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.

European cardiovascular guidelines recommend systematic atrial fibrillation (AF) screening in community-dwelling high-risk patients. However, little is known about the impact of abnormal screening findings, including AF and non-AF incidental findings on the target population. This gap highlights the need to assess both the benefits and potential harms from patients’ perspectives to fully understand the impact of AF screening. Therefore, the aim of this study is to explore patients’ experiences with AF screening among those who received abnormal findings from ambulatory ECG monitoring.

We conducted a qualitative study using semistructured interviews, analysed thematically. Participants in the PATCH-AF trial, based in Amsterdam primary care, were purposively sampled based on their screening results (AF or non-AF incidental findings), sex and socioeconomic status.

We achieved data saturation after conducting 16 interviews (6 with interviewees diagnosed with AF and 10 with non-AF incidental findings). Participants had a median age of 76 (73–79) years, and 56% were male. Their experiences, whether positive or negative, fluctuated throughout the screening process and depended on their initial motivations for participation in AF screening (seeking extra health checks, finding explanations for pre-existing symptoms or contributing to medical research), expectations and perceived benefits from clarification, diagnostic workup or treatment. Influencing factors included the type of finding (AF or non-AF incidental finding), healthcare provider communication and individual characteristics such as age, socioeconomic status and medical history.

This qualitative study highlights both positive and negative AF screening experiences from the patients’ perspective. It underscores how patients’ motivations and expectations for participation, the type of ambulatory ECG finding and communication and follow-up by healthcare providers shape their overall experiences. Healthcare providers should be aware of these factors to optimise screening consultations. Clear guidelines on communicating abnormal ambulatory ECG findings, especially incidental findings, are warranted.

The Netherlands Trial Register (NTR) number NL9656.