Data quality in epidemiological studies is a basic requirement for good scientific research. The aim of this study was to examine an important indicator of data quality, data completeness, by investigating predictors of missing data.

Baseline data of a cohort study, the population-based Hamburg City Health Study, were used. Missingness was investigated at the levels of a whole research unit, on the two segments of health service utilisation and psychosocial variables, and two sensitive items (income and number of sexual partners). Predictors for missingness were sociodemographic variables, cognitive abilities and the mode of data collection. Associations were estimated using binary and multinomial logistic regression models.

Of 10 000 participants (mean age=62.4 years; 51.1% women), 32.9% had complete data at the unit level, 66.8% had partially missing data and 0.3% missed all items. The highest proportions of missing values were found for income (27.8%) and the number of sexual partners (36.7%). At both the unit, segment and item level, older age, female sex, low education, a foreign mother language and cognitive impairment were significant predictors for missingness.

For analysing population-based data, dealing with missingness is equally important at all levels of analysis. During the design and conduct of the study, the identified groups may be targeted to reach higher levels of data completeness.

There is only a little research on anticipated stigma in the general population, despite evidence of negative consequences with regard to underutilisation of medical testing or treatment. While a lot of instruments focus on the interpersonal dimension of public stigma (i.e., societal attitudes), fewer assess the intrapersonal dimension of anticipated stigma, a belief that stigmatising attitudes will be directed at the self in the future. The objective of this study was to test the applicability and the psychometric properties of an anticipated stigma scale in a population survey on beliefs about irritable bowel syndrome (IBS).

Analyses are based on telephone interviews in a random population sample of 1205 adult individuals in Germany. They were presented with a vignette describing a person with symptoms suggestive of IBS, followed by 10 items assessing anticipated stigma based on a modified version of the Perceived Stigma Scale of IBS.

Results indicate that individuals expected others not to have enough knowledge about symptoms and may ascribe their aetiology to personal behaviour. A first exploratory factor analysis (EFA) yielded two factors. Examination of scree plot and content considerations justified a second EFA specifying a one-factorial solution with Cronbach’s α of 0.80 and satisfactory discriminatory power and mean inter-item correlations.

The applicability of the scale to assess anticipated IBS stigma in the general population using a vignette design was demonstrated. Such assessments can be used as the basis for tailored anti-stigma measures, for example, the communication of specific facts about the development of IBS symptoms.