Velocities of weight, height and fat mass gain during potentially critical periods of growth are decisive for adult body composition.

OBJECTIVES: To examine whether maximal velocities of weight, height and fat mass during potentially critical periods of growth were associated with body composition in young adulthood. SUBJECTS/METHODS: Analyses were performed on 277 female and 271 male participants of the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study with anthropometric measurements in young adulthood (18-25 years) as well as early life (0-2 years), mid-childhood (3-8 years) or puberty (9-15 years). Maximum growth velocities were calculated using the SuperImposition by Translation And Rotation (SITAR) routine or polynomial functions and related to adult fat mass index (FMI) and fat-free mass index (FFMI). RESULTS: In early life, faster weight gain was associated with a moderately higher FMI and FFMI in young adulthood in women only (Ptrend=0.01). In mid-childhood and puberty, weight and fat mass velocities were related to adult FMI and FFMI in both sexes (Ptrend⩽0.002): relative differences between the highest and lowest tertiles of these growth velocities ranged 33-69% for adult FMI and 6-12% for adult FFMI. A higher mid-childhood height velocity was related to a modestly higher adult FMI in women only (Ptrend=0.0005). CONCLUSIONS: Faster gain in weight and body fat during mid-childhood and puberty appear to be particularly relevant for adult fat mass.

Prospective association of protein intake during puberty with body composition in young adulthood.

OBJECTIVE: To examine the association of habitual animal and plant protein intake during the potentially critical period of puberty with body composition in young adulthood. DESIGN AND METHODS: Multivariable regression analyses were performed on data from 140 female and 122 male participants of the DONALD Study with ≥2 3-day weighed dietary records during puberty (girls 9-14 years; boys 10-15 years) and anthropometric measurements in young adulthood (18-25 years). Fat-free mass index (FFMI) and fat mass index (FMI) were estimated from four skinfolds. RESULTS: In women, a higher pubertal animal protein consumption was independently related to higher levels of FFMI (ptrend = 0.001), but not to FMI (ptrend = 0.5). Adjusted means of FFMI in energy-adjusted tertiles of animal protein intake were 15.3 (95% confidence interval: 15.0, 15.5), 15.4 (15.1, 15.7), 16.2 (15.9, 16.6) kg/m(2) . In men, a higher animal protein intake was related to a higher FFMI (ptrend = 0.04) and a lower FMI (ptrend = 0.001) only after adjusting FFMI for current FMI levels and vice versa. Plant protein was not associated with body composition among either sex. CONCLUSIONS: Our results show that a higher pubertal animal protein consumption may yield a higher fat-free mass in young adulthood.

[Preventability estimates for colorectal and breast cancer in Germany. A methodological evaluation of the risk factors alcohol and overweight]. / Präventionspotenziale für Darm- und Brustkrebs in Deutschland. Eine methodische Evaluation von Schätzungen für die Risikofaktoren Alkohol und Übergewicht.

Population attributable fractions (PAFs) for the risk factors alcohol intake and overweight in the German population were calculated to estimate the preventability of colorectal and breast cancer attributable to these risk factors. Estimates were based on national alcohol consumption and overweight prevalence data in the German population. Comparative analyses were used to evaluate the variation of PAF estimates according to changes in the calculation parameters. PAFs quantify the preventive potential that could result from removing or reducing the risk factor exposure, respectively. Postmenopausal breast cancer was estimated to be preventable by 13-23% if the population were normal weight. Among German men, 10-25% of colon cancers were attributable to alcohol consumption and 7-13% of colorectal cancers to overweight. The comparative analyses demonstrated that preventability estimates vary considerably with the chosen data (risk estimates, reference categories) for PAF calculation and can differ by up to 50%. Thus, data selection should be evidence based, for example, based on meta-analyses, in order to increase the validity of preventability estimates.

Beer consumption and the 'beer belly': scientific basis or common belief?

