The Dutch DataPain Study follows chronic pain patients who were referred to the pain clinic of Maastricht University Pain Centre in the Netherlands between 2003 and 2018. The cohort includes patients who were classified as chronic pain sufferers in accordance with the International Association for the Study of Pain criteria, defining chronic pain as pain experienced over a period lasting longer than 3 months. Patients were excluded if their chronic pain was cancer-related (or if informed consent had not been granted). At baseline, almost 60% of the patients were female and 40% above the age of 61. The patients have been followed up routinely and with questionnaires.