Tick-borne encephalitis in Slovenia from 2000 to 2004: comparison of the course in adult and elderly patients

Abstract

Objective: To present epidemiological data and clinical characteristics of tick-borne encephalitis (TBE) in adult patients, and to compare findings in the subgroup over the age of 60 years with those aged 60 or under.

Methods: The information for this retrospective study was obtained by review of medical documentation. All patients over 15 years of age hospitalized at the Department of Infectious Diseases, University Medical Center Ljubljana, Slovenia, between 2000 and 2004 with pleocytosis (cerebrospinal fluid leukocyte count >5 x 10(6) cells/l) and the presence of serum IgM antibodies against TBE virus qualified for inclusion in this report. Patients were divided into two groups according to their age (patients over the age of 60 were classified as seniors and those aged 60 or under as adults); the findings in the two groups were compared.

Results: Of 448 patients with TBE, 318 were in the adult group and 130 in the senior group. Males predominated in both groups. A biphasic course of the illness was reported by 56% of patients. There were no significant differences in the majority of clinical parameters in the initial phase of TBE but several distinctions between adults and seniors were found in the second phase of the illness. Adults more often presented with fever, headache, stiff neck and photophobia, whereas seniors more frequently reported fatigue, altered consciousness and decreased muscle strength, these differences indicating a more classic course of TBE in the younger group and a somehow different and more severe acute disease in the older group. More severe acute disease and less favorable outcome in seniors was further corroborated by the occurrence of urine retention (18/318, 5.7% versus 27/130, 20.8%; P < 0.001), frequency of pareses (10/318, 3.1% versus 7/130, 5.4%; P = 0.002) and the need for antiedematous treatment (103/318, 32.4% versus 61/130, 46.9%; P = 0.005), as well as by the duration of treatment, duration of hospital stay and the death rate (0/318 versus 3/130, 2.3%; P = 0.024). Several distinctions were present also in laboratory findings, including higher cerebrospinal fluid leukocyte count in the adults than in the seniors (107 x 10(6) cells/l versus 47 x 10(6) cells/l; P < 0.001).

Conclusion: Direct comparison of the course and outcome of TBE revealed several distinctions between patients over 60 years of age and those aged 60 or under and corroborates previous assumptions that TBE is a more serious illness in the elderly population.