Changes in shape and location of BMI distributions of Swedish children

Trends in childhood body mass index between 1936 and 2011 showed that underweight remained more common than obesity among 398 970 Danish school children

AIM

To examine trends in all body mass index (BMI) groups in children from 1936 to 2011.

METHODS

We included 197 694 girls and 201 276 boys from the Copenhagen School Health Records Register, born between 1930 and 1996, with longitudinal weight and height measurements (6-14 years). Using International Obesity Task Force criteria, BMI was classified as underweight, normal-weight, overweight and obesity. Sex- and age-specific prevalences were calculated.

RESULTS

From the 1930s, the prevalence of underweight was stable until a small increase occurred from 1950 to 1970s, and thereafter it declined into the early 2000s. Using 7-year-olds as an example, underweight changed from 10% to 7% in girls and from 9% to 6% in boys during the study period. The prevalence of overweight plateaued from 1950 to 1970s and then steeply increased from 1970s onwards and in 1990-2000s 15% girls and 11% boys at 7 years had overweight. The prevalence of obesity particularly increased from 1980s onwards and in 1990-2000s 5% girls and 4% boys at 7 years had obesity. These trends slightly differed by age.

CONCLUSION

Among Danish schoolchildren, the prevalence of underweight was greater than overweight until the 1980s and greater than obesity throughout the period. Thus, monitoring the prevalence of childhood underweight remains an important public health issue.

Changes in the age-specific body mass index distribution among urban children between 2002 and 2018 in Changsha, China

BACKGROUND

It had been reported that the increase in the prevalence of childhood overweight and obesity in several developed countries over the decade was largely a consequence of changes in the upper end of the body mass index (BMI) distribution. We speculated that the change in BMI distribution among Chinese children is different from that in developed countries. Therefore, we investigated the changes in the BMI distribution among urban children in Changsha, China.

METHODS

A secondary data analysis of the 2002 and 2018 Annual Survey on Students' Constitution and Health from Yuhua District, Changsha City, China was performed. The BMI distribution of children aged 6-15 years (n=72,061) was examined by calculating the BMI value at 5th, 50th, 85th, and 95th percentiles. Differences in the BMI value at the 5th, 50th, 85th, and 95th percentiles between 2002 and 2018 according to age and sex were calculated.

RESULTS

From 2002 to 2018, the standardized rate of underweight decreased from 6.9% to 3.4%, whereas that of obesity increased from 6.1% to 13.8%. The BMI of the population increased over the 16-year period. The greatest change between the years was seen in the 85th percentile, and moderate changes were seen in the 5th and 50th BMI percentiles. Also, the greatest changes in the BMI percentiles were evident at age 12-14 years.

CONCLUSIONS

The whole spectrum of BMI distribution among school-aged children shifted over the 16-year study period, although the increases were more marked in the upper than lower percentiles. Health professionals and health policymakers should develop strategies and interventions aimed at preventing adverse health effects caused by this change.

Socioeconomic inequalities in childhood-to-adulthood BMI tracking in three British birth cohorts

BACKGROUND

Body mass index (BMI) tracks from childhood-to-adulthood, but the extent to which this relationship varies across the distribution and according to socio-economic position (SEP) is unknown. We aimed to address this using data from three British cohort studies.

METHODS

We used data from: 1946 National Survey of Health and Development (NSHD, n = 2470); 1958 National Child Development Study (NCDS, n = 7747); 1970 British Cohort Study (BCS, n = 5323). BMI tracking between 11 and 42 years was estimated using quantile regression, with estimates reflecting correlation coefficients. SEP disparities in tracking were investigated using a derived SEP variable based on parental education reported in childhood. This SEP variable was then interacted with the 11-year BMI z-score.

RESULTS

In each cohort and sex, tracking was stronger at the upper end of the distribution of BMI at 42 years. For example, for men in the 1946 NSHD, the tracking estimate at the 10th quantile was 0.31 (0.20, 0.41), increasing to 0.71 (0.61, 0.82) at the 90th quantile. We observed no strong evidence of SEP inequalities in tracking in men in the 1946 and 1958 cohorts. In the 1970 cohort, however, we observed tentative evidence of stronger tracking in low SEP groups, particularly in women and at the higher end of the BMI distribution. For example, women in the 1970 cohort from low SEP backgrounds had tracking coefficients at the 50th, 70th, and 90th quantiles, which were 0.05 (-0.04; 0.15), 0.19 (0.06; 0.31), and 0.22 (0.02; 0.43) units higher, respectively, than children from high SEP groups.

