2 distribution of body mass index categories rural and urban areas* 1 Public Health Division, The Children s Memorial Health Institute, Warsaw Head of Division: Z. Kułaga, MD 2 Deartment of Research, The Children s Memorial Health Institute, Warsaw Head of Division: M. Litwin, MD, PhD Abstract Aim: To demonstrate differences in nutritional status of school-aged children and adolescents deending 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 ressure for the oulation of children and adolescents in Poland PL0080 OLAF were used in the analysis. Data were analysed by SAS. 9.2 for Windows, EiInfo 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 uils were used in the analysis: from elementary schools in urban areas, 3638 from elementary schools in s, 2792 from middle schools in urban areas and 1581 from middle schools in s. The frequency of normal weight was lower in urban comared with rural elementary schools (67.2% vs 70.0%; OR=0.88; =0.005). The frequency of underweight, overweight and obesity was higher in urban comared 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; =0.006). In the case of boys, statistically significant difference in frequency of overweight and obesity (together) was noted in urban middle schools comared to rural middle schools (16.7% vs 11.9%; OR=1.48; =0.003). In the case of girls, the frequency of underweight was lower in urban comared with rural middle schools (12.7% vs 15.9%; OR= 0.77; =0.032). Conclusions: Knowing differences in the nutritional status between uils in urban and s gives the oortunity to modify nutritional education rogrammes deending on needs identified in the articular tye of area and target grous. In urban regions, in both elementary and middle schools, boys are a risk grou for excess body weight, and require more attention in reventive undertakings. In rural areas, girls in middle schools should be targeted for reventive measures dealing with underweight. Key words: underweight, overweight, obesity, urban area, Streszczenie Cel: Ukazanie zróżnicowania stanu odżywienia dzieci i młodzieży w wieku szkolnym w zależności od lokalizacji szkoły (obszar miejski/obszar wiejski), rodzaju szkoły (odstawowa/gimnazjum) oraz łci. Materiał i metody: W racy wykorzystano wyniki badania n. Oracowanie norm ciśnienia tętniczego dla oulacji dzieci i młodzieży w Polsce PL0080 OLAF. Dane analizowano z użyciem akietu statystycznego SAS 9.2 for Windows, EiInfo oraz LMSgrowth. Wyznaczono częstość wystęowania niedowagi, nadwagi, otyłości i normy wraz z ilorazem szans (IS) w zależności od lokalizacji szkoły, rodzaju szkoły oraz łci. Wyniki: W analizie wykorzystano dane uczniów: 5118 ze szkół odstawowych na obszarach miejskich, 3638 ze szkół odstawowych na obszarach wiejskich, 2792 z gimnazjów na obszarach miej- *Acknowledgments. The OLAF study was suorted 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.

2 Distribution of body mass index categories among Polish children and adolescents from rural and urban areas 251 skich i 1581 z gimnazjów na obszarach wiejskich. W szkołach odstawowych miejskich częstość wystęowania masy ciała w normie była mniejsza niż w szkołach wiejskich (67,2% vs 70,0%; IS=0,88; =0,005), a odsetek niedowagi, nadwagi i otyłości był wyższy zarówno w gruie chłoców, jak i dziewcząt. W gimnazjach miejskich częstość wystęowania otyłości była wyższa niż w wiejskich (3,0% vs 1,6%; IS=1,88; =0,006). Wśród chłoców odnotowano istotnie wyższą częstość nadwagi i otyłości (łącznie) w gimnazjach miejskich, w orównaniu do gimnazjów wiejskich (16,7% vs 11,9%; IS=1,48; =0,003). Wśród dziewcząt częstość wystęowania niedowagi była niższa w gimnazjach miejskich, orównując do gimnazjów wiejskich (12,7% vs 15,9%; IS=0,77; =0,032). Wnioski. Poznanie różnic w stanie odżywienia uczniów z obszarów miejskich i wiejskich daje możliwość modyfikacji rogramów edukacji żywieniowej w zależności od otrzeb zidentyfikowanych na oszczególnych obszarach i gru docelowych. W regionach miejskich, zarówno w szkołach odstawowych, jak i w gimnazjach, chłocy stanowiąc gruę ryzyka związanego z nadmierną masą ciała, wymagają większej uwagi w odejmowanych działaniach rofilaktycznych. Na obszarach wiejskich dziewczęta z gimnazjów owinny być adresatami działań rofilaktycznych związanych z niedowagą. Słowa kluczowe: niedowaga, nadwaga, otyłość, obszar miejski, obszar wiejski MeD. WIekU RozWoj., 2011, XV, 3, cz IntRoDUctIon Similarly as in other countries, oor nutrition is becoming a roblem affecting children and adolescents in Poland (1, 2, 3, 4). Although the mass media usually focus on underweight in this context, esecially in the younger age grou (5), this roblem is associated rimarily with excessive body weight. This trend is articularly disturbing given the ossibility of obesity-related morbidity