BACKGROUND/OBJECTIVES: The term 'beer belly' expresses the common belief that beer consumption is a major determinant of waist circumference (WC). We studied the gender-specific associations between beer consumption and WC (partially in relation to body weight and hip circumference (HC) change). PARTICIPANTS/METHODS: Within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study (7876 men, 12 749 women), cross-sectional associations were investigated applying general linear models. Prospective analyses of baseline beer consumption and an 8.5-year WC change were assessed using multivariate general linear models and polytomous logistic regression. To test the site-specific effect of beer consumption on WC, an adjustment for concurrent changes in body weight and HC was carried out. In addition, the relationship between change in beer consumption and change in WC was studied. RESULTS: A positive association in men and no association in women were seen between beer consumption and WC at baseline. Men consuming 1000 ml/d beer were at 17% higher risk for WC gain compared with very light consumers. Significantly lower odds for WC gain (odds ratio=0.88; 95% confidence interval 0.81, 0.96) were found in beer-abstaining women than in very-light-drinking women. The adjustment for concurrent body weight and HC change diminished effect estimates notably, explaining most of the association between beer and change in WC. Decreasing beer consumption was related to higher relative odds for WC loss, although not statistically significant. CONCLUSIONS: Beer consumption leads to WC gain, which is closely related to concurrent overall weight gain. This study does not support the common belief of a site-specific effect of beer on the abdomen, the beer belly.

Relation between hydration status in children and their dietary profile - results from the DONALD study.

OBJECTIVE: To describe associations between hydration status and dietary behaviour in children, as current research indicates that hydration status is influenced by nutrition vice versa, hydration status may influence dietary behaviour. DESIGN: Cross-sectional analyses of data from the Dortmund Nutritional and Anthropometric Longitudinally Designed Study, (DONALD) using 24-h urine samples to determine the hydration status and 3-day weighed food records to describe the dietary profile of the children. SETTING: Secondary analyses of data from an observational study. SUBJECTS: A group of 4-11 year old children living in Dortmund, Germany; N=717. METHODS: Hydration status was determined by calculating the 'free water reserve', using analyses of the 24-h urine samples. Nutrient intake per day was calculated from the 3-day weighed food records. Children were categorized into groups of hydration status and analysed for significant differences in their dietary profile. RESULTS: Children in the highest group of the hydration status had significant higher total water intake, lower energy density of the diet and a lower proportion of metabolic water compared to children in the lowest group of the hydration status. In addition, analyses showed - although not significant in all subgroups - that better hydrated children consumed more water from beverages and water-supplying foods and less energy from fat. CONCLUSIONS: Euhydrated children, that are children in the highest group of hydration status, had a more preferable dietary profile than children at risk of insufficient hydration. SPONSORSHIP: Funding for the DONALD Study and its analyses is provided by the Ministry of Innovation, Science, Research and Technology of the State of North Rhine-Westphalia, Germany.

The influence of habitual protein intake in early childhood on BMI and age at adiposity rebound: results from the DONALD Study.

OBJECTIVE: To analyse the influence of habitual protein intake in early childhood on age and body mass index (BMI) at adiposity rebound (AR), a potential critical period for the development of obesity. SUBJECTS: A total of 313 children (161 boys, 152 girls) participating in the Dortmund Nutritional and Anthropometric Longitudinally Designed Study. METHODS: Weighted summary indices were created reflecting habitual, energy-adjusted protein intake (expressed as % of energy) and protein intake per kg reference body weight per day (g/kg RBW/day) between the age of 12 and 24 months. Body mass index standard deviation scores (BMI-SDS), age at AR and covariates (mother's BMI, gestational age, breastfeeding and siblings) were included in the final models. RESULTS: After adjusting for potential confounders, girls in the highest tertile (T3) of habitual energy-adjusted protein intake had a significantly higher BMI-SDS at AR than those in T1 (T1: -0.61 (95% CI: -0.90; -0.31), T2: -0.49 (-0.79; -0.20), T3: -0.08 (-0.36; 0.20), P for difference=0.01). A comparable association existed with habitual protein intake expressed as g/kg RBW/day (T1: -0.64 (-0.93; -0.36), T2: -0.22 (-0.52; 0.09), T3: -0.25 (-0.54; 0.04), P=0.04). In boys, there were no differences in BMI-SDS at AR between tertiles of habitual protein intake (% of energy or g/kg RBW/day) (P>0.05). Boys in the lowest tertile of habitual energy-adjusted protein intake tended to experience a later AR (T1: 6.0 (5.6; 6.4), T2: 5.5 (5.1; 5.9), T3: 5.4 (5.0; 5.9) years, P=0.07). But neither in girls nor in boys was age at AR significantly different between tertiles of habitual protein intake (% of energy or g/kg RBW/day) (P>0.05). CONCLUSION: A higher habitual protein intake between the age of 12 and 24 months was associated with a higher BMI-SDS at AR in girls, but not in boys. There was no consistent relation between habitual protein intake in early childhood and timing of AR.

