The spectrum of acute bacterial meningitis in elderly patients

Background: We conducted a prospective, observational study in Barcelona to determine the epidemiology, clinical features, and outcome of elderly patients with acute bacterial meningitis (ABM) compared with younger adults. Methods: During 1982-2010, all patients with ABM were prospectively evaluated. There were two groups: I (15-64 years) and II (>= 65 years). All patients underwent clinical examination on admission and at discharge following a predefined protocol. Results: We evaluated 635 episodes of ABM. The incidence was 4.03/100,000 (Group I) and 7.40 /100,000 inhabitants/year (Group II) (RR = 1.84; 95%CI: 1.56-2.17, P < 0.0001). Elderly patients had co-morbid conditions more frequently (P < 0.0001) and more frequently lacked fever (P = 0.0625), neck stiffness (P < 0.0001) and skin rash (P < 0.0001), but had an altered level of consciousness more often (P < 0.0001). The interval admission-start of antibiotic therapy was longer for elderly patients (P < 0.0001). Meningococcal meningitis was less frequent in elderly patients (P < 0.0001), whereas listerial (P = 0.0196), gram-negative bacillary (P = 0.0065), and meningitis of unknown origin (P = 0.0076) were more frequent. Elderly patients had a higher number of neurologic (P = 0.0009) and extra-neurologic complications (P < 0.0001). The overall mortality ratio was higher in elderly patients (P < 0.0001). Conclusions: Elderly people are at higher risk of having ABM than younger adults. ABM in the elderly presents with co-morbid conditions, is clinically subtler, has a longer interval admission-antibiotic therapy, and has non-meningococcal etiology. It is associated with an earlier and higher mortality rate than in younger patients.