CONCLUSION

Tracking was consistently stronger at the higher quantiles of the BMI distribution. We observed suggestive evidence for a pattern of greater BMI tracking in lower (compared to higher) SEP groups in the more recently born cohort, particularly in women and at the higher end of the BMI distribution.

Change in BMI Distribution over a 24-Year Period and Associated Socioeconomic Gradients: A Quantile Regression Analysis

OBJECTIVE

This study assessed the change in body mass index (BMI) distribution among 18- or 19-year-olds over 24 years. It also investigated parallel changes in the distribution of birth weight and in the association between birth weight and later risk of overweight and/or obesity. Parental educational variations in the trends and associations were explored.

METHODS

The study used data on 606,832 male military conscripts enlisted between 1985 and 2008. Quantile regression was used to assess the temporal change in BMI and birth weight distribution. The association between birth weight and overweight and/or obesity at age 18 or 19 years was quantified by using logistic regression.

RESULTS

Increases in BMI over time were found namely in the 90th, 95th, 97th, and 99th percentiles. Socioeconomic differences in this increase were documented in the 75th to 97th percentiles. The distribution of birth weight and the association between birth weight and the risk of overweight and/or obesity at age 18 or 19 years remained stable over time.

CONCLUSIONS

The difference in the increase in BMI between low and high percentiles indicates the limited role of mean BMI in reflecting population changes. The results suggest a need to focus on those with low socioeconomic position in the upper ends of the BMI distribution to combat increasing disparities in obesity-related outcomes.

Trends in Socioeconomic Inequalities in Body Mass Index, Underweight and Obesity among English Children, 2007-2008 to 2011-2012

Background

Socioeconomic inequalities in childhood obesity have been reported in most developed countries, with obesity more common in deprived groups. Whether inequalities are found in the prevalence of underweight, the rest of the body mass index (BMI) distribution, or have changed across time is not clear.

Methods and Findings

The sample comprised 5,027,128 children on entry (4 to 5 years old) and leaving (10 to 11 years) state primary (elementary) school who participated in the National Child Measurement Programme (England, United Kingdom). We used area-level deprivation (Indices of Multiple Deprivation at the lower super output area) as a measure of socioeconomic deprivation. From 2007–2008 to 2011–2012 inequalities in obesity between the most compared to least deprived group increased (from 7.21% to 8.30%; p<0.001), whereas inequalities in the prevalence of underweight (1.50% to 1.21%; p = 0.15) were stable during this period. There were no differences by age group or by sex, but a three-way interaction suggested inequalities in obesity had increased at a faster rate for 10 to 11 year old girls, than 4 to 5 year old boys, (2.03% vs 0.07%; p<0.001 for interaction). Investigating inequalities across the distribution of zBMI showed increases in mean zBMI (0.18 to 0.23, p<0.001) could be attributed to increases in inequalities between the 50^th and 75^th centiles of BMI. Using the 2011 to 2012 population attributable risk estimates, if inequalities were halved, 14.04% (95% CI 14.00% to 14.07%) of childhood obesity could be avoided.

Conclusions

Socioeconomic inequalities in childhood obesity and zBMI increased in England between 2007–2008 and 2011–2012. Inequalities in the prevalence of underweight did not change. Traditional methods of examining inequalities only at the clinical thresholds of overweight and obesity may have led the magnitude of inequalities in childhood BMI to be underestimated.

How Has the Age-Related Process of Overweight or Obesity Development Changed over Time? Co-ordinated Analyses of Individual Participant Data from Five United Kingdom Birth Cohorts

BACKGROUND

There is a paucity of information on secular trends in the age-related process by which people develop overweight or obesity. Utilizing longitudinal data in the United Kingdom birth cohort studies, we investigated shifts over the past nearly 70 years in the distribution of body mass index (BMI) and development of overweight or obesity across childhood and adulthood.

