Data on over-indebted individuals (n = 949) from a cross sectional study were considered together with the German National Telephonic Health Interview Survey of the Robert Koch-Institute (n = 8318), which is representative for the German population.
a) German National Telephone Health Interview Survey 2003 conducted by the Robert Koch-Institute (GNT-HIS)
Details on the survey have recently been published [
13]. In brief, the GNT-HIS 2003 is a nationally representative health survey of the adult population in Germany with computer assisted telephone interviews (n = 8318) covering various aspects of diseases, including risk factors, quality of life, health care utilisation and socioeconomic status. The response rate of the GNT-HIS 2003 was 52.3%.
Ethics review board approval was not obtained for these secondary analyses of an existing public access dataset.
b) A cross-sectional study regarding over-indebted individuals (OI-survey)
This study was performed in order to measure the health status of over-indebted individuals and their participation in all aspects of society and their utilization of the health care system. It is a survey on over-indebted residents of the German states Rhineland-Palatinate and Mecklenburg-Western Pomerania. An anonymous survey was organised among clients of debt counselling centres. The survey was carried out by the centres for debt and insolvency counselling of Rhineland-Palatinate and Mecklenburg-Western Pomerania and by the centre for debt counselling of the Johannes Gutenberg-University Mainz in 2006 and 2007. Overall, 949 over-indebted subjects were interviewed (participation rate 39.7%). In the OI-survey we did not use reminder-actions in non-responders. Details on the survey have recently been published [
14]. Ethical committee approval was obtained. Informed consent was waived to assure anonymity.
Socio-demographic parameters (age, sex, income, education), Body-Mass-Index, smoking behaviour and depression were obtained in both surveys and used for the analyses. All participants of the telephonic health survey were categorised as not over-indebted, while all OI-survey-participants were categorised as over-indebted. Although a bias towards the null cannot be ruled out, this procedure was chosen due to lacking information on debts in the telephonic health survey.
Participants with missing data of Body-Mass-Index (GNT-HIS n = 179; OI-survey n = 8) were excluded for analyses. The joint database (GNT-HIS and OI-survey) contained 9080 data records (941 data records of the OI-survey and 8139 data records of GNT-HIS).
Participants' self reports on height and weight were used to calculate the Body-Mass-Index in order to define the target value "overweight" and „obesity“. The WHO classifications for overweight (≥25.0 kg/m
2) and obesity (≥30.0 kg/m
2) were used [
15]. Data on participants without overweight or obesity were used as reference.
The prevalence of overweight and obesity associated with over-indebtedness was calculated.
As potential confounders from the literature sex, age, education, income, depression and smoking habits were considered. In crude analysis, they were a priori coded by using binary dummy variables, to improve understanding.
Proportions and their 95%-confidence intervals of dependent variables and potential confounders were calculated. Corresponding unadjusted odds ratios and their 95 percent confidence limits for the association between overweight or obesity and the potential confounders were calculated by using logistic regression analysis.
In multiple logistic regression analysis, all potential confounding factors were modelled in their original categorical form or by using the original binary dummy variables (sex, smoking). They were hierarchically entered to assess their cumulative influence on the association between the risk factor "over-indebtedness" and overweight/obesity.
All calculations were carried out with the software package SPSS (SPSS Inc., Chicago, Illinois), version 14.0