in adulthood as well as carrying over the health burden to the next generation (6, 7). Obesity, esecially during uberty, is increasingly being seen as an imortant factor in the future develoment of such serious diseases as hyertension, hyerliidemia, and metabolic syndrome (8, 9, 10). It is thus imortant to assess not only a child s develoment, but also to establish if obesity is resent and, if so, to what degree, which will aid in the early diagnosis of related diseases. Socioeconomic factors may lay a role in the develoment of imbalances in health, including overweight (11), which is why the influence of lace of residence and ubringing (urban/rural) on the health and develoment of children is the subject of numerous studies (12, 13, 14). In oulation 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 tye of area in which they attend school, rovides an oortunity to obtain more knowledge on the health needs of schoolaged children and adolescents, and thereby to modify health education rogrammes to address the roblems identified in the articular tye of area (urban/rural). AIM To demonstrate differences in nutritional status of school-aged children and adolescents deending on school localization (urban/rural), school level (elementary/ middle) and gender. MAteRIAl AnD MethoDs Data from the OLAF study, Elaboration of reference blood ressure ranges for Polish children and adolescents PL0080 OLAF, conducted by the Children s Memorial Health Institute (CMHI) in Warsaw in cooeration with researchers country-wide, were used in this study. The study was undertaken after obtaining the aroval of the Bioethics Committee of the CHMI. The studied oulation comrised uils who attended elementary, middle, and secondary schools in the eriod from November 2007 to November 2009; the schools were located in all of Poland s administrative districts. Selection of articiants was based on two-staged random samling. The basic samling unit was a school. The samling frame was the list of schools obtained from the Ministry of Education of Poland. In the first stage, samling was stratified (with a robability roortional to the size of the school); elementary and middle schools were stratified by urban/, secondary schools, by school tye. In the second stage, based on the size of a given school, uils were randomly selected and invited to articiate in the study. The study was conducted after obtaining written informed consent from the arents of uils under the age of 18 years and from uils who were 16 years old or older. The calendar age of the articiant 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 rotocol by trained teams using standard equiment: 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.

3 252 Beata Gurzkowska i et ws. al elementary school 35.0 middle school % % age in years 0.0 age in years elementary school age number total elementary school age number total 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. Puils age distribution in OLAF study samle of elementary and middle schools was tyical for these tyes 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 deending 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 rocessed using the SAS 9.2 for Windows statistical ackage, EiInfo 3.5.1, and LMSgrowth (downloaded from: htt://homeage.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 tye and localization. The statistical significance of differences in the frequency of underweight, normal weight, overweight, and obesity among uils of urban and rural schools was assessed by the Chi- square test for elementary and middle schools and according to gender. Differences were considered statistically significant at <0.05; those at <0.1 were considered a statistical trend. ResUlts 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 samle of uils (N=13 129), 60.2% attended schools located in urban, and 39.8% in s. Elementary school was attended by 8756 (66.7%) uils, 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 middleschool uils in urban and s were more frequent than underweight: urban 18.2% vs 12.1% (OR=1.62 <0.001); rural 16.7% vs 11.9% (OR=1.48 <0.001). Overweight and obesity were significantly more frequent among uils of schools in urban than in s (OR=1.12 =0.021), as was normal weight among rural comared with urban uils (OR=1.09 =0.036). Analysis by gender showed a significant difference in the frequencies of both overweight (15.5% vs. 13.4%; OR=1.18 =0.023) and obesity (5.0% vs. 3.9%; OR=1.29 =0.043) among boys from urban schools as comared with boys from rural ones, as well as a significantly higher frequency of normal weight among boys from s (72.1% vs 68.6%; OR=1.18 =0.003). Overweight including obesity was more frequent in elementary than in middle schools (19.7% vs 13.5%; OR=1.58 <0.001).