METHODS AND FINDINGS

The sample comprised 56,632 participants with 273,843 BMI observations in the 1946 Medical Research Council National Survey of Health and Development (NSHD; ages 2-64 years), 1958 National Child Development Study (NCDS; 7-50), 1970 British Cohort Study (BCS; 10-42), 1991 Avon Longitudinal Study of Parents and Children (ALSPAC; 7-18), or 2001 Millennium Cohort Study (MCS; 3-11). Growth references showed a secular trend toward positive skewing of the BMI distribution at younger ages. During childhood, the 50th centiles for all studies lay in the middle of the International Obesity Task Force normal weight range, but during adulthood, the age when a 50th centile first entered the overweight range (i.e., 25-29.9 kg/m2) decreased across NSHD, NCDS, and BCS from 41 to 33 to 30 years in males and 48 to 44 to 41 years in females. Trajectories of overweight or obesity showed that more recently born cohorts developed greater probabilities of overweight or obesity at younger ages. Overweight or obesity became more probable in NCDS than NSHD in early adulthood, but more probable in BCS than NCDS and NSHD in adolescence, for example. By age 10 years, the estimated probabilities of overweight or obesity in cohorts born after the 1980s were 2-3 times greater than those born before the 1980s (e.g., 0.229 [95% CI 0.219-0.240] in MCS males; 0.071 [0.065-0.078] in NSHD males). It was not possible to (1) model separate trajectories for overweight and obesity, because there were few obesity cases at young ages in the earliest-born cohorts, or (2) consider ethnic minority groups. The end date for analyses was August 2014.

CONCLUSIONS

Our results demonstrate how younger generations are likely to accumulate greater exposure to overweight or obesity throughout their lives and, thus, increased risk for chronic health conditions such as coronary heart disease and type 2 diabetes mellitus. In the absence of effective intervention, overweight and obesity will have severe public health consequences in decades to come.

Trends in group inequalities and interindividual inequalities in BMI in the United States, 1993-2012

BACKGROUND

Marked increases in mean body mass index (BMI) and prevalence of obesity and overweight in the United States are well known. However, whether these average increases were accompanied by changing dispersion (or SD) remains understudied.

OBJECTIVE

We investigated population-level changes in the BMI distribution over time to understand how changes in dispersion reflect between-group compared with within-group inequalities in weight gain in the United States.

DESIGN

Using data from the Behavioral Risk Factor Surveillance System survey (1993-2012), we analyzed associations between mean, SD, and median BMI and BMI at the 5th and 95th percentiles for 3,050,992 non-Hispanic white, non-Hispanic black, and Hispanic men and women aged 25-64 y.

RESULTS

Overall, an increase of 1.0 in mean BMI (in kg/m²) was associated with an increase of 0.70 (95% CI: 0.67, 0.73) in the SD of BMI. A change of 1.0 in median BMI was associated with a change of 0.18 (95% CI: 0.14, 0.21) in the BMI value at the 5th percentile compared with a change of 2.94 (95% CI: 2.81, 3.07) at the 95th percentile. Quantile-quantile plots showed unequal changes in the BMI distribution, with pronounced changes at higher percentiles. Similar patterns were observed in subgroups stratified by sex, race-ethnicity, and education with non-Hispanic black women and women with less than a high school education having highest mean BMI, SD of BMI, and BMI values at the 5th and 95th percentiles.

CONCLUSIONS

Mean BMI and the percentage of overweight and obese individuals do not fully describe population changes in BMI. Increases in within-group inequality in BMI represent an underrecognized characteristic of population-level weight gain. Crucially, similar increases in dispersion within groups suggest that growing inequalities in BMI at the population level are not driven by these socioeconomic and demographic factors. Future research should focus on understanding factors driving inequalities in weight gain between individuals.

WHO European Childhood Obesity Surveillance Initiative 2008: weight, height and body mass index in 6-9-year-old children

What is already known about this subject Overweight and obesity prevalence estimates among children based on International Obesity Task Force definitions are substantially lower than estimates based on World Health Organization definitions. Presence of a north-south gradient with the highest level of overweight found in southern European countries. Intercountry comparisons of overweight and obesity in primary-school children in Europe based on measured data lack a similar data collection protocol. What this study adds Unique dataset on overweight and obesity based on measured weights and heights in 6-9-year-old children from 12 European countries using a harmonized surveillance methodology. Because of the use of a consistent data collection protocol, it is possible to perform valid multiple comparisons between countries. It demonstrates wide variations in overweight and obesity prevalence estimates among primary-school children between European countries and regions.

BACKGROUND

Nutritional surveillance in school-age children, using measured weight and height, is not common in the European Region of the World Health Organization (WHO). The WHO Regional Office for Europe has therefore initiated the WHO European Childhood Obesity Surveillance Initiative.

OBJECTIVE

To present the anthropometric results of data collected in 2007/2008 and to investigate whether there exist differences across countries and between the sexes.

METHODS

Weight and height were measured in 6-9-year-old children in 12 countries. Prevalence of overweight, obesity, stunting, thinness and underweight as well as mean Z-scores of anthropometric indices of height, weight and body mass index were calculated.

