Background
The aim of this study was to evaluate the clinical outcome of patients with bacterial meningitis following the introduction of dexamethasone treatment in Denmark.

Methods
Adult patients with bacterial meningitis, admitted from 2003–2010 to two different university hospitals, were included retrospectively. Data at clinical presentation, Glasgow outcome scale (GOS), cerebrospinal fluid and blood biochemistry were collected. Relative risk (RR) with 95% confidence interval (CI) was computed by Cox proportional hazard regression analysis.

Results
One hundred and forty-seven patients were included in the study. The population had a median age of 62 years and 31% had an immunosuppressive co-morbidity. Eighty-nine patients had an unfavourable outcome (GOS score = 1–4). Adjuvant treatment with corticosteroids (RR = 0.48; 95% CI = 0.30–0.76) was associated with a favourable outcome (GOS score = 5), while altered mental status (RR = 2.36; 95% CI = 1.17–4.78) and age (RR = 1.03; 95% CI = 1.01–1.04) per year increment was associated with an unfavourable outcome. Adjuvant corticosteroid treatment did not affect short- or long-term survival. Short-term mortality was influenced by age (RR = 1.06; 95% CI = 1.04–1.09). Long-term mortality was influenced by age (RR = 1.06; 95% CI = 1.03–1.08) and female sex (RR = 1.81; 95% CI = 1.05–3.14).

Conclusion
This study indicated that adjuvant corticosteroid treatment in acute bacterial meningitis improves the outcome and can safely be administered in an elderly population with high levels of immunosuppressive co-morbidity.