New data for action. Data collection for KiGGS Wave 2 has been completed

The fieldwork of the second follow-up to the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) was completed in August 2017. KiGGS is part of the Robert Koch Institute's Federal Health Monitoring. The study consists of the KiGGS cross-sectional component (a nationally representative, periodic cross-sectional survey of children and adolescents aged between 0 and 17) and the KiGGS cohort (the follow-up into adulthood of participants who took part in the KiGGS baseline study). KiGGS collects data on health status, health-related behaviour, psychosocial risk and protective factors, health care and the living conditions of children and adolescents in Germany. The first interview and examination survey (the KiGGS baseline study; undertaken between 2003 and 2006; n=17,641; age range: 0-17) was carried out in a total of 167 sample points in Germany. Physical examinations, laboratory analyses of blood and urine samples and various physical tests were conducted with the participants and, in addition, all parents and participants aged 11 or above were interviewed. The first follow-up was conducted via telephone-based interviews (KiGGS Wave 1 2009-2012; n=11,992; age range: 6-24) and an additional sample was included (n=4,455; age range: 0-6). KiGGS Wave 2 (2014-2017) was conducted as an interview and examination survey and consisted of a new, nationwide, representative cross-sectional sample of 0- to 17-year-old children and adolescents in Germany, and the second KiGGS cohort follow-up. The completion of the cross-sectional component of KiGGS Wave 2 means that the health of children and adolescents in Germany can now be assessed using representative data gained from three study waves. Trends can therefore be analysed over a period stretching to over ten years now. As the data collected from participants of the KiGGS cohort can be individually linked across the various surveys, in-depth analyses can be conducted for a period ranging from childhood to young adulthood and developmental processes associated with physical and mental health and the associated risk and protective factors can be explored. As such, KiGGS Wave 2 expands the resources available to health reporting, as well as policy planning and research, with regard to assessing the health of children and adolescents in Germany.

Busch M, Du Y, Heidemann C, Knopf H, Kuhnert R, Lampert T, Mensink GBM, K. Neuhauser H, Schaffrath Rosario A, Scheidt-Nave C, Schienkiewitz A, Truthmann J, Kurth BM. Time Trends in Cardiometabolic Risk Factors in Adults

BACKGROUND

Data from three representative health examination surveys in Germany were analyzed to examine secular trends in the prevalence and magnitude of cardiometabolic risk factors.

METHODS

The target variables were the following cardiometabolic risk factors: lack of exercise, smoking, obesity, systolic blood pressure, total cholesterol, serum glucose, self-reported high blood pressure, hyperlipidemia, and diabetes, and the use of antihypertensive, cholesterol-lowering, and antidiabetic drugs. 9347 data sets from men and 10 068 from women were analyzed. The calculated means and prevalences were standardized to the age structure of the German population as of 31 December 2010 and compared across the three time periods of the surveys: 1990-1992, 1997-1999, and 2008-11.

RESULTS

Over the entire period of observation (1990-2011), the mean systolic blood pressure fell from 137 to 128 mmHg in men and from 132 to 120 mmHg in women; the mean serum glucose concentration fell from 5.6 to 5.3 mmol/L in men and from 5.4 to 5.0 mmol/l in women; and the mean total cholesterol level fell from 6.2 to 5.3 mmol/L in both sexes. In men, smoking and lack of exercise became less common. On the other hand, the prevalence of use of antidiabetic, cholesterol-lowering, and antihypertensive drugs rose over the same time period, as did that of self-reported diabetes. The first of the three surveys (1990-1992) revealed differences between persons residing in the former East and West Germany in most of the health variables studied; these differences became less marked over time, up to the last survey in 2008-2011.

CONCLUSION

The cardiometabolic risk profile of the German adult population as a whole improved over a period of 20 years. Further in-depth analyses are now planned.

Cytomegalovirus Seroprevalence Among Children and Adolescents in Germany: Data From the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), 2003-2006

CMV seroprevalence increases with age and is significantly associated with migration background, country of origin, and place of birth. We identified the birth order of siblings, breastfeeding, early day care attendance and living in East Germany as further risk factors.