RESULTS

A total of 168 832 children were included in the analyses and a school participation rate of more than 95% was obtained in 8 out of 12 countries. Stunting, underweight and thinness were rarely prevalent. However, 19.3-49.0% of boys and 18.4-42.5% of girls were overweight (including obesity and based on the 2007 WHO growth reference).The prevalence of obesity ranged from 6.0 to 26.6% among boys and from 4.6 to 17.3% among girls. Multi-country comparisons suggest the presence of a north-south gradient with the highest level of overweight found in southern European countries.

CONCLUSIONS

Overweight among 6-9-year-old children is a serious public health concern and its variation across the European Region highly depends on the country. Comparable monitoring of child growth is possible across Europe and should be emphasized in national policies and implemented as part of action plans.

Changes in adiposity indicators of Ho Chi Minh City adolescents in a 5-year prospective cohort study

OBJECTIVE

The aim of this study was to examine changes over 5 years in body mass index (BMI) and waist circumference (WC) of adolescents from Ho Chi Minh City by age, gender and household economic status.

METHODS

Anthropometry including height, weight and WC measurements of 759 secondary high school students were collected 1-year apart in a prospective cohort study, between 2004 and 2009. BMI was calculated and overweight/obesity was defined using International Obesity Task Force (IOTF) BMI cutoffs. Abdominal 'overweight' and 'obesity' were defined as WC >91st-97th and 98th centile, respectively. BMI z-scores were also created.

RESULTS

Over the 5-year period, the absolute changes in mean BMI and WC were statistically significant (P<0.001). Boys had higher BMI and WC values than girls (P<0.001). The prevalence of overweight and obesity defined by IOTF BMI cutoff values increased gradually from 12.5% and 1.7% in the first year to 16.7% and 5.1% in the last year. Using WC cutoff values, the prevalence of abdominal overweight and obesity increased from 12.9% and 1.8% to 18.5% and 6.6%, respectively. BMI z-score curves shifted towards the right-hand side of the distribution (that is, towards overweight and obesity).

CONCLUSION

Overweight and obesity, as measured by BMI or WC, continued to increase among adolescents of Ho Chi Minh City over the 5-year period.

Contributions of incidence and persistence to the prevalence of childhood obesity during the emerging epidemic in Denmark

Background

Prevalence of obesity is the result of preceding incidence of newly developed obesity and persistence of obesity. We investigated whether increasing incidence and/or persistence during childhood drove the prevalence of childhood obesity during the emerging epidemic.

Methods

Height and weight were measured at ages 7 and 13 years in 192,992 Danish school children born 1930–1969. Trends in the incidence (proportion obese at 13 years among those not obese at 7 years) and persistence (proportion obese at 13 years among those obese at 7 years) across birth cohort periods (1930–41 with low stable prevalence of obesity, 1942–51 with increasing prevalence, 1952–69 with the higher, but stable prevalence) were investigated. Logistic regression was used to examine the associations between BMI at 7 years as a continuous trait, allowing interactions with the birth cohorts, and occurrence of obesity at 13 years.

Results

The prevalence of obesity was similar at 7 and 13 years and increased across birth cohorts in boys from around 0.1% to 0.5% and in girls from around 0.3% to 0.7%. The incidence of obesity between ages 7 and 13 years increased from 0.15% to 0.35% in boys and from 0.20% to 0.44% in girls. The persistence increased from 28.6% to 41.4% in boys and from 16.4% to 31.0% in girls. Despite a decrease over time, the remission of obesity occurred in >60% of obese children in the last birth cohort. However, the odds ratios of obesity at age 13 years in relation to the full range of BMI at 7 years remained unchanged across the birth cohort periods.

Conclusions/Significance

The development of the obesity epidemic in children was due to an increase in both incidence and persistence of obesity. Contrary to prevailing expectations, a large, although declining, proportion of children obese at an early age underwent remission during childhood.

Prediction of obesity from infancy to adolescence

AIM

To examine the development of childhood obesity and to determine the earliest age when estimating body mass using only weight and height data is associated with a corresponding estimate at the age of 15.

METHODS

Subjects included are all children born in 1991 in Östergötland County, Sweden. Weight and height data collected during regular check-ups at well-child centres and school health care assessments up to 15 years of age were assembled from health records. Correlations between childhood estimates of body mass and the body mass index (BMI) at 15 years of age were computed pairwise. Correlations with r > 0.5 were defined as reliably strong.

RESULTS

Complete data were available for 3579 children (62%). Fewer girls (2.6%; C.I. 1.9-3.3) than boys (4.6%; C.I. 3.7-5.5) were obese at 15 years of age. Correlations with BMI at 15 years of age were strong (significantly higher than 0.5) from 5 years of age. Only 23% of girls and 8% of boys found to be obese at 5 years of age were of normal weight at the age of 15.

