Central nervous system abscesses and empyemas in England: epidemiological trends over five decades

Abstract

To report on population-based epidemiological trends in central nervous system (CNS) abscesses and empyemas in England over five decades. Trend analyses of age-sex-specific hospital admission and death rates using routinely collected English national hospital discharge records, mortality records, and annual population denominators from 1968 to 2019. Hospital admission rates for CNS abscesses and empyemas were stable in England until the late 1980s. In the last two decades of the study period (1999-2019), first-time admissions increased from 1.24 per 100,000 population in 1999 (95% confidence interval [CI] 1.14-1.35) to 2.86 in 2019 (95% CI 2.72-3.01). Admission rates were highest among infants and older adults, and were higher for males than females. There were small but significant increases in annual mortality rates for CNS abscesses and empyemas over the last two decades of the study period after accounting for population ageing, but mortality remained low at around 0.1-0.2 per 100,000 population. Mortality increased with advancing age; deaths in childhood were extremely rare. Case fatality rates where a relevant diagnosis was recorded as either the underlying or contributing cause were 4.3% and 9.7% respectively. The increase in CNS abscesses and empyemas in England might reflect improved case ascertainment, but the likelihood of a true rise in incidence should be considered.