A comparative evaluation of two different approaches to estimating age at adiposity rebound.

OBJECTIVE: To compare different approaches (visual estimation of individual BMI curves with polynomial models) to estimate age at adiposity rebound (AR), as different approaches might lead to different results. AR has been suggested as a critical period between intra-uterine life and early adulthood, and recent data showed that early age at AR is associated with higher body mass later in life. METHODS: Longitudinal anthropometric data from the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study were used to obtain individual BMI growth curves. We then compared the visual estimation approach to polynomial models in three different scenarios reflected by different data sets: an idealistic, an realistic, and a realistic scenario with imputed values. RESULTS: In all three scenarios, the visual estimation yielded significantly higher estimates than the polynomial models of 2nd or 3rd order. Cross-tabulations of groups of age at AR (early, medium, and late) showed that truly concordant classification was low, ranging only from 51 to 63%. A closer examination of the data indicated that the differences in estimates were mainly due to differences in the underlying definitions: the polynomial models select the nadir in the growth curve as the age at AR, whereas the visual estimation deviates from this concept in those cases where there is plateau in the growth curve. In the latter instance, the turning point of the growth curve before its increase is selected as the age at rebound. CONCLUSIONS: Estimating AR with the visual approach appears to best reflect the physiological basis of the AR, and is also preferable, because it resulted in the lowest number of children with missing estimates for age at AR. Only when the underlying criteria for the estimation of AR with the visual approach were modified, could concordant results between the two approaches be obtained. Considering the underlying physiological basis, it became clear that approaches which determine AR by simply identifying the nadir in the BMI curve do not reflect AR appropriately. This refers to those cases in which the nadir in the growth curve and the turning point at the onset of the adiposity increase are not identical.

Associations of short-term weight changes and weight cycling with incidence of essential hypertension in the EPIC-Potsdam Study.

The aim of this study was to examine the relationships of short-term weight gain, weight loss, and weight cycling on the odds of developing hypertension. Normotensive middle-aged German men and women (n=12,362) of the European Prospective Investigation into Cancer and Nutrition-Potsdam Study were assigned to categories of 2-year short-term weight changes that were self-reported to have occurred prior to recruitment into the study (gain only, loss only, weight cycling, stable). After 2 years of follow-up after recruitment, 180 cases of incident essential hypertension were identified. In logistic regression models, odds ratios were estimated for the associations between short-term weight changes and risk of developing hypertension. Obesity status (BMI>or=30 or BMI<30 kg/m2) modified the associations between short-term weight change and incidence of diagnosed hypertension. Among obese individuals, short-term weight gain occurring during the 2 years prior to recruitment (OR=2.79, 95% CI 1.19-6.56), weight loss (OR=6.74, 95% CI 2.58-17.6) and weight cycling (OR=4.29, 95% CI 1.55-11.9) were strongly positively associated with incident hypertension, adjusted for age and gender, compared to obese individuals with short-term stable weight. No significant associations between short-term weight changes and risk of diagnosed hypertension were detected among non-obese individuals. Short-term weight changes appeared to present strong risk factors for developing hypertension among obese individuals. The effect seen for weight cycling supports the hypothesis that weight cycling increases the risk of hypertension. The finding for short-term weight loss may be explained by subsequent weight regain and needs further investigation.