CONCLUSION

From 5 years of age, point estimates of body mass using only weight and height data are strongly associated with BMI at the age of 15. More data sources are needed to predict weight trajectories in younger children.

Toddlers get slimmer while adolescents get fatter--BMI distribution in five birth cohorts from four decades in Finland

AIM

To investigate the trends in the size of Finnish children in five birth cohorts from four decades.

METHODS

This is a retrospective longitudinal growth pattern study on children representing five birth cohorts: 1974, 1981, 1991, 1995 and 2001 from the city of Tampere and three rural municipalities. Growth data were collected from birth to 15 years of age, except in birth cohorts 1995 and 2001 until 12 and 5 years. Body mass index (BMI, kg/m²) was calculated. Pearson's chi-square test was used in analysis.

RESULTS

The 50th percentile of BMI at birth varied between the 1970's and 2000's (boys: p<0.001, girls: p=0.02), with increase seen in girls. The 50th BMI percentile remained unchanged in 6-month-aged boys, whereas in girls, it varied inconsistent (p=0.04). At 1 and 2 years of age, the 15th, 50th, 85th and 95th BMI percentiles decreased (p=0.26 to <0.001). The 50th BMI percentile remained fairly constant at 5 and 7 years of age. In 12- and 15-year-old boys, the 50th, 85th and 95th percentiles of BMI showed a marked increase (p=0.01 to <0.001). In 12-year-old girls, only the 85th BMI percentile increased (p=0.03).

CONCLUSIONS

During the last three decades, Finnish toddlers have become markedly slimmer. Concurrently, an opposite change has taken place in adolescent boys.

Change in prevalence of overweight and obesity in Finnish children - comparison between 1974 and 2001

OBJECTIVE

To analyse the possible changes in the prevalence of overweight and obesity comparing birth cohorts from four different decades in Finland.

DESIGN

A retrospective longitudinal growth study.

METHODS

The subjects representing five birth cohorts: 1974 (n = 1109), 1981 (n = 987), 1991 (n = 586), 1995 (n = 856) and 2001 (n = 766) in the city of Tampere and three rural municipalities in Finland. Data included five consecutive height and weight measurements from 2 to 15 years of age. Normal weight, overweight and obesity at the time points were classified by body mass index (BMI, kg/m(2) ) according to international age- and gender-specific BMI cut-off points. The chi-square test was used to analyse the differences in the between birth cohorts.

RESULTS

The combined prevalence of overweight and obesity decreased significantly in 2-year-old boys (p = 0.009) and girls (p = 0.002) from 1974 to 2001. Insignificant fluctuation was seen in 5- and 7-year-old children. Both the prevalence of obesity and the combined prevalence of overweight and obesity showed a significant increase in 12- (p = 0.031 and p < 0.001) and 15-year-old boys (p < 0.001 in both) from the 1970s to 2000s. In girls, the prevalence of obesity as well as the combined prevalence of overweight and obesity increased significantly in the age group of 12 years (p = 0.023), but not in that of 15 years.

CONCLUSIONS

During the last three decades, overweight and obesity have become clearly more prevalent in Finnish young adolescents. This trend has been more obvious in boys than in girls. At the same time, 2-year-old children have shown an opposite trend.

Growth in children with cerebral palsy during five years after selective dorsal rhizotomy: a practice-based study

BACKGROUND

Overweight is reported as a side effect of SDR. The aims were to study the development of weight, height and body mass index (BMI) during five years after SDR.

METHODS

This prospective, longitudinal and practice-based study included all 56 children with CP spastic diplegia undergoing SDR from the start in March 1993 to April 2003 in our hospital. The preoperative Gross Motor Function Classification System (GMFCS) levels were I-II in 17, III in 15, IV-V in 24 children. Median age at SDR was 4.3 years (range 2.4-7.4 years). Weight and height/recumbent length were measured. Swedish growth charts for typically developing children generated weight, height and BMI z-scores for age and gender.

RESULTS

The preoperative median z-scores were for height -1.92 and for body mass index (BMI) -0.22. Five years later, the median BMI z-score was increased by + 0.57 (p < 0.05). The occurrence of thinness (BMI < -2 SD) was decreased (n.s.) and obesity (BMI > + 2 SD) increased (p < 0.05). Baseline BMI and age at the start of follow-up influenced the BMI change during the five years (p < 0.001 and p < 0.05 respectively).The individual growth was highly variable, but a tendency towards increasing stunting with age was seen in severe gross motor dysfunction (GMFCS levels IV-V) and the opposite, a slight catch-up of height in children with walking ability (GMFCS levels I-III).