Background. Congenital cytomegalovirus (CMV) infection can cause severe birth defects. The majority of children with congenital CMV are born to CMV-seropositive women; however, transmission from mother to fetus and resulting defects are more likely to occur when mothers experience seroconversion during pregnancy. The objective of this study was to provide a population-based estimate of CMV seropositivity and to identify factors that correlate with the detection of CMV-immunoglobulin (Ig)G antibodies.

Methods. Cytomegalovirus-specific IgG antibodies were determined by enzyme-linked immunosorbent assay in 13 876 serum samples from children and adolescents (aged 1–17 years). Cytomegalovirus seroprevalence was correlated with children's age, gender, migration background, country of origin, place of birth, socioeconomic status, breast feeding, daycare attendance, order and number of siblings, and residence in East versus West Germany.

Results. Age-adjusted seroprevalence was 27.4% (95% confidence interval, 25.8–29.0). Cytomegalovirus seroprevalence increased with age (21.5% at ages 1–2; 32.0% at ages 14–17). Cytomegalovirus seropositivity was significantly associated with migration background, country of origin and place of birth, and (among migrants only) with low socioeconomic status. Risk factors for CMV acquisition included the birth order of siblings, breastfeeding, early daycare attendance, and living in East Germany.

Conclusions. In Germany, CMV seroprevalence increases with age, irrespective of gender. These data highlight risk factors associated with seroprevalence and help to identify a target age for the application of a CMV vaccine.

Changes in diabetes care indicators: findings from German National Health Interview and Examination Surveys 1997-1999 and 2008-2011

OBJECTIVES

To investigate changes in type 2 diabetes care indicators over time in Germany.

METHODS

Adults aged 45-79 years with type 2 diabetes were identified from two national health examination surveys conducted in 1997-1999 (GNHIES98, n=333) and in 2008-2011 (DEGS1, n=526). We examined diabetes care indicators including treatment and preventive targets (glycemic control, blood pressure (BP), total cholesterol (TC), smoking, weight reduction, sports activity), self-management and care process measures (glucose self-monitoring, holding a diabetes passport, annual foot and eye examination; statin use), and the presence of diabetes-specific complications (diabetic nephropathy, retinopathy, neuropathy, diabetic foot, amputations) and comorbid cardiovascular disease (CVD) or chronic kidney disease (CKD). We calculated proportions of persons meeting these care indicators by survey and examined unadjusted and adjusted changes between surveys.

RESULTS

Significant improvement (GNHIES98 vs DEGS1) over time was observed for glycated hemoglobin (HbA1c) <7.0% (53 mmol/mol) (32.4% vs 65.4%), BP <130/80 mm Hg (32.0% vs 47.2%), TC <190 mg/dL (13.5% vs 41.9%), statin use (11.7% vs 35.9%), eye (51.1% vs 78.4%) and foot (48.0% vs 61.4%) examination within the past 12 months, diabetes-specific complications (29.7% vs 21.8%), and CVD (44.5% vs 37.1%). Blood glucose self-monitoring significantly increased (37.4% vs 62.8%), while holding a diabetes passport did not change. Current smoking did not change and obesity rose, although sports activity significantly increased over time. Proportions of adults achieving combination goals of HbA1c, BP, TC, and smoking cessation were low in both surveys in spite of significant improvement.

CONCLUSIONS

In Germany, the quality of diabetes care improved over time. There is much room for improvement, in particular regarding preventive goals and diabetes self-management.

Updated prevalence rates of overweight and obesity in 11- to 17-year-old adolescents in Germany. Results from the telephone-based KiGGS Wave 1 after correction for bias in self-reports

Background

The nationwide “German Health Interview and Examination Survey for Children and Adolescents” (KiGGS), conducted in 2003–2006, showed an increase in the prevalence rates of overweight and obesity compared to the early 1990s, indicating the need for regularly monitoring. Recently, a follow-up—KiGGS Wave 1 (2009–2012)—was carried out as a telephone-based survey, providing self-reported height and weight. Since self-reports lead to a bias in prevalence rates of weight status, a correction is needed. The aim of the present study is to obtain updated prevalence rates for overweight and obesity for 11- to 17-year olds living in Germany after correction for bias in self-reports.

