Risk Factors for Brain Abscess: A Nationwide, Population-Based, Nested Case-Control Study

Background. Knowledge on risk factors for brain abscess is limited and relies on single-center cohort studies. Methods. We accessed nationwide medical registries to conduct a population-based, nested case-control study of risk factors for brain abscess. We applied risk-set sampling for the selection of population controls (1:10), who were individually matched by age, sex, and area of residence. Conditional logistic regression was used to compute adjusted odds ratios (aOR) with 95% confidence intervals (CIs). Population-attributable fractions were calculated. Results. We identified 1384 brain abscess patients in Denmark from 1982 through 2016, and 13 839 matched population controls. The median age of patients was 50 years (interquartile range 33-63) and 37% were female. Cases often had Charlson comorbidity scores >2 (16%), compared with controls (3%). Our calculated aORs were 2.15 (95% CI 1.72-2.70) for head trauma; 19.3 (95% CI 14.3-26.0) for neurosurgery; 4.61 (95% CI 3.39-6.26) for dental infections; 2.57 (95% CI 1.71-3.84) for dental surgery; 3.81 (95% CI 3.11-4.67) for ear, nose, and throat infection; 2.85 (95% CI 2.21-3.70) for ear, nose, and throat surgery; 15.6 (95% CI 9.57-25.4) for congenital heart disease; 1.74 (95% CI 1.33-2.29) for diabetes mellitus; 2.22 (95% CI 1.58-3.11) for alcohol abuse; 2.37 (95% CI 1.53-3.68) for liver disease; 2.04 (95% CI 1.30-3.20) for kidney disease and 8.15 (95% CI 3.59-18.5) for lung abscess or bronchiectasis. The aORs were 4.12 (95% CI 3.37-5.04) for solid cancer; 8.77 (95% CI 5.66-13.6) for hematological cancer; 12.0 (95% CI 6.13-23.7) for human immunodeficiency virus; and 5.71 (95% CI 4.22-7.75) for immunomodulating treatments. Population-attributable fractions showed were substantial contributors to the occurrence of brain abscess neurosurgery (12%); solid cancer (11%); ear, nose, and throat infections (7%); and immunomodulating treatments (5%). Conclusions. Important risk factors included neurosurgery; cancer; ear, nose, and throat infections; and immunomodulating treatments.