CONCLUSIONS

These are the first available subtype- and GMFCS-specific longitudinal growth data for children with CP spastic diplegia. Their growth potential according to these data should be regarded as a minimum, as some children were undernourished. It is unknown whether the spasticity reduction through SDR increased the weight gain velocity, or if the relative weight increase was part of the general "obesity epidemic".For some children the weight increase was highly desirable. In others, it resulted in overweight and obesity with risk of negative health effects. Weight and height should be monitored to enable early prevention of weight aberrations also causing problems with mobility, activity and participation.

Overweight and obesity in Norwegian children: prevalence and socio-demographic risk factors

AIM

The aim of this study was to estimate the prevalence of childhood overweight and obesity and to identify socio-demographic risk factors in Norwegian children.

METHODS

The body mass index of 6386 children aged 2-19 years was compared with the International Obesity Task Force (IOTF) cut-off values to estimate the prevalence of overweight including obesity (OWOB) and obesity (OB). The effect of socio-demographic factors on this prevalence was analysed using multiple ordinal logistic regression analysis in a subsample of 3793 children.

RESULTS

The overall prevalence of OWOB was 13.8% (13.2% in boys and 14.5% in girls, p = 0.146), but the prevalence was higher in primary school children aged 6-11 years (17%, p < 0.001). The risk of being OWOB or OB increased in children with fever siblings (p = 0.003) and with lower parental educational level (p = 0.001). There was no association with parental employment status, single-parent families or origin.

CONCLUSION

The prevalence of OWOB and OB in Norwegian primary school children is of concern. Socio-demographic factors have pronounced effects on the current prevalence of overweight and obesity in a cohort of Norwegian children. This knowledge could help to work out strategies to reduce the burden of overweight and obesity in children.

Childhood overweight and obesity prevalences levelling off in Stockholm but socioeconomic differences persist

BACKGROUND

Time trends in overweight, obesity and underweight among 10-year-old children were investigated between 1999 and 2003 with attention to gender and areas with different socioeconomic status (SES).

MATERIAL

The study was performed in Stockholm County, where schools within eight different SES areas were randomly sampled. In selected schools, data on height and weight were abstracted from school health records of 2416 ten-year-old boys and girls examined by school nurses in 1999 and 2183 examined in 2003.

RESULTS

Among boys, the prevalence of overweight was 21.6% in 1999 and 20.5% in 2003 (difference -1.1% (95% confidence interval (CI), -4.6; 2.4)) and for obesity 3.2 and 3.8% (difference 0.6% (95% CI, -0.9; 2.2)). Among girls overweight decreased from 22.1 to 19.2% (difference -2.9% (95% CI, -6.3; 0.6)) and obesity from 4.4 to 2.8% (difference -1.6% (95% CI, -3.1; 0.0)). There was a marginally significant difference in obesity trends in girls versus boys (P=0.051). The prevalence of underweight decreased nonsignificantly both in boys and in girls. Strong gradients, with more obesity and overweight in socioeconomically disadvantaged areas, were observed in both genders in 2003. Differences between SES areas were also seen in 1999 but were more pronounced in 2003. Among boys divergent trends in obesity were observed between 1999 and 2003, with evidence for increases in less affluent areas only.

CONCLUSION

This population-based study of 10-year-olds indicates that rates of obesity, overweight and underweight are stable in Stockholm County. However, obesity is more prevalent in relatively less advantaged SES.

Shift in the composition of obesity in young adult men in Sweden over a third of a century

OBJECTIVE

To assess whether the composition of the obese category (body mass index (BMI)> or =30) has changed during the last one-third of a century in young adult men.

DESIGN

Retrospective study of 1,580,913 men (18.3+/-0.4 years) representing 82% of the Swedish male population at military conscription age between 1969 and 2005. Measured height and weight were used to define moderate and morbid obesity as BMI 30-34.9 and > or =35, respectively. Data on socio-economic position (SEP), place of residence (urban, semi-urban and rural), age and test center were also collected.