Methods

In KiGGS Wave 1, self-reported height and weight were collected from 4948 adolescents during a telephone interview. Participants were also asked about their body perception. From a subsample of KiGGS Wave 1 participants, measurements for height and weight were collected in a physical examination. In order to correct prevalence rates derived from self-reports, weight status categories based on self-reported and measured height and weight were used to estimate a correction formula according to an established procedure under consideration of body perception. The correction procedure was applied and corrected rates were estimated.

Results

The corrected prevalence of overweight, including obesity, derived from KiGGS Wave 1, showed that the rate has not further increased compared to the KiGGS baseline survey (18.9 % vs. 18.8 % based on the German reference).

Conclusion

The rates of overweight still remain at a high level. The results of KiGGS Wave 1 emphasise the significance of this health issue and the need for prevention of overweight and obesity in children and adolescents.

Prevalence, trends, patterns and associations of analgesic use in Germany

Background

Despite the public health relevance of analgesic use, large-scale studies on this topic in Germany are lacking. This study describes the prevalence, trends, associations and patterns of use of prescription and over-the-counter (OTC) analgesics, focusing on five of the most common agents: aspirin, diclofenac, ibuprofen, naproxen and paracetamol.

Methods

Data from two representative population-based surveys: The German National Health Interview and Examination Survey 1998 (GNHIES98 n = 7099) and the German Health Interview and Examination Survey for Adults 2008–2011 (DEGS1 n = 7091) was investigated. Information on all medicines consumed in the previous 7 days was collected via computer-assisted personal interviews with adults aged 18–79 years. Associations between analgesic use and socio-demographic and health-behaviour factors were analysed using logistic regression models.

Results

Analgesic use has increased over the last decade from 19 to 21 %. This was exclusively due to the rise in OTC analgesic use from 10.0 to 12.2 %. Prescribed analgesic use remained constant (7.9 %). Findings from DEGS1 indicate that ibuprofen is the most commonly used analgesic followed by aspirin and paracetamol. OTC analgesic use is higher among women and smokers, but lower among older adults (65–79 years). Prescribed analgesics use is higher among women, older adults, smokers and obese adults with medium or high socio- economic status. Adults performing more than 2 h/week of physical exercise use fewer analgesics.

Discussion

Among the adult population of Germany, the prevalence of OTC analgesic use has significantly increased over the last decade. We found differences between adults consuming OTC and prescribed analgesics (or both) concerning their health behaviour and health conditions. International direct comparison between prevalence rates of analgesic use was limited due to varying availability of analgesics between countries and to methodological differences.

Conclusions

About one in five community dwelling adults aged 18–79 years in Germany use analgesics in a given week. Considering the potential harms of analgesic use, monitoring of prevalence, patterns and determinants of use at the population level are important steps to inform disease prevention and health promotion policies.

Association between hemoglobin A1c and all-cause mortality: results of the mortality follow-up of the German National Health Interview and Examination Survey 1998

OBJECTIVE

This study examined the association of HbA1c-defined glycemic status and continuous HbA1c with all-cause mortality.

RESEARCH DESIGN AND METHODS

The study population comprised 6,299 participants (aged 18-79 years) of the German National Health Interview and Examination Survey 1998, who were followed up for mortality for an average of 11.6 years. Glycemic status was defined as known diabetes (self-reported diagnosis or intake of antidiabetic medication) and based on HbA1c levels according to American Diabetes Association diagnostic criteria as undiagnosed diabetes (≥6.5% [≥48 mmol/mol]), prediabetes with very high (6.0-6.4% [42-46 mmol/mol]) or high diabetes risk (5.7-5.9% [39-41 mmol/mol]), and normoglycemia (<5.7% [<39 mmol/mol]). Associations between glycemic status and mortality were examined by Cox regression adjusting for age, sex, education, lifestyle factors, anthropometric measures, and history of chronic diseases (reference: normoglycemia). Spline models were fitted to investigate associations between continuous HbA1c and mortality among participants without known diabetes.

