(1.68 and 96% Cl: 1.46-1.94) than among sons of Swedish mothers. Conclusions: The ... Epidemiology, Karolinska University Hospital, S-171 76 Stockholm,. Sweden, tel. ... America including Australia, New Zealand and Israel, and excluding ...
S H O R T
R E P O R T S
Ethnic differences in being overweight and obesity among male military conscripts born in Sweden between 1973 and 1975 C.E. MICHAEL OLDENBURG, NIKI U. COTTEN-OLDENBURG, FINN RASMUSSEN *
Background: Ethnic differences in being overweight and obesity were studied among 18 year old males in Sweden. Methods. This nationwide study was based on a record linkage between the Medical Birth Register, the Register of Military Induction Examinations and the Register of the Total Population. For 140,766 (87.8%) of the 160,247 males information was available on body mass index (BMI) and on their mothers' nationality. Results. After adjustment for education and geographical region the odds ratio for being overweight was found to be higher among 18 year old sons of immigrants from Finland (1.38 and 95% Cl: 1.26-1.52) than among sons of Swedish mothers. Similarly, the odds ratio for being overweight was higher among the sons of immigrants from former Eastern Europe (1.68 and 96% Cl: 1.46-1.94) than among sons of Swedish mothers. Conclusions: The risks of being overweight and obesity were increased among the sons of immigrants from Finland and former Eastern Europe compared to sons of Swedish mothers.
Keywords: ethnicity, obesity, overweight, young men
o
Stockholm metropolitan area, all other geographical rebesity is an important public health problem in the gions in Sweden had significantly higher BMIs and an Western World. In the US, a recent study showed that inverse relationship was demonstrated between populaoverweight prevalence estimates have increased in all tion density and BMIs. Odier studies in die US have race and sex groups. Approximately 33% of adults 20 years shown that BMI among young adults differs by race, sex, of age and older in the US were overweight during the age, income and educational level.10 period 1988-1991.1 Recent studies in Sweden found that Immigrant etlinic groups provide interesting data for inthe prevalence of being overweight increased consistently ternational studies on the influences of predominating in all age and socioeconomic groups during the 1980s.2"4 populations on minority populations. Some international Other European studies have also found increases in the studies have shown a higher prevalence of being overprevalence of overweight over time in Great Britain,5 weight among ethnic minorities when compared to the Finland,6 and The Netherlands.7 majority population group.1'2 In Sweden, for example, Body mass index (BMI), calculatedfrombody weight (kg) native-born Swedish men aged 16—84 years have a signidivided by the square of height (m ) is the index of choice ficantly lower mean BMI than all other ethnic groups.2 for large-scale epidemiologic studies on being overweight In the light of these findings this epidemiologic study was and previous research has shown that BMI is a useful conducted to investigate potential ethnic differences in index for comparing different population groups.8'9 BMI among male military conscripts born in Sweden Two recent studies in Sweden demonstrated that level of between 1973 and 1975. education and geographical region significantly influence the prevalence of being overweight and obesity.2*3 Swedish men with a higher level of education had significantly lower mean BMIs. Compared to men from the METHODS Study population 2
1
' C E M Oldenburg', N.U. Cotten-Oldenburg , F. Rasmussen 1 Department of Family Practice and Community Health, University of Minnesota, Minneapolis, USA
2 AIDS and STD Prevention Services Section, Minnesota Department of Hearth, Minneapolis, USA 3 Division of Epidemiology, Institute of Environmental Medidne, Karolinska Instftutet, Stockholm, Sweden Correspond tnce: Finn Rasmussen, MD, MPH, PhD, Division of Epidemiology, Karolinska University Hospital, S-171 76 Stockholm, Sweden, tel. +46 8 S1776592, fax +46 8 51776529, e-mail: fjnn.ra3mussen4imm.kl.se
All male military conscripts for 1991-1994, born in Sweden between 1973 and 1975 to mothers whose own nationality was known, were eligible for the study. Between 1973 and 1975,165,005 males were born alive. Of these individuals 4,758 (2.8%) died within the first 18 years of age. Data on BMI from the military induction examination and on the mothers' nationality were available for 140,766 (87.8%) of the remaining 160,247 young men who comprised the study population.