RESULTS

From the period 1969-1974 to 2000-2005, the prevalence of moderate obesity almost quintupled (0.8-3.8%; P<0.0001), while morbid obesity increased 10-fold (0.1-1.3%; P<0.0001). The composition of the obese category changed from 12.9 to 25.1% morbidly obese during the same time, corresponding to an annual growth in the odds of 2.8% (CI(95%) 2.5-3.1%) per year within the obese category. Compared to 1969-1974, the odds ratios of obesity and morbid obesity, respectively, were 1.6 (1.6-1.7) and 1.9 (1.7-2.2) in 1980-1984, 2.8 (2.7-2.9) and 4.0 (3.5-4.5) in 1990-1994, and 6.0 (5.7-6.3) and 11.4 (10.1-12.9) in 2000-2005, after adjustment for SEP, urban/rural place of residence, age and test center. Extrapolation of the growth rate during the observation period resulted in an estimated 4% morbidly obese in 2020.

CONCLUSION

Morbid obesity increased faster than moderate obesity during the last 35 years. As the health risks and costs of obesity-related morbidity increase disproportionately in the morbidly obese, it is important to assess morbid obesity in prevalence studies, and distinguish the morbidly from the moderately obese in cost analyses.

Obesity in Swedish schoolchildren is increasing in both prevalence and severity

PURPOSE

To monitor and describe, on a national level, the development of body mass index (BMI), overweight, and obesity of schoolchildren in Sweden aged 7-18 years over a period of 8 years.

METHODS

Longitudinal and cross-sectional studies of two nationally representative cohorts. A representative sample of 3,749 individuals from a birth cohort of 109,663 individuals born in 1973, and another representative sample of 3,158 individuals from a birth cohort of 94,064 individuals born in 1981; 4.5% and 1.6% of those born in 1973 and 1981, respectively, were missing from the sample. Data regarding height and weight from school health records.

RESULTS

From age 7-18 year, a strong positive secular change in BMI is found at all ages, and the rate of overweight and obesity is increasing for both boys and girls. Furthermore, obesity is growing more severe.

CONCLUSIONS

Nationally representative longitudinal BMI data for two cohorts, in which nonresponse bias is minimized, permitted monitoring and revealed a nationwide strongly positive secular change in BMI in Sweden, over a period of 8 years for individuals aged 7-18 years.

Changes in BMI-distribution from 1966-69 to 1995-97 in adolescents. The Young-HUNT study, Norway

Background

The aim of this study was to explore changes in the BMI-distribution over time among Norwegian adolescents.

Methods

Height and weight were measured in standardised ways and BMI computed in 6774 adolescents 14–18 years who participated in the Young-HUNT study, the youth part of the Health-study of Nord-Trondelag County, Norway in 1995–97. The results were compared to data from 8378 adolescents, in the same age group and living in the same geographical region, collected by the National Health Screening Service in 1966–69.

Results

From 1966–69 to 1995–97 there was an increased dispersion and a two-sided change in the BMI-distribution. Mean BMI did not increase in girls aged 14–17, but increased significantly in 18 year old girls and in boys of all ages. In both sexes and all ages there was a significant increase in the upper percentiles, but also a trend towards a decrease in the lowest percentiles. Height and weight increased significantly in both sexes and all ages.

Conclusion

The increased dispersion of the BMI-distribution with a substantial increase in upper BMI-percentiles followed the same pattern seen in other European countries and the United States. The lack of increase in mean BMI among girls, and the decrease in the lowest percentiles has not been acknowledged in previous studies, and may call for attention.

Evaluation of BMI-based classification of adolescent overweight and obesity: choice of percentage body fat cutoffs exerts a large influence. The COMPASS study

OBJECTIVE

To determine the impact of commonly used body fat percentage (%BF) references when evaluating the sensitivity, specificity and misclassifications of body mass index (BMI) for obesity screening in adolescence.

SUBJECTS/METHODS

A community-based sample of 3334 adolescents aged 15.2+/-0.6 years was studied. Weight, height and %BF were measured. Sensitivity, specificity, predictive values and type and extent of misclassifications were calculated. True-positive subjects for overweight and obesity were defined by recently published paediatric %BF cutoffs, 85th and 95th percentiles from the present study population, and an older %BF reference.

RESULTS

Regardless of %BF reference used, specificities were high (>0.98 for obesity and >0.90 for overweight) in both sexes, with values for overweight consistently higher for girls (P<0.05). Sensitivities were much lower, with boys ranging from 0.52 to 0.74 for overweight, and 0.24 to 0.43 for obesity. Corresponding sensitivities for girls were 0.42-0.66 and 0.22-0.46. Large discrepancies were seen in total number of misclassifications, with published references resulting in twice as many misclassified for overweight (620, 514 vs 362) when compared to the cutoffs from the study population. For obesity, the difference was even greater (367 vs 133).