RESULTS

Excess mortality risk was observed for participants with known diabetes (hazard ratio 1.41 [95% CI 1.08-1.84]) and undiagnosed diabetes (1.63 [1.23-2.17]) but not for those with high (1.02 [0.80-1.30]) or very high diabetes risk (0.87 [0.67-1.13]). Spline models revealed a U-shaped association, with lowest risk at HbA1c levels 5.4-5.6% (36-38 mmol/mol) and a significantly increased risk at ≤5.0% (≤31 mmol/mol) and ≥6.4% (≥46 mmol/mol).

CONCLUSIONS

Unlike known and undiagnosed diabetes, HbA1c levels in the prediabetic range were not associated with an increased mortality risk. The observed U-shaped relationship adds to existing evidence that not only high but also low HbA1c levels might be associated with all-cause mortality.

Development and validation of correction formulas for self-reported height and weight to estimate BMI in adolescents. Results from the KiGGS study

OBJECTIVE

The use of reported instead of measured height and weight induces a bias in prevalence rates for overweight and obesity. Therefore, correction formulas are necessary.

METHODS

Self-reported and measured height and weight were available from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) baseline study (2003-2006) from 3,468 adolescents aged 11-17 years. With regression analyses, correction formulas for height and weight were developed. Cross-validation was conducted in order to validate and compare the formulas. Corrected BMI was calculated, and corrected prevalence rates were estimated. Sensitivity, specificity, and predictive values for overweight and obesity were calculated.

RESULTS

Through the correction procedure, the mean differences between reported and measured height and weight become remarkably smaller and thus the estimated prevalence rates more accurate. The corrected proportions for overweight and obesity are less under-reported, while the corrected proportions for underweight are less over-reported. Sensitivity for overweight and obesity increased after correction. Specificity remained high.

CONCLUSION

The validation process showed that the correction formulas are an appropriate tool to correct self-reports on an individual level in order to estimate corrected prevalence rates of overweight and obesity in adolescents for studies which have collected self-reports only.

Abdominal obesity in German adolescents defined by waist-to-height ratio and its association to elevated blood pressure: the KiGGS study

OBJECTIVE

The aim of this study was to compare the fixed 0.5 cut-off and the age- and sex-specific 90th percentile (P90) for waist-to-height ratio (WHtR) in German adolescents with respect to the prevalence of abdominal obesity and to compare the screening ability of WHtR and BMI to identify hypertensive blood pressure (BP) values.

METHODS

Between 2003 and 2006, the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) was carried out including 3,492 boys and 3,321 girls aged 11-17 years. Abdominal obesity was assessed by two WHtR cut-points (P90; 0.5). Hypertensive BP was defined as BP exceeding age-, sex- and height-specific 95th percentiles or the adult threshold for hypertension (140/90 mm Hg).

RESULTS

Agreement between the WHtR cut-offs was very good (Kappa 0.89 for boys; 0.81 for girls), and the prevalence of abdominal obesity was slightly higher using P90 (boys 12.0%; girls 11.3%) compared to 0.5 (boys 10.7%; girls 8.0%). WHtR and BMI-for-age had equivalent ability to discriminate hypertensive BP (ROC-AUC < 0.7; sensitivity of the 0.5 cut-off for detecting hypertensive BP < 30%).

CONCLUSION

The fixed 0.5 WHtR cut-off can be used in German adolescents to characterize abdominal obesity. However, WHtR is not suitable as a screening tool for hypertensive BP in adolescents.

Attributable risks for childhood overweight: evidence for limited effectiveness of prevention

OBJECTIVE

Calculation of attributable risks (ARs) of childhood overweight to estimate effectiveness of prevention strategies.

METHODS

We used pooled data of 4 population-based German studies including 34240 children and adolescents aged 3 to 18 years to calculate the impact of familial, social, "early life", and lifestyle factors on overweight. ARs (joint for all determinants as well as partial risks) were calculated.