Ethnic differences in being overweight and obesity Information sources and statistical analysis used to calculate adjusted odds ratios with 95% confidThe mothers' and conscripts' unique personal identience intervals. fication numbers were used to create a record linkage between three different registers. The Swedish Medical RESULTS Birth Register was used to collect data on year of birth and The mean age of the study population was 18.2 years child's sex. Statistics Sweden's Register of the Total (standard deviation 0.37 years). Of the 140,766 Swedish Population was used to obtain data on each mothers' male military conscripts born in 1973-1975, 7,624 nationality when her son was 18 years of age. Finally, the (5.42%) were in immigrant country groups according to National Register of Military Induction Examinations dieir mothers' nationality. The Finland country group supplied data on height, weight, level of education and had the highest percent of all with 3,880 conscripts of geographical region at 18 years of age. immigrant background (50.9%) followed by Eastern The data on the mothers' nationality were used to classify European countries (20.1%), other Nordic countries all the military conscripts into nine country groups deter(12.8%), other Western European countries and North mined according to population characteristics such as America (11.0%), the Middle East and North Africa ethnic background and/or geographic location: i) Swe(2.4%), Asia and the Pacific Islands (13%), Central and den; ii) Finland; iii) other Nordic countries excluding Soudi America (1.2%) and Sub-Saharan Africa (0.3%). Sweden and Finland; iv) Western Europe and North Of all 140,766 conscripts, 113,273 (80.5%) had a BMI in America including Australia, New Zealand and Israel, the normal range, while 15,046 (10.7%) were overweight and excluding all the Nordic countries; v) Eastern Europe, and 3,458 (2.4%) were obese. In bivariate analyses the vi) Sub-Saharan Africa; vii) Middle East and North risks of being overweight and obesity were consistently Africa; viii) Southeast Asia and the Pacific Islands; and higher among the conscripts whose mothers were ix) Central and South America. Dichotomous variables immigrants from Finland and former Eastern Europe were created for these country groups with Sweden as the (table I ) . reference group. The increased risks of being overweight and obesity for Potential confounding factors are age, level of education these two country groups persisted after adjustment for and geographical region. The geographical region varigeographical region and education by logistic regression able was divided into three categories (rural areas, meanalyses (table 2). The results in table 2 also show that the dium/large cities, and metropolitan cities); and the level risk of being overweight was lower among conscripts with of education was divided into four categories (elementary, high education and those living in metropolitan cities gymnasium for two years, gymnasium for greater than two compared to conscripts with low education or living in years, and university education). rural areas. Among the Finland and Eastern Europe groups, military conscriptsraisedin rural areas (OR= 1.25 An overweight variable was used to compare the overand 95% CI: 1.20-1.31) and medium/large cities weight group (BMI of 25.00-29.99 kg/m2) to the normal (OR=1.13 and 95% CI: 1.08-1.18) were at higher risks weight group (BMI of 18.50—24-99 kg/m2) and an obesity for overweight when compared to those conscripts raised variable compared the obesity group (BMI ^30.00 kg/m2) in metropolitan cities. Similarly the conscripts raised in to the normal weight BMI group. Using logistic regression rural areas (OR=1.82, 95% CI: 1.65-2.01) and meprocedures, being overweight and obesity were modelled dium/large cities (OR=1.39, 95% CI: 1.26-1.53) were at separately as a function of the country groups, controlling increased risk of obesity compared to conscripts raised in for age, geographical region and level of education. The metropolitan cities. CATMOD procedure of die SAS program package was Table 1 Bivariate analyses of being overweight and obesity among 1991-1994 military conscripts born in Sweden, by their mothers' country group Normal weight BMI 18.50-24.99 kg/m2
n
Obesity"
Overweight*
BMI 25.00-29.99 kg/m2 n OR 95% CI
BMI ^30.00 kg/m2 n OR 95% CI
Sweden
107,400
14,000
Finland
2,958
542 109
1.41 1.08
1.28-1.54 0.88-1.32
138 30
1.56
131-1.85
1.29
0.90-1.87
115 237 2 24 10 7
1.34 1.57 0.90
1.09-1.64 1.36-1.80 0.21-3.91
0.86
0.53-1.40
1.47
1.11-1.94
1.24 1.01
0.81-1.92
17 51 0 1 2 2
Other Nordic countries Odier Western Europe and North America Eastern Europe Sub-Saharan Africa Middle East and North Africa Asia and Pacific Islands Central and South America
774 658 1,162
17 148 76 80
3,217
0.67
0.52-1.95 0.31-1.45
3: Overweight and obesity are compared to normal weight. Each country group 15 compared to the Sweden country group. BMI: body mass index; OR: odds ratio; 95% CI: 95% confidence interval
-
-
0.23 0.88
0.03-1.61 0.22-3.58
0.84
0.21-3.40