CONCLUSIONS

No matter which %BF reference used, specificity of BMI was high, and sensitivity low for both sexes. Population percentiles resulted in somewhat lower specificity but much higher sensitivity, and many more correctly classified compared to when cutoffs from the literature were used. The choice of %BF reference in evaluations of BMI-based classification systems has a large impact on the outcome. Sensitivity analyses are therefore warranted.

Overweight more prevalent among children than among adolescents

AIMS

To study if there is a change in paediatric overweight/obesity prevalence from 1982 to 2002 in a population with a high proportion of post-graduate education.

DESIGN

Two samples of children in Uppsala County, Sweden, were compared: children who were 4, 10 and 16 year old in 1982; or 4, 10 and 16 year old in 2002. Mean BMI (in the lowest 10%, middle 50% and highest 10%) and ISO-BMI ('age adjusted BMI') cut-off values were calculated in each age and gender group.

RESULTS

Using the mean BMI or ISO-BMI cut-off values, the BMI-distribution shifted from 1982 to 2002. More 4- and 10-year-old girls and boys were overweight/obese, although this shift was larger in girls. No shift was seen in the 16-year-olds, only the middle 50% group in the 16-year-old girls had a slight increase of their mean BMI. In the 2002 4-year-old, and both 10-year-old samples, a higher proportion of the girls were overweight/obese compared to the boys, but no difference was seen in the 16-year-old sample.

CONCLUSION

Young children, especially girls, have become much more overweight/obese during the past 20 years, despite a high proportion of post-graduate education in the population. The lack of major change in 16-year-olds may suggest a rather recent change in the children's environment/lifestyle.

Bias in height and weight reported by Swedish adolescents and relations to body dissatisfaction: the COMPASS study

OBJECTIVE

To assess the size of biases in self-reported height, weight in a large sample of adolescents with special attention to possible effects of body dissatisfaction and to assess how such biases may influence estimates of overweight and obesity.

DESIGN

Cross-sectional study.

SETTING

Unselected population from Southwestern parts of Stockholm County, Sweden.

SUBJECTS

Two-thousand seven hundred and twenty-six boys and girls, 15 years of age.

METHODS

Data were collected by a questionnaire answered by adolescents and a physical examination made by trained study nurses. A validated physical appearance scale and body silhouettes were embedded into the questionnaire.

RESULTS

Obese boys under-reported their weight (5.2 kg) (95% confidence intervals (CI) 3.7; 6.6) more than obese girls (3.8 kg) (95% CI 1.8; 5.8). Agreement between self-reported and measured body mass index (BMI)-categories (obese, overweight and non-overweight/obese) as estimated by weighted kappa was 0.77 (95% CI 0.72; 0.82) for girls and 0.74 (95% CI 0.70; 0.79) for boys. For obese girls and boys sensitivity of self-reports were 0.65 (95% CI 0.47; 0.79) and 0.52 (95% CI 0.38; 0.66). Boys with low scores on the physical appearance scale under-reported their weight and BMI more than those with high scores. Boys and girls who wished to be leaner under-reported their weight and BMI more than subjects who were satisfied with their body size (P<0.05).

CONCLUSION

Thirty-five percent of obese girls and 48% of obese boys would remain undetected from self-reported data. Boys and girls who were dissatisfied with their physical appearance or size under-reported their weight more than satisfied subjects.

Obesity in 4-year-old children more prevalent in girls and in municipalities with a low socioeconomic level

AIM

To provide updated prevalence data of BMI and obesity in 4-year-old Swedish children, also exploring socioeconomic differences.

SUBJECTS

A total of 4407 children born 1998-1999 (2231 boys and 2176 girls) in the county of Västerbotten, Sweden.

METHODS

Overweight and obesity was estimated using the International Obesity Task Force cutoff values (ISO BMI). Information about socioeconomic level of the municipalities was collected from a health survey of the adult population.

RESULTS

Of the boys, 16.7% were classified as overweight and 3.1% of these as obese. Corresponding figures for girls were 22.1% and 6%. [corrected] The P50 and P95 values for BMI were 16.2 and 18.8 for boys and 16.1 and 19.3 for girls, respectively. P50 was at the same level as in previous Swedish studies, while P95 was higher in this study. Obesity, in girls, was more prevalent in municipalities with a low socioeconomic level.

CONCLUSION

Overweight and obesity in pre-school children in Sweden is more prevalent in girls than in boys, and the prevalence is as high as in school age children. A low socioeconomic level of living area seems to be related to a higher prevalence of obesity. Increased preventive efforts, both on the individual and the societal level, must be undertaken to reduce future health risks in obese children.