RESULTS

The prevalence of childhood overweight was 13.4%. Successfully tackling all determinants can reduce overweight by 77.7% (ie, from 13.4% to 3.0%; = joint AR) with partial effects of treating parental overweight (42.5%); improving social status (14.3%); reducing media time to <1 hour per day (11.4%); and not smoking during pregnancy, low weight gain during pregnancy, and breastfeeding (together 9.5%), respectively. Improving all preventable risk factors (ie, early life factors and lifestyle) the effect is 9.2%. Media time has the strongest effect.

CONCLUSIONS

The determinants identified explained 78% of the prevalence of overweight. Taking into account the partial ARs, the effectiveness of lifestyle interventions to prevent overweight in children is limited. Our data argue in favor of interventions aimed at families and social environments, with a major focus on promoting a lower screen time and computer use in children.

German health interview and examination survey for adults (DEGS) - design, objectives and implementation of the first data collection wave

BACKGROUND

The German Health Interview and Examination Survey for Adults (DEGS) is part of the recently established national health monitoring conducted by the Robert Koch Institute. DEGS combines a nationally representative periodic health survey and a longitudinal study based on follow-up of survey participants. Funding is provided by the German Ministry of Health and supplemented for specific research topics from other sources.

METHODS/DESIGN

The first DEGS wave of data collection (DEGS1) extended from November 2008 to December 2011. Overall, 8152 men and women participated. Of these, 3959 persons already participated in the German National Health Interview and Examination Survey 1998 (GNHIES98) at which time they were 18-79 years of age. Another 4193 persons 18-79 years of age were recruited for DEGS1 in 2008-2011 based on two-stage stratified random sampling from local population registries. Health data and context variables were collected using standardized computer assisted personal interviews, self-administered questionnaires, and standardized measurements and tests. In order to keep survey results representative for the population aged 18-79 years, results will be weighted by survey-specific weighting factors considering sampling and drop-out probabilities as well as deviations between the design-weighted net sample and German population statistics 2010.

DISCUSSION

DEGS aims to establish a nationally representative data base on health of adults in Germany. This health data platform will be used for continuous health reporting and health care research. The results will help to support health policy planning and evaluation. Repeated cross-sectional surveys will permit analyses of time trends in morbidity, functional capacity levels, disability, and health risks and resources. Follow-up of study participants will provide the opportunity to study trajectories of health and disability. A special focus lies on chronic diseases including asthma, allergies, cardiovascular conditions, diabetes mellitus, and musculoskeletal diseases. Other core topics include vaccine-preventable diseases and immunization status, nutritional deficiencies, health in older age, and the association between health-related behavior and mental health.

Comparison of BMI derived from parent-reported height and weight with measured values: results from the German KiGGS study

The use of parent-reported height and weight is a cost-efficient instrument to assess the prevalence of children's weight status in large-scale surveys. This study aimed to examine the accuracy of BMI derived from parent-reported height and weight and to identify potential predictors of the validity of BMI derived from parent-reported data. A subsample of children aged 2-17 years (n = 9,187) was taken from the 2003-2006 cross-sectional German KiGGS study. Parent-reported and measured height and weight were collected and BMI was calculated. Besides descriptive analysis, linear regression models with BMI difference and logistic regression models with weight status misclassification as dependent variables were calculated. Height differences varied by gender and were generally small. Weight and BMI were under-reported in all age groups, the under-reporting getting stronger with increasing age. Overall, the proportion for overweight and obesity based on parental and measured reports differed slightly. In the youngest age group, the proportion of overweight children was overestimated, while it was underestimated for older children and adolescents. Main predictors of the difference between parent reported and measured values were age, gender, weight status and parents' perception of the child's weight. In summary, the exclusive use of uncorrected parental reports for assessment of prevalence rates of weight status is not recommended.

Validity and predictors of BMI derived from self-reported height and weight among 11- to 17-year-old German adolescents from the KiGGS study

Background

For practical and financial reasons, self-reported instead of measured height and weight are often used. The aim of this study is to evaluate the validity of self-reports and to identify potential predictors of the validity of body mass index (BMI) derived from self-reported height and weight.

