Case Fatality Rates of Subarachnoid Hemorrhage Are Decreasing with Substantial between-Country Variation: A Systematic Review of Population-Based Studies between 1980 and 2020.

BACKGROUND: The declining prevalence of smoking and hypertension has been associated with the decrease of subarachnoid hemorrhage (SAH) incidence in the 21st century. Since these same risk factors are linked to SAH mortality, the case fatality rate (CFR) of SAH has potentially also decreased during recent decades. Thus, we conducted a systematic review to address SAH CFR changes over the last 40 years.

METHODS: We performed a systematic literature search in OVID Medline, Scopus, and Cochrane Library databases. We focused on population-based studies published between 1980 and 2020 that had included both hospitalized and nonhospitalized SAH cases, and reported 1-month CFRs for at least two individual study periods for the same population. Finally, we used a linear regression analysis to estimate the annual CFR changes in each identified population and pooled the regional changes for larger geographical and sex-specific analyses.

RESULTS: Of the 4,562 initial publications, we included 22 studies (three of which reached a high-quality classification) consisting of 17,593 SAH patients from 16 different populations and 10 countries. Between 1980 and 2020, SAH CFR declined in all but two populations by an average of -1.5%/year. In the continent-based pooled geographical analyses, CFR decline was the most noticeable in North America (-2.4%/year) and Oceania (-2.2%/year). The decline was more moderate in Northern Europe (-0.8%/year) and Southern Europe (-0.7%/year). Overall, CFRs declined both in women (-1.9%/year) and in men (-1.2%/year). When comparing the first and second half of the study period, CFRs declined from 41% to 31%.

CONCLUSION: Short-term SAH CFRs seem to have declined since 1980. Time trends of SAH CFRs can still be identified for only a few populations, and high-quality data are scarce. Whether the observed decline relates to changes in risk factors, treatment outcomes or diagnostics remains to be studied.