Measures of quality control in the German component of the EPIC study. European Prospective Investigation into Cancer and Nutrition

The relation between dietary protein, calcium and bone health in women: results from the EPIC-Potsdam cohort

BACKGROUND/AIMS

The role of dietary protein in bone health is controversial. The objective of the present study was to examine the association between protein intake, dietary calcium, and bone structure measured by broadband ultrasound attenuation (BUA).

METHODS

Our analysis includes 8,178 female study participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) Potsdam Study. Ultrasound bone measurements were performed on the right os calcis, and BUA was determined. Dietary intake was assessed by a standardized food frequency questionnaire. We applied linear regression models to estimate the association between dietary protein and BUA.

RESULTS

After multivariate adjustment, high intake of animal protein was associated with decreased BUA values (beta = -0.03; p = 0.010) whereas high vegetable protein intake was related to an increased BUA (beta = 0.11; p = 0.007). The effect of dietary animal protein on BUA was modified by calcium intake.

CONCLUSION

High consumption of protein from animal origin may be unfavourable, whereas a higher vegetable protein intake may be beneficial for bone health. Our results strengthen the hypothesis that high calcium intake combined with adequate protein intake based on a high ratio of vegetable to animal protein may be protective against osteoporosis.

A homocysteine metabolism-related dietary pattern and the risk of coronary heart disease in two independent German study populations

A biomarker profile of high folate and vitamin B-12 and low plasma homocysteine concentrations reduces the risk of coronary heart disease (CHD) and may be linked to diet. The objectives of the present study were to identify a food pattern related to these biomarkers and to examine its association with CHD risk. Dietary patterns related to biomarker plasma concentrations were constructed from data obtained in the Coronary Risk Factors for Atherosclerosis in Women (CORA) Study (200 cases; 255 controls) using the reduced rank regression statistical method. Risks for CHD with relation to the identified pattern were estimated in the CORA study and in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study with 157 cases of incident myocardial infarction among 26,795 participants. In these 2 German study populations, whole-grain bread, fresh fruit, olive oil, mushrooms, cruciferous vegetables, wine, and nuts contributed the most positively and fried potatoes the most negatively to a dietary pattern that was directly associated with both plasma folate and vitamin B-12 concentrations, but inversely with plasma homocysteine. Multivariate-adjusted relative risks for CHD across increasing quintiles of the food pattern score were 1.0, 0.55, 0.52, 0.58, 0.39 (P for trend = 0.05) in the case-control sample and 1.0, 0.95, 0.75, 0.56, 0.72 (P for trend = 0.041) in the prospective study. The combination of a high intake of whole-grain bread, fresh fruit, olive oil, mushrooms, cruciferous vegetables, wine, and nuts with a low intake of fried potatoes was associated with a favorable biomarker profile of homocysteine metabolism and reduced risk of CHD.

Agreement of self-reported medical history: comparison of an in-person interview with a self-administered questionnaire

PURPOSE

To compare history of 22 different diseases reported during an in-person interview with that reported on a mailed self-administered questionnaire.

METHODS

7841 participants of the European Prospective Investigation into Cancer (EPIC)-Potsdam study. The interview at baseline and the questionnaire at follow-up approximately 2 years later included identical questions about whether the participant had ever had a physician diagnosis of each disease. Incident diagnoses occurring in the interval between the interview and questionnaire were excluded from the analysis.

RESULTS

Agreement between self-report from the interview and from the questionnaire was highest (kappa = 0.83-0.88) for myocardial infarction, cancer and diabetes mellitus; it was lower (kappa = 0.68-0.77) for gout, hypertension, hay fever, asthma, osteoporosis, ulcer of the duodenum, thyroid disease, stroke, and kidney stones, and was lowest (kappa = 0.39-0.59) for chronic gastritis, ulcer of the stomach, cerebral ischemia, benign tumor, inflammatory bowel disease, angina pectoris, hyperlipidemia, rheumatism, colon polyps and skin disease. The poor agreement for less severe or more transient diseases was primarily a result of disease frequently being reported at the interview but not on the questionnaire.

CONCLUSION

Self-administered questionnaires do not generate same information particularly for less severe or transient diseases as personal interviews. For these diseases, self-administered questionnaires are not recommended. Pilot studies that test validity will be necessary.

Inflammatory cytokines and the risk to develop type 2 diabetes: results of the prospective population-based European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study

A subclinical inflammatory reaction has been shown to precede the onset of type 2 (non-insulin-dependent) diabetes. We therefore examined prospectively the effects of the central inflammatory cytokines interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) on the development of type 2 diabetes. We designed a nested case-control study within the prospective population-based European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study including 27,548 individuals. Case subjects were defined to be those who were free of type 2 diabetes at baseline and subsequently developed type 2 diabetes during a 2.3-year follow-up period. A total of 192 cases of incident type 2 diabetes were identified and matched with 384 non-disease-developing control subjects. IL-6 and TNF-alpha levels were found to be elevated in participants with incident type 2 diabetes, whereas IL-1beta plasma levels did not differ between the groups. Analysis of single cytokines revealed IL-6 as an independent predictor of type 2 diabetes after adjustment for age, sex, BMI, waist-to-hip ratio (WHR), sports, smoking status, educational attainment, alcohol consumption, and HbA(1c) (4th vs. the 1st quartile: odds ratio [OR] 2.6, 95% CI 1.2-5.5). The association between TNF-alpha and future type 2 diabetes was no longer significant after adjustment for BMI or WHR. Interestingly, combined analysis of the cytokines revealed a significant interaction between IL-1beta and IL-6. In the fully adjusted model, participants with detectable levels of IL-1beta and elevated levels of IL-6 had an independently increased risk to develop type 2 diabetes (3.3, 1.7-6.8), whereas individuals with increased concentrations of IL-6 but undetectable levels of IL-1beta had no significantly increased risk, both compared with the low-level reference group. These results were confirmed in an analysis including only individuals with HbA(1c) <5.8% at baseline. Our data suggest that the pattern of circulating inflammatory cytokines modifies the risk for type 2 diabetes. In particular, a combined elevation of IL-1beta and IL-6, rather than the isolated elevation of IL-6 alone, independently increases the risk of type 2 diabetes. These data strongly support the hypothesis that a subclinical inflammatory reaction has a role in the pathogenesis of type 2 diabetes.