Findings

Self-reported and measured data were collected from a sub-sample (3,468 adolescents aged 11-17) from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS). BMI was calculated from both reported and measured values, and these were compared in descriptive analyses. Linear regression models with BMI difference (self-reported minus measured) and logistic regression models with weight status misclassifications as dependent variables were calculated.

Height was overestimated by 14- to 17-year-olds. Overall, boys and girls under-reported their weight. On average, BMI values calculated from self-reports were lower than those calculated from measured values. This underestimation of BMI led to a bias in the prevalence rates of under- and overweight which was stronger in girls than in boys. Based on self-reports, the prevalence was 9.7% for underweight and 15.1% for overweight. However, according to measured data the corresponding rates were 7.5% and 17.7%, respectively. Linear regression for BMI difference showed significant differences according to measured weight status: BMI was overestimated by underweight adolescents and underestimated by overweight adolescents. When weight status was excluded from the model, body perception was statistically significant: Adolescents who regarded themselves as 'too fat' underestimated their BMI to a greater extent. Symptoms of a potential eating disorder, sexual maturation, socio-economic status (SES), school type, migration background and parental overweight showed no association with the BMI difference, but parental overweight was a consistent predictor of the misclassification of weight status defined by self-reports.

Conclusions

The present findings demonstrate that the observed discrepancy between self-reported and measured height and weight leads to inaccurate estimates of the prevalence of under- and overweight when based on self-reports. The collection of body perception data and parents' height and weight is therefore recommended in addition to self-reports. Use of a correction formula seems reasonable in order to correct for differences between self-reported and measured data.

Indicators of overweight and cardiovascular disease risk factors among 11- to 17-year-old boys and girls in Germany

OBJECTIVE

We analyzed the magnitude of the association between cardiovascular disease (CVD) risk factors and various measures of overweight among adolescents, to determine which indicator of overweight is most relevant for risk assessment.

METHODS

5,546 boys and girls aged 11-17 years participating in the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) were studied. Overweight was assumed when different anthropometric variables exceeded age- and sex-specific 90th percentiles. Blood pressure was measured and blood samples were analyzed for serum total cholesterol, lipoproteins, high-sensitivity C-reactive protein, and glycosylated hemoglobin (HbA1c).

RESULTS

In both sexes, overweight was significantly associated with adverse levels of CVD risk factors, except HbA1c. These associations were most pronounced for overweight as defined by waist circumference (WC), waist-to-height ratio (WHtR), or BMI. Between 11% and 37% of the overweight children exceeded the defined cut-offs for individual CVD risk factors, with age- and puberty-adjusted significant odds ratios (95% confidence interval (CI)) in comparison to normal-weight age mates ranging from 1.7 (1.0-3.0) to 6.1 (4.5-8.2).

CONCLUSIONS

The findings of this population-based survey suggest that, among adolescents, WC, WHtR, and BMI are easily applicable measures of overweight that appear to be relevant for CVD risk assessment.

German head circumference references for infants, children and adolescents in comparison with currently used national and international references

AIM

To present valid head circumference (HC) percentiles from early infancy to 18 years and to compare them with percentiles currently used in Germany by Prader, as well as to international WHO and CDC references.

METHODS

Nationally representative sample of 17,158 children and adolescents aged 0.25-17.98 years (KiGGS study 2003-2006) with standardized HC measurement. HC references were created using Cole's LMS method.

RESULTS

The median growth of HC is largest in the first year of life. Adult HC is reached at age 16 years in girls, while in boys, HC growth continues through age 17 years and adult HC have to be derived from future KiGGS follow-up examinations. KiGGS percentiles are quite similar from early infancy to early school age compared to older Prader references, but higher thereafter (maximum difference of median HC: girls 1.4 cm, boys 0.9 cm). KiGGS percentiles are also higher than WHO and CDC percentiles over most of the compared age range, but differences are less pronounced compared to Prader.

CONCLUSION

The KiGGS HC references presented here for boys and girls aged 4 months through 17 years are more valid than currently used German references. Because of the similarity of KiGGS and the currently used reference by Prader in early infancy, the currently used Prader reference for 0-4 months could complement KiGGS to cover the entire age range from birth to the end of adolescence.