Differences between recumbent length and stature measurement in groups of 2- and 3-y-old children and its relevance for the use of European body mass index references.

OBJECTIVE: To compare length and stature measurements of young children and to examine the relevance of any difference for comparison with body mass index (BMI) references designed for use from birth to adulthood. SUBJECTS: A total of 426 2-y-old and 525 3-y-old children included in the Dortmund Nutritional and Anthropometrical Longitudinally Designed (DONALD) Study. DATA ANALYSIS: Length and stature were measured to the nearest millimetre using a stadiometre. Agreement between both measurements at age 2 and 3 y, respectively, was determined by mean differences and by comparison with the German BMI reference. RESULTS: The average length of 2-y-old girls and boys was 88.3 (3.1) and 89.9 (3.2) cm, mean differences (stature minus length) were -0.47 (0.65) and -0.45 (0.64) cm. The corresponding BMI values were 16.18 (1.3) and 16.46 (1.2) kg/m2, with mean differences of +0.17 (0.24) and +0.16 (0.23). According to stature, 9.4% of the girls and 10.8% of the boys were overweight (>90th percentile), while length classified 7.1 and 9.4% as overweight. Similar mean differences between length and stature were observed at age 3 y: -0.53 (0.62) and -0.47 (0.65) cm in height and +0.17 (0.20) and +0.14 (0.20) kg/m2 in the BMI of girls and boys, respectively. According to stature, 7.6 and 7.3% were overweight as opposed to 5.4 and 4.8% using length. The observed differences increased with higher BMI levels. CONCLUSION: Changing measurements from length to stature results in an upward shift of BMI, not reflected in current European BMI references. This small but systematic error may result in misinterpretation of individual BMI levels or trend observations.

[The problem of response in epidemiologic studies in Germany (Part II)]. / Zum Problem der Response in epidemiologischen Studien in Deutschland (Teil II).

The first part of this paper introduced various definitions of response and discussed their significance in the context of different study types. This second part addresses incentives as a method to increase response and evaluates the impact of non response or delayed response on the validity of the study results. Recruitment aims at minimising the proportion of refusal. To achieve this, incentives can be used and potential participants can be contacted in a sequence of increasing intensity. The effectiveness of different incentives was investigated within the pretest of the German survey on children and adolescents by the Robert Koch Institute. A low response is often interpreted in terms of non-response bias. This assumption, however, is as incorrect as would be opposite conclusion, that a high response guarantees valid results. Any study of the influence of nonresponse requires information on non-responders. The comparison between early and late responders as an indirect method to evaluate systematic differences between participants and non-participants by wave analysis is demonstrated within the Northern Germany Leukaemia and Lymphoma study (NLL). The German guidelines for Good Epidemiologic Practice recommend to solicit a minimum of information on the principal hypotheses of a study from non-participants. The example of a population-based health survey (Cooperative Health Research in the Region of Augsburg, KORA) illustrates how information on non-responders within a quantitative non-responder analysis can be achieved and used for the estimation of prevalences. Recommendations how to deal with the response in epidemiological studies in Germany are suggested.

The bone mass concept: problems in short stature.

Bone densitometry is currently one of the mainstays in the evaluation of systemic bone diseases in adults and is also increasingly used to assess primary or secondary bone disorders in children and adolescents. The purpose of carrying out densitometric studies in such circumstances is to measure the densitometric indicators of bone stability. Following procedures which were established for diagnosing adult osteoporosis, a decrease in densitometric surrogates of bone stability is usually interpreted as indicating increased fracture risk. The most basic densitometric parameter is bone mineral content (BMC), which can be measured with most densitometric techniques. BMC is either defined as the mass of mineral contained in an entire bone or as the mass of mineral per unit bone length. While mineral mass can be expected to be a good surrogate for bone stability, BMC is obviously a size-dependent parameter, since small bones weigh less than big bones. This is a drawback in paediatric use, since many children and adolescents who are examined by densitometry suffer from chronic disorders and are small-for-age. Short children will have a lower BMC than their healthy age-matched peers, even if their (smaller) bones are otherwise completely normal.

