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.