4 Distribution of body mass index categories among Polish children and adolescents from rural and urban areas 253 Underweight 11.2 (286) 10.9 (200) =0.767 normal weight 66.4 (1700) 0.87 ( ) = (434) 14.6 (269) 1.19 ( ) obesity 1.11 ( ) 19.6 (360) 1.19 ( ) total (1837) Underweight 12.3 (629) 11.4 (416) =0.224 normal weight 67.2 (3440) 0.88 ( ) 16.0 (819) 1.14 ( ) obesity 1.07 ( ) 1.13 ( ) total (3638 ) elementary schools The frequency of normal weight in urban elementary schools was significantly lower in comarison 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 comarison with their counterarts 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 grous 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 revalent in girls. In both tyes of schools, the ercentage of normal-weight uils 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, resectively, OR=0.81 (CI: ; =0.015) for underweight; OR=1.59 (CI: ; <0.001) for obesity; OR=1.27 (CI: ; <0.001) for overweight and obesity (jointly), whereas a statistical trend was found for overweight (OR = 1.15; CI: ; =0.064). In rural elementary schools, a significantly higher frequency of obesity was found among boys in comarison with girls (OR=1.46; CI: ; =0.023), and when overweight and obesity were analyzed jointly, a statistical trend was found (OR=1.15; CI: ; =0.093). Middle schools The ercentage of normal-weight uils 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 s. The differences were significant for both urban (OR=1.41; CI: ; <0.001) and rural (OR=1.26; CI: ; <0.001) schools. In comarison with elementary schools, in both tyes of middle schools the ercentages of overweight and obesity were smaller, and the odds ratio for occurrence of overweight including obesity in elementary schools in comarison with middle schools was, resectively, OR=1.58 (CI: ; <0.001) in urban areas and OR=1.62 (CI: ; <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 ercentage 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

5 254 Beata Gurzkowska i et ws. al. Underweight 13.4 (343) 12.0 (216) 1.14 ( ) =0.169 normal weight 68.0 (1740) 70.6 (1271) 0.89 ( ) = ( ) =0.330 obesity 3.4 (62) 1.02 ( ) = (314) 1.08 ( ) =0.338 total (1801) difference between overweight + obesity and underweight revalence (%) urban rural 2.0 elementary elementary middle middle -4.0 localization of school -3.2 schools in comarison with boys form urban schools, and a significantly higher frequency of overweight and obesity (jointly) among boys from urban middle schools. The ercentage of underweight among boys was smaller than the ercentage of overweight and obesity, in both urban and rural middle schools (tab. V). In the grou of girls, the ercentages 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 comarison with their counterarts from urban schools. A significantly higher ercentage of normal weight was found among girls from urban middle schools (tab. VI). In both rural and urban middle schools, the ercentage of underweight among girls was higher than the ercentage of overweight and obesity (fig. 2). Comarison of the frequency of normal weight, overweight, obesity, and underweight among boys and girls searately for urban and rural middle schools revealed a significant difference in the occurrence of overweight and obesity (jointly) among boys in comarison with girls from urban middle schools (OR=1.53; CI: ; =<0.001) and of underweight among girls in comarison with boys from rural middle schools (OR=1.72; CI: ; <0.001). DIscUssIon The conducted analysis of the nutritional status of uils from schools in urban and rural regions showed: a higher risk of excessive body weight among uils of urban schools as comared with their rural counterarts, a higher risk of excessive body weight in boys as comared with girls, esecially in urban areas, a lower frequency of overweight and obesity (jointly) in middle schools in comarison with elementary schools both in urban and s, a higher frequency of underweight in girls in comarison with boys, esecially in rural middle schools. The results of this analysis of the nutritional status of uils from urban and rural schools are in line with the observations of researchers articiating in the Third Anthroological Snashot of Poland Project in the 1970s who observed differences between environments in