EUROPEAN JOURNAL OF PUBLIC HEALTH VOL. 9 1999 NO. 2 DISCUSSION The Finland and Eastern Europe country groups were 38 and 68% more likely to be overweight after controlling for age, geographical region and level of education. In terms of obesity, the Finland and Eastern Europe country groups were 51 and 72% more likely to be obese after controlling for the same variables. Among the Finland and Eastern Europe country groups, those conscripts raised in rural areas were 25% more likely to be overweight and 82% more likely to be obese than those raised in metropolitan cities. In a recent Swedish study, Rasmussen et al. 3 found a strong inverse association between being overweight in young men and their mothers' level of education. A 1993 study in Sweden of 13,136 males aged 16-84 years old also revealed an inverse relationship between level of education and being overweight. 2 In the present study, the lack of a consistent inverse relationship in the groups from Finland and former Eastern Europe with regard to education and being overweight or obesity might be explained by limitations of the education variable. In Sweden, die majority of male students are 15—19 years old in gymnasium, 18—20 years old in die military and start studying at university at 19-20 years of age. The mean age of the study population, 18.2 years, precluded many conscripts from completing their education prior to die military induction examination. In contrast to die study referred to above, 3 no information about the mothers' and/or fathers' level of education was available in die present study. Anodier limitation was die use of mothers' nationality to categorise the conscripts into country groups. Since some immigrant women will have become Swedish citizens, a more accurate variable would have been mothers' country of birth but this information was not available in the present data set. The use of die variable of modiers' nationality most likely inflated the number of conscripts in the Sweden country group and decreased die number of true immigrant children in the odier country groups. Table 2 Logistic regression analyses of being overweight and obesity among Finnish and Eastern European military conscripts born in Sweden 1990—1994 by their mothers' country group controlling for age, geographical region and educational level of the conscripts Overweight1 OR 95% CI Finland Eastern Europe Rural areas0 Medium/large citiesc Elementary school Gymnasium 2 years Gymnasium >2 years
138 1.68 1.25 1.13 1.14 1.07 0.68
1.26-1.52 1.46-1.94 1.20-1.31 1.08-1.18 1.02-1.29 1.02-1.12 0.64-0.71
Obesity1
OR 1.51 1.72 1.82 1.39 1.40
95% Cl 1.27-1.80 130-2.29 1.65-2.01 1.26-1.53 1.16-1.70
0.87 0.80-0.95 034 0.31-0.38
a: Overweight and obesity arc compared to normal weight. tu Finland and Eastern Europe are compared to die Sweden group. c: Rural areas and medium/large cities are compared to metropolitan cities. d: Elementary education, gymnasium 2 years and gymnasium >2 years are compared to university educauon. ORj odds ratio, 95% CI: 95% confidence interval
No data was provided on fadiers' nationality or country of birth. Despite the limitations stated above, diis study adds to the international literature on differences in being overweight and obesity among ethnic minority groups and edinic majority groups. The higher prevalence of being overweight and obesity among the groups from Finland and former Eastern Europe may be influenced by biological, behavioural and cultural differences among diese groups compared to die Sweden group. It is noteworthy that all young men in the present study were born in Sweden and most likely went to die same types of day care centres and schools during childhood as die sons of die Swedish modiers. A recent paper from the US speculated diat behavioural, cultural and biological factors, including diet, physical activity level and resting energy expenditure might partly explain the differences in obesity prevalence between African-American women and White women. 11 From this perspective it is possible that the sons of immigrants from Finland and former Eastern Europe differ from the sons of Swedish mothers with respect to diet and physical activity but further research is needed to shed light on die reasons for the observed edinic differences in being overweight and obesity.
1 Kuczmarski RJ, Flegal KM, Campbell SM. Johnson CL Increasing prevalence of overweight among US adults: the national health and nutrition examination surveys, 1960 to 1991. JAMA 1994,272:205-11. 2 Kuskowska-Wolk A, Bergstrom R. Trends in body mass index and prevalence of obesity in Swedish men 1980-89. J Epidemiol Commun Hlth 1993;47:103-8. 3 Rasmussen F, Johansson M, Hansen HA. Trends in overweight and obesity among 18-year-old males in Sweden between 1971 and 1995. Acta Paediatr 1999. In press. 4 Rasmussen F, Johansson M. The relation of weight length and Ponderal index at birth to body mass index and overweight among 18-year-old males in Sweden. Eur J Epidemiol 1998; 14:373-80. 5 Prentice AM, Jebb SA. Obesity in Britain: gluttony or sloth? BMJ 1995;311:437-9. 6 Jalkanen L Tuomilehto J, Nisslnen A, Puska P. Changes in body mass index in a Finnish population between 1972 and 1982. J Intern Med 1989;226:163-70. 7 Blockstra A, Kronhout D. Trends in obesity in young adults in The Netherlands from 1974 to 1986. Int J Obesity 1991;15:513-21. 8 Gallagher D, Visser M, Sepurveda D, Pierson RN, Harris T, Heymsfield SB. How useful is body mass index or comparison of body fatness across age, sex, and ethnic groups? Am J Epidemiol 1996;143:228-38. 9 Norgan NG. Population differences in body composition in relation to the body mass index Eur J Clin Nutr 1994;48(Suppl3):10S-27S. 10 Flegal KM, Harlan WR, Landis JR. Secular trends in body mass index and skin fold thickness with socio-economic factors in young adult men. Am J Clin Nutr 1988;48:544-51. 11 Forster GD, Wadden TD, Vogt RA. Resting energy expenditure in obese African American and Caucasian women. Obesity Res 1997;5:1-8.
Received 10 March 1998, accepted 6 November 1998