[Nutrition of children and adolescents. Results of the DONALD Study]. / Kinderernährung in Deutschland. Ergebnisse der DONALD-Studie.

In this paper, the actual diet of children and adolescents is characterized by food group intake. Age-dependent dietary patterns and long-term dietary trends are described and commented on against the background of the optimized mixed diet, a preventive total diet concept for German children and adolescents. Dietary intake data come from 3-day dietary records obtained in the DONALD Study (Dortmund Nutritional and Anthropometrical Longitudinally Designed Study), an ongoing mixed longitudinal cohort study conducted at the Research Institute of Child Nutrition since 1985. The actual diet of the observed children and adolescents differed to some extent from the optimized mixed diet. For example, the intake of vegetables was lower and the intake of meat/sausage and confectionary was higher than recommended. The three rules for food selection of the optimized mixed diet (consume plant foods and beverages liberally, animal foods moderately, and high-fat, high-sugar foods occasionally) show a practical way to improve unfavorable dietary habits of children and adolescents without fundamental changes of food intake patterns and taste properties of the actual diet. The partly favorable and partly unfavorable dietary trends observed in the DONALD Study should continue to be critically considered.

[The problem of response in epidemiological studies in Germany (part I)]. / Zum Problem der Response in epidemiologischen Studien in Deutschland (Teil I).

To achieve high response rates in German epidemiological studies is growing more difficult. Low response in epidemiological studies may decrease the acceptance of the results. Response, however, is not identical with the quality of a study. In the first part of this paper various definitions of response (contact, cooperation, response, recruitment proportions) are introduced and discussed in the context of different study designs with reference to practical examples. A population-based survey such as the Study of Health in Pomerania (SHIP) investigates the distribution of risk factors and health-related endpoints. Surveys should yield representative results which can be generalised to apply to the entire population (external validity). This study design usually requires large participitation proportions. In a prospective cohort study such as the European Investigation into Cancer and Nutrition (EPIC) the emphasis is on internal validity. A stable study population willing to participate in regular follow-ups is a primary recruitment goal. If the response in a case-control study such as the Northern Germany Leukaemia and Lymphoma Study (NLL) is low, the priority is to achieve approximately equal response proportions for cases and controls. Simultaneous public relation and media activities can improve participitation in a study. Multidimensional strategies combining public communications, cooperation with local and regional officials and frequent press and media coverage are emphasised. The second part of this paper will discuss methods to quantify the effects of the response proportions on the validity of the study results.

History of the concept of 'levels of evidence' and their current status in relation to primary prevention through lifestyle interventions.

Primary prevention is a major option to reduce the burden of chronic disease in populations. Because lifestyle interventions have proved to be effective, lifestyle recommendations including nutritional advice are made abundantly. However, both their credibility and their effectiveness are often considered not to be high. Therefore, scientific evidence should form the basis of recommendations and, as in clinical medicine, a rational approach should be followed for the evaluation of evidence. In this paper, the development and current concepts of 'levels of evidence' as they are applied in clinical medicine are outlined and their impact on evidence-based recommendations is discussed. Next, the question is raised as to how far the existing schemes are applicable to the evaluation of issues pertaining to primary prevention through lifestyle changes. Current schemes were developed mainly for clinical research questions and therefore place major emphasis on randomised controlled trials as the main and most convincing evidence in the evaluation process. These types of study are rarely available for lifestyle-related factors and might even not be feasible to obtain. Arguments are advanced to support the notion that a modification of currently existing 'levels of evidence' as developed for clinical research questions might be necessary. Thereby, one might be able to accommodate the specific aspects of evidence-related issues of recommendations for primary prevention through lifestyle changes, like dietary changes.

