Invasive procedures and risk of brain abscess: a nationwide, population-based case-control study

It is unknown whether invasive procedures are associated with brain abscess. Nationwide, population-based, matched case–control study of patients with culture verified brain abscess in Denmark from 1989 to 2016. Exposure was invasive procedures 0–6 months before study inclusion. We identified 435 patients and 3909 controls. The level of comorbidity was higher among patients with brain abscess than among controls. A total of 48 cases (11%) had one or more invasive procedures 0–6 months before study inclusion (adjusted odds ratios (aOR) of 3.6 (95% confidence interval (CI): 2.5–5.1), a population attributable fractions of 8% (95% CI: 7–9)). In primary care, ear, nose and throat (ENT) procedures were associated with brain abscess (aOR of 4.0 (95% CI: 2.0–8.0)), but gastrointestinal endoscopies were not (aOR of 1.0 (95% CI: 0.3–3.2)). No bronchoscopies were performed in primary care. In the hospital-based setting, ENT procedures, bronchoscopies and gastrointestinal endoscopies were associated with an increased risk of brain abscess (aOR of 14.5 (95% CI: 4.8–43.8), 20.3 (95% CI: 3.8–110.1) and 3.4 (95% CI: 2.0–5.6), respectively). The association between invasive procedures and brain abscess was more pronounced in the hospital-based setting than in primary care.