The Danish Symptom Cohort was established to investigate symptom experience in the general population and healthcare-seeking in relation to general practice. According to the random sample selected from the Danish population, the cohort included both healthy people and people with diseases. Several articles have been published with data from the cohort.23–25 The focus of the present study was symptom burden in people with multimorbidity and variables for the study were selected accordingly.23 The median age of the participants in the Danish Symptom Cohort was 52 years (IQR 40–64) and for non-participants it was 50 years (IQR 36–67). The respondents were reasonably representative of the study sample, but non-respondents were more often men, unmarried, with lower education, lower income level and with a generally looser attachment to the labour market.

The survey consisted of a web-based questionnaire supported by a telephone interviewer if warranted. The questionnaire was electronic and designed so that it was not possible to skip items, and therefore there were no missing values for those who completed it. The process of developing the questionnaire has been described by Rasmussen et al.15 The questionnaire had five domains: three about experience of symptoms and how participants acted on them, and two about factors related to symptom experience and healthcare-seeking behaviour (online supplemental file 1). The questionnaire included 38 general symptoms, as well as 2 specific symptoms for men and 4 for women (44 symptoms in total). The first sentence in the questionnaire was ‘We are interested to hear if you have experienced any bodily sensations, symptoms, or discomfort within the last four weeks’. For the general symptoms the following phrase was used: ‘Have you experienced any of these within the last 4 weeks?’ Respondents had the opportunity to tick more than one box in a list presenting the 38 general symptoms (online supplemental file 1). Eight symptoms were excluded in the present analyses as six of them were gender-specific (as mentioned above) and would have made comparisons between men and women difficult, and two symptoms ‘coughing up blood’ and ‘blood in vomit’ had low prevalence in the data. Therefore, we included 36 symptoms in the analyses (online supplemental file 2).


The questionnaire also included questions about how each symptom affected usual daily activities (impairment score) and the participant’s concern about each symptom (worry score): ‘Within the last 4 weeks, to what extent did you experience that the following symptoms or discomfort interfered with your usual daily activities?’ and ‘Within the last 4 weeks, to what extent were you concerned about the following symptoms or discomfort?’ For each symptom, there were five response categories: ‘not at all’, ‘slightly’, ‘moderate’, ‘quite a bit’ and ‘extremely’. The response categories were transformed into a numeric scale (0–4), where the experience rated 4 is worse than the experience rated 1.