Blood pressure percentiles by age and height from nonoverweight children and adolescents in Germany

OBJECTIVES

To present oscillometric blood pressure (BP) references from German nonoverweight children and compare them with US references.

METHODS

From children and adolescents, aged 3 to 17 years, from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS 2003-2006), we obtained standardized BP measurements by using an oscillometric device validated in children. Gender-specific systolic (SBP) and diastolic (DBP) BP percentiles, which simultaneously accounted for age and height by use of advanced statistical methods, were derived from nonoverweight children to avoid overweight prevalence in the reference population influencing BP references.

RESULTS

The age- and gender-specific 95th percentiles from nonoverweight children (n = 12 199) were lower by up to 3 mm Hg for SBP and up to 2 mm Hg for DBP compared with the total sample (N = 14 349). KiGGS percentiles from nonoverweight children accounting simultaneously for age and height were mostly lower than in the US reference sample but higher for SBP in boys aged 14 years or older. At median height, the age-specific differences in 95th percentiles of SBP ranged from -4 to 4 mm Hg in boys and -2 to 1 mm Hg in girls and, for DBP, from -6 to 2 mm Hg in boys and -5 to 2 mm Hg in girls.

CONCLUSIONS

Compared with current US references, the proposed German BP reference values are not influenced by the prevalence of overweight children in the reference population, they are based on a validated oscillometric device, and they take advantage of improved statistical methods.

Is low birth weight in the causal pathway of the association between maternal smoking in pregnancy and higher BMI in the offspring?

A number of cross-sectional and prospective studies suggested a priming effect of maternal smoking in pregnancy on offspring's obesity. It has been hypothesized that this association might be explained by low birth weight and subsequent catch-up growth in the causal pathway. We therefore examined the role of birth weight in children exposed versus not exposed to cigarette smoking in utero on later body mass index (BMI). Using data of 12,383 children and adolescents (3-17 years of age) recorded in a German population-based survey (KiGGS), we assessed mean body mass index standard deviation scores (BMI-SDS) in different birth weight SDS categories, stratified for children with smoking and non-smoking mothers. We calculated spline regression models with BMI-SDS as outcome variable, cubic splines of birth weight SDS, and potential confounding factors. Children whose mothers had been smoking during pregnancy had lower birth weight SDS and higher BMI-SDS at interview compared to children of non-smoking mothers. However, we observed a linear association between birth weight SDS and BMI-SDS in crude analyses for both groups. Similarly, almost linear effects were observed in adjusted spline regression analyses, except for children with very low birth weight. The respective 95% confidence bands did not preclude a linear effect for the whole birth weight SDS distribution. Our findings suggest that low birth weight is unlikely to be the main cause for the association between intrauterine nicotine exposure and higher BMI in later life. Alternative mechanisms, such as alterations in the noradrenergic system or increased food efficiency, have to be considered.

Risk factors for obesity: further evidence for stronger effects on overweight children and adolescents compared to normal-weight subjects

BACKGROUND

We recently showed that in preschoolers risk factors for overweight show stronger associations with BMI in children with high BMI values. However, it is unclear whether these findings might also pertain to adolescents.

METHODS

We extracted data on 3-10 year-old (n = 7,237) and 11-17 year-old (n = 5,986) children from a representative cross-sectional German health survey (KiGGS) conducted between 2003 and 2006 and calculated quantile regression models for each age group. We used z-scores of children's body mass index (BMI) as outcome variable and maternal BMI, maternal smoking in pregnancy, low parental socioeconomic status, exclusive formula-feeding and high TV viewing time as explanatory variables.

RESULTS

In both age groups, the estimated effects of all risk factors except formula-feeding on BMI z-score were greatest for children with the highest BMI z-score. The median BMI z-score of 11-17 year-old children with high TV viewing time, for example, was 0.11 [95% CI: 0.03, 0.19] units higher than the median BMI z-score of teenage children with low TV viewing time. This risk factor was associated with an average difference of 0.18 [0.06, 0.30] units at the 90(th) percentile of BMI z-score and of 0.20 [0.07, 0.33] units at the 97(th) percentile.