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.

Recruitment procedures of EPIC-Germany. European Investigation into Cancer and Nutrition

EPIC is among the largest cohort studies, with approximately 475,000 study participants, on the etiological influence of diet and chronic diseases. During a 4-year recruitment period, two German EPIC centers, located in Heidelberg and Potsdam, aimed to recruit a total of 60,000 study participants from the local populations. The recruitment process was based on addresses from general population registries and started 4-5 weeks in advance with an initial invitation by mail to the basic examination for this study. Subjects not responding within 2 weeks were reminded. In Potsdam, this was done by mail and telephone, and in Heidelberg by telephone. During the recruitment phase, from 1994 to 1998, 53,162 subjects in total were examined for the cohort studies in Heidelberg (n = 25,546) and Potsdam (n = 27,616). The participation rate, compared to the invited number of subjects, was 22.7% in Potsdam and 38.3% in Heidelberg, with a considerable variation by municipality and gender. A comparison with data from the National Health Survey 1991/1992 revealed that the cohort populations were of higher socio-economic status and were healthier than the source population. We concluded that the selective participation would help to ensure high maintenance of the cohort during active follow-up. Selective participation does not harm etiological conclusions because disease associations are derived internally as relative risk. The relative risk estimates can be used to calculate population-attributable risk and preventable proportion, based on exposure prevalence derived by surveys and other studies.

Follow-up procedures in EPIC-Germany--data quality aspects. European Prospective Investigation into Cancer and Nutrition

With 475,000 participants throughout Europe, EPIC is one of the largest cohort studies investigating the association between diet and cancer and other chronic diseases. The German part of EPIC comprises about 53,000 participants in Potsdam (n = 27,616) and in Heidelberg (n = 25,546). In the German study centers, follow-up started in 1998 and will be continued in 2-year intervals over the next 10-15 years. To ensure high follow-up data quality at an European level, an international working group developed guidelines for endpoint data collection in every country. A follow-up phase in Germany comprises mailing of a questionnaire, tracing of individuals to whom mail could not be delivered, obtaining information on deceased participants including cause of death, and verifying self- reported diagnoses. Furthermore, activities aimed at motivating study participants are part of the follow-up. The first round of follow-up of those who entered the study in 1994 and 1995 included 8, 706 participants in Potsdam and 6,289 in Heidelberg. Due to a comprehensive and intensive reminder and tracing system, vital status of the study subjects is known from almost 100% in Potsdam and 99% in Heidelberg. Two years after baseline examination, and with twice as many addresses in Potsdam as in Heidelberg, addresses had to be traced or checked via population registry (13 versus 6%). Tracing, the application of different mailing strategies, and intensive reminder activities resulted in a 95% return of the questionnaire in Potsdam and 90% in Heidelberg. The system of follow-up data entry and control, including completion of missing information via telephone, verification of self-reports and causes of death, has been set up for EPIC-Germany and works efficiently and successfully. The aim of this paper is to describe the follow-up procedures in EPIC-Germany with a focus on the generation of valid and complete outcome data.

EPIC-Germany--A source for studies into diet and risk of chronic diseases. European Investigation into Cancer and Nutrition

The 'European Investigation into Cancer and Nutrition (EPIC)' represents one of the main scientific activities of the EU program 'Europe against Cancer' and is a large-scale cohort study on diet and chronic diseases, especially cancer, with approximately 475,000 study participants. The German contribution amounted to 53,000 study participants recruited between 1994 and 1998. The study instruments of the baseline examination included self-administered questionnaires for optical reading, PC-guided interviews, and physical examinations. These instruments covered different aspects of lifestyle, with a particular focus on diet. In addition, about 95% of the participants provided 30 ml of blood. The blood was stored in liquid nitrogen for further use, preferentially in nested case-control studies. All interviews and examinations were conducted by trained interviewers in examination centers established for this study in local health offices. Every 2 years, a follow-up questionnaire is mailed to the study participants. The follow-up questionnaires will be used as the major source of outcome information and to update exposure information. The self-reported diseases are verified by medical data. In the future, record linkage with local cancer registries will help to support the identification and collection of incident cancer cases. Only an outline of hypotheses was formulated at the very beginning of EPIC in 1992. In the future, each etiological study will be based on detailed research hypotheses according to the existing knowledge and identified research gaps. These studies will be conducted on cancer at the international level and on non-cancer diseases at the national or local level.