6 Distribution of body mass index categories among Polish children and adolescents from rural and urban areas 255 Underweight 13.0 (206) 0.88 ( ) =0.177 normal weight 74.6 (1180) = (307) 10.7 (169) 1.03 ( ) obesity 1.6 (26) 1.88 ( ) 14.0 (392) 1.16 ( ) =0.112 total (2792) *yates corrected. Underweight 9.9 (76) =0.667 normal weight 72.8 (982) 12.6 (170) =0.142 obesity 1.4 (11) * 11.9 (91) 1.48 ( ) total (1349) Underweight 12.7 (183) 0.77 ( ) normal weight 10.9 (89) =0.282 obesity 2.1 (30) * 11.6 (167) 12.7 (104) 0.90 ( ) =0.410 total (1443) (816) the weight-height roortions of school-aged children from three oulations 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 oulation (7-16 years) showed that excessive body weight was significantly more frequent among uils in urban regions than in rural ones (9.4 % vs 7.1%; <0.01) (20). The study by Oblacińska et al. of 15-year-olds in Poland (as art 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 lace of residence as a factor differentiating the occurrence of excessive body weight. It was noted, however, that lace of residence did become a significant factor in underweight, which occurred more frequently in girls and urban adolescents (21). In the study by Szonar 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 ercentage of boys with a deficit of body weight in relation to height was higher in cities (13.7%) than in s (9.2%), whereas the oosite was found in girls urban vs rural: 13.9% vs 14.9%. The ercentage of overweight and obesity in urban boys was higher than in s (13.9% vs 10.8%), and in girls it was higher in s in comarison with urban (13.5% vs 10.6%) (22). These findings are in accordance with the results of our analysis. Comarison of the results of studies on the occurrence of underweight and excessive body weight is difficult because of the roblem associated with the adotion and use of uniform criteria for underweight, overweight and obesity, a comlication noted by many authors (23, 24). Nonetheless, desite this drawback, there is agreement as to the direction of changes in the adiosity of schoolaged children and adolescents(25).

7 256 Beata Gurzkowska i et ws. al. 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 rocess, in the context of consumtionism or MacDonaldization of society, affects rimarily urban oulations. In Poland, similarly to other countries, boys are articularly at risk of excess body weight (27). It may also be resumed that in Poland, the availability of fast-food and eating meals away from home affects uils of urban schools more than rural ones. A study of the eating habits of middle-school uils showed that those from s ate breakfast every morning more frequently than then their urban counterarts (58.3% vs. 56.2%, resectively; did not eat breakfast at all, 22% of urban uils, 12% of rural uils); moreover, daily consumtion of sweets was reorted more frequently in the diets of urban middle-school uils than those from s (60.4% vs 52.1%) (28). Studies conducted in the USA, Russia, and China have shown that the influence of where a erson lives on body weight may differ deending on the country. In Russia and the USA, a higher ercentage of overweight and obesity among children and adolescents was noted in s, 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 hysical activity are affecting children in both urban and s, but our analysis shows that uils from urban schools, elementary schools in articular, are at a higher risk of disordered nutritional status. conclusions Having studied the differences in the nutritional status between uils in urban and s this knowledgs gives the oortunity to modify nutritional education rogrammes deending on needs identified in the articular tye of area and target grous. 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