CONCLUSIONS

We confirmed that risk factors for childhood overweight are associated with greater shifts in the upper parts of the children's BMI distribution than in the middle and lower parts. These findings pertain also to teenagers and might possibly help to explain the secular shift in the upper BMI percentiles in children and adolescents.

Nationally representative waist circumference percentiles in German adolescents aged 11.0-18.0 years

OBJECTIVE

The aim of this study was to develop age- and sex-specific percentile curves for waist circumference (WC) in German adolescents.

METHODS

A cross-sectional population-based study (German Health Interview and Examination Survey for Children and Adolescents [KiGGS]) was carried out in a large nationally representative sample of 3 345 males and 3 221 females aged 11.0 to 18.0 years from May 2003 to May 2006. Smoothed percentile curves of WC were derived by the LMS method.

RESULTS

Girls had lower WC values than boys at any age and percentile. WC increased with age in both boys and girls. The curves show a fairly linear pattern for males, but for females they begin to level off after the age of 13 years.

CONCLUSIONS

The presented WC percentile curves are based on a representative sample of adolescents living in Germany and standardized measurements. We propose their use for clinical practice to monitor abdominal obesity in adolescents, although there is a need for future studies correlating cut-offs with health outcomes. The German curves could contribute to the feasibility of combining representative data from several countries to establish an international reference for WC.

Sleep duration and obesity in children: is the association dependent on age and choice of the outcome parameter?

STUDY OBJECTIVES

To assess the association between sleep duration in children and different markers of body fat by age and weight status.

DESIGN

Nation-wide health survey. Measurement of BMI and body fat percentage (KFA) calculated from weight, height, skin fold thickness, age, and sex. Sleep duration and potential confounding variables were assessed in a parent questionnaire.

SETTING

N/A.

PARTICIPANTS

7767 German resident children from 3 to 10 years of age.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Prolongation of sleep duration from the lowest to the highest percentile accounted for a similar mean decrease founding variables and did not show a systematic age dependency. The greatest effects of sleep duration were seen for the upper tails of the BMI and KFA distributions, which were about four as high as the lower tails.

CONCLUSIONS

The association between sleep duration and weight status is of similar size through ages 3 to 10 years. The sleep-associated changes in BMI are likely to be a consequence of higher body fat and primarily affect children whose BMI or KFA is already elevated. These findings favor hormonal pathways nurturing adipose tissue playing a key role in the underlying physiological mechanisms.

Potential determinants of obesity among children and adolescents in Germany: results from the cross-sectional KiGGS Study

BACKGROUND

Obesity among children and adolescents is a growing public health problem. The aim of the present paper is to identify potential determinants of obesity and risk groups among 3- to 17-year old children and adolescents to provide a basis for effective prevention strategies.

METHODS

Data were collected in the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), a nationally representative and comprehensive data set on health behaviour and health status of German children and adolescents. Body height and weight were measured and body mass index (BMI) was classified according to IOTF cut-off points. Statistical analyses were conducted on 13,450 non-underweight children and adolescents aged 3 to 17 years. The association between overweight, obesity and several potential determinants was analysed for this group as well as for three socio-economic status (SES) groups. A multiple logistic regression model with obesity as the dependent variable was also calculated.

RESULTS

The strongest association with obesity was observed for parental overweight and for low SES. Furthermore, a positive association with both overweight (including obesity) and obesity was seen for maternal smoking during pregnancy, high weight gain during pregnancy (only for mothers of normal weight), high birth weight, and high media consumption. In addition, high intakes of meat and sausages, total beverages, water and tea, total food and beverages, as well as energy-providing food and beverages were significantly associated with overweight as well as with obesity. Long sleep time was negatively associated with obesity among 3- to 10-year olds. Determinants of obesity occurred more often among children and adolescents with low SES.

CONCLUSION

Parental overweight and a low SES are major potential determinants of obesity. Families with these characteristics should be focused on in obesity prevention.