Comment

This study is a model of well planned and executed epidemiological research. Lagergren and colleagues conducted a case control study of risk factors for oesophageal adenocarcinoma. They obtained standardised information on personal history, endoscopy, and pathology in 85% of eligible cases of adenocarcinoma in the entire country of Sweden over three years. The strengths of the study design include using two control groups and taking steps to avoid reversed causality. The first control group comprised randomly selected age and sex matched subjects from the entire Swedish population. The second control group comprised patients with squamous oesophageal carcinoma who were not aware of their cancer type, which should exclude recall bias of symptoms compared with those with adenocarcinoma. By limiting recall of reflux symptoms to at least five years before the diagnosis of cancer, the chance that the tumour caused these symptoms was excluded.

Lagergren et al found that reflux had a strong association with oesophageal adenocarcinoma, a …