Cohort profile: the Nordic Antireflux Surgery Cohort (NordASCo).

PURPOSE: To describe a newly created all-Nordic cohort of patients with gastro-oesophageal reflux disease (GORD), entitled the Nordic Antireflux Surgery Cohort (NordASCo), which will be used to compare participants having undergone antireflux surgery with those who have not regarding risk of cancers, other diseases and mortality.

PARTICIPANTS: Included were individuals with a GORD diagnosis recorded in any of the nationwide patient registries in the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) in 1964-2014 (with various start and end years in different countries). Data regarding cancer, other diseases and mortality were retrieved from the nationwide registries for cancer, patients and causes of death, respectively.

FINDINGS TO DATE: The NordASCo includes 945 153 individuals with a diagnosis of GORD. Of these, 48 433 (5.1%) have undergone primary antireflux surgery. Median age at primary antireflux surgery ranged from 47 to 52 years in the different countries. The coding practices of GORD seem to have differed between the Nordic countries.

FUTURE PLANS: The NordASCo will initially be used to analyse the risk of developing known or potential GORD-related cancers, that is, tumours of the oesophagus, stomach, larynx, pharynx and lung, and to evaluate the mortality in the short-term and long-term perspectives. Additionally, the cohort will be used to evaluate the risk of non-malignant respiratory conditions that might be caused by aspiration of gastric contents.