Time trends in cigarette smoking in two German cohorts--results from EPIC Germany.

Smoking prevention is less advanced in Germany compared with other European and North American countries, and fewer data exist, especially on the consumption habits at the individual level over time. EPIC Germany, which is part of a European multicentre study on diet and cancer, collected data on individual smoking behaviour and allows for consideration of the changing consumption pattern for both centres and different age groups. Within EPIC 25 546 and 27 548 participants, respectively, were recruited in Heidelberg and Potsdam. Data on smoking habits were collected by means of a computer-guided interview during the baseline examination between 1994 and 1998. For each birth cohort smoking prevalence and mean number of cigarettes smoked per day at different ages were calculated. Additionally, the prevalence of non-filter cigarette smoking was computed. Smoking prevalence in the 1990s was still higher among men (Heidelberg 16.3-32.3%; Potsdam 18.2-29.3%) than among women (Heidelberg 12.8-32.0%; Potsdam 10.4-27.8%). However, the percentage of women smokers was still increasing. Filter cigarettes comprised a growing percentage of the cigarettes smoked, but especially among men differences between both German cohorts can still be seen: depending on age, 10.0-12.7% of men in the Heidelberg cohort smoked non-filter cigarettes, but only 1.1-2.3% in the Potsdam cohort. The quantity smoked was higher in the Heidelberg than in the Potsdam cohort with respect to the mean number of cigarettes smoked per day as well as the pack-years of smoking. In conclusion, smoking habits in the Potsdam and the Heidelberg cohorts did not strongly differ by smoking prevalence. However, they did differ according to the quantity and quality of smoking. These differences, as well as the changes over the last 40 years may contribute to a changing pattern of diseases in different groups of the German population.

Recent weight changes and weight cycling as predictors of subsequent two year weight change in a middle-aged cohort.

OBJECTIVE: To evaluate the influence of recent weight changes (weight gain, loss and cycling) on subsequent weight changes. DESIGN: Prospective cohort study with 2 y of follow-up. Data analysis with a polytomous logistic regression model. SUBJECTS: A total of 18 001 non-smoking subjects, 6689 men and 11 312 women, from the general population. MEASUREMENTS: Body height and weight measurements and interview data on lifestyle habits and medical history at baseline. For follow-up, self-administered questionnaires for assessment of body weight and incident diseases. RESULTS: Recent changes in body weight, that is weight gain, weight loss and weight cycling, were significant predictors of subsequent weight changes in both men and women after controlling for age, baseline BMI and several lifestyle and behavioural characteristics as potential confounding factors. Weight cycling before baseline was the strongest predictor of subsequent large weight gain (> or =2 kg) with an odds ratio (OR) of 4.84 (95% confidence interval (CI) 3.34-7.02) in men. In women, prior weight loss was the strongest predictor of subsequent large weight gain (OR 4.77; 95% CI 3.63-6.03), followed by weight cycling (OR 3.02; 95% CI 2.15-4.25). CONCLUSION: These data indicate the need for thorough weight history assessment to identify those who are most likely to gain weight. Effective weight control before the development of obesity or after intentional weight loss due to obesity should be a primary goal in the management of obesity.

[Biological markers in epidemiology: concepts, applications, perspectives (part I)]. / Biologische Marker in der Epidemiologie: Begriffe, Anwendungen, Perspektiven (Teil I).

The inclusion of biomarkers in epidemiological research provides new possibilities for exposure assessment and the study of early structural or functional changes and pre-clinical stages of diseases. At the same time issues of validity, reliability, and quality control as well as logistics require special attention. Usually epidemiological studies become more expensive with regard to time and cost. Interdisciplinary collaboration between epidemiology, basic research, and laboratory research is crucial. A prerequisite for this collaboration are agreements on definitions, methods and procedures. The definition of "biomarker" and a description of previous uses of biomarkers in epidemiological studies are presented in the first part of this paper. The second part addresses genetic markers and markers of individual sensitivity and susceptibility. We will end with a discussion about the possible future of biomarkers in epidemiology.