Temporal trends in cross-country inequalities of stroke and subtypes burden from 1990 to 2021: a secondary analysis of the global burden of disease study 2021

Abstract

Background: Stroke remains a significant global health challenge, with persistent disparities in burden across different countries and regions. This study aimed to assess the temporal trends in cross-country inequalities of stroke and its subtypes burden from 1990 to 2021.

Methods: We conducted a secondary analysis of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021. The age-standardised disability-adjusted life years (DALYs) rate (ASDR) was used to assess the burden of stroke and its subtypes (ischemic stroke, intracerebral haemorrhage, and subarachnoid haemorrhage) across 21 GBD regions and 204 countries. The slope index of inequality (SII) and the concentration index were calculated to quantify the absolute and relative cross-country inequalities in the burden of stroke and its subtypes, with negative values indicating a higher burden in lower socio-demographic index (SDI) countries, and positive values indicating a higher burden in higher SDI countries. Estimated annual percentage change (EAPC) was used to illustrate temporal trends at global and regional levels from 1990 to 2021. The inequality changing patterns from 1990 to 2021 were classified as worsening, improving, and shifting to higher burdens among higher or lower SDI countries.

Findings: From 1990 to 2021, the ASDR of total stroke decreased from 3078.95 (95% uncertainty interval [UI]: 2893.58, 3237.34) to 1886.20 (95% UI: 1738.99, 2017.90) per 100,000 population globally. While both absolute and relative inequalities increased, with a disproportionately higher burden shouldered by countries with lower SDI. The SII of total stroke exhibited a worsening inequality among lower SDI countries, increasing by 286.97 units from -2329.47 (95% confidence interval [CI]: -2857.50, -1801.43) in 1990 to -2616.44 (95% CI: -2987.33, -2245.56) in 2021. Similarly, the concentration index of total stroke increased by 0.03 from -0.0819 (95% CI: -0.1143, -0.0495) in 1990 to -0.1119 (95% CI: -0.1478, -0.0759) in 2021. The changing patterns from 1990 to 2021 were diverse across regions, yet most regions exhibited a worsening inequality among lower SDI countries in both SII and concentration index. Southern Sub-Saharan Africa showed the largest worsening inequality in SII (EAPC: -2.15, 95% CI: -2.71, -1.57) while Central Europe showed the largest worsening inequality in concentration index (EAPC: -0.51, 95% CI: -0.58, -0.44). In 2021, the highest negative SII was observed in Oceania and the highest negative concentration index was in the Caribbean. In terms of subtypes, ischemic stroke reported a worsening inequality among lower SDI countries in SII (EAPC: -2.13, 95% CI: -2.20, -2.05) while intracerebral haemorrhage showed an improving inequality in SII (EAPC: 0.44, 95% CI: 0.40, 0.47). SII in subarachnoid haemorrhage (EAPC: -0.18, 95% CI: -0.19, -0.17) and concentration index in ischemic stroke (EAPC: -0.25, 95% CI: -0.27, -0.23) presented a shift to higher burden among lower SDI countries from 1990 to 2021.

Interpretation: Although the burden of stroke and its subtypes decreased from 1990 to 2021, inequalities have persisted and even widened in some regions. Timely and effective prevention and management strategies for stroke and its subtypes are needed in specific areas to reduce the stroke burden and achieve equity in health outcomes.

Funding: None.

Keywords: Disability-adjusted life years; Global burden of disease; Health inequalities; Stroke; Temporal trends.

Fig. 1

Global maps of ASDR per 100,000 population by stroke and subtypes in 1990 and 2021. Notes: (A1) ASDR of total stroke in 1990. (A2) ASDR of total stroke in 2021. (B1) ASDR of ischemic stroke in 1990. (B2) ASDR of ischemic stroke in 2021. (C1) ASDR of intracerebral haemorrhage in 1990. (C2) ASDR of intracerebral haemorrhage in 2021. (D1) ASDR of subarachnoid haemorrhage in 1990. (D2) ASDR of subarachnoid haemorrhage in 2021. ASDR, age-standardised DALY rate. DALYs, disability-adjusted life years.

Fig. 2

Absolute and relative cross-country inequality in ASDR and rankings of total stroke, 1990–2021. Notes: (A) Health inequality regression curves for ASDR of total stroke. (B) Concentration curves for ASDR of total stroke. (C) Ranking graphs and change patterns for SII and CI of total stroke. Δ, the percentage change of inequality from 1990 to 2021. ASDR, age-standardised DALY rate. DALYs, disability-adjusted life years. SDI, socio-demographic index. SII, slope index of inequality. CI, concentration index. GBD, global burden of disease.

Fig. 3

Absolute and relative cross-country inequality in ASDR and rankings of ischemic stroke, 1990–2021. Notes: (A) Health inequality regression curves for ASDR of ischemic stroke. (B) Concentration curves for ASDR of ischemic stroke. (C) Ranking graphs and change patterns for SII and CI of ischemic stroke. Δ, the percentage change of inequality from 1990 to 2021. ASDR, age-standardised DALY rate. DALYs, disability-adjusted life years. SDI, socio-demographic index. SII, slope index of inequality. CI, concentration index. GBD, global burden of disease.

Fig. 4

Absolute and relative cross-country inequality in ASDR and rankings of intracerebral haemorrhage, 1990–2021. Notes: (A) Health inequality regression curves for ASDR of intracerebral haemorrhage. (B) Concentration curves for ASDR of intracerebral haemorrhage. (C) Ranking graphs and change patterns for SII and CI of intracerebral haemorrhage. Δ, the percentage change of inequality from 1990 to 2021. ASDR, age-standardised DALY rate. DALYs, disability-adjusted life years. SDI, socio-demographic index. SII, slope index of inequality. CI, concentration index. GBD, global burden of disease.

Fig. 5

Absolute and relative cross-country inequality in ASDR and rankings of subarachnoid haemorrhage, 1990–2021. Notes: (A) Health inequality regression curves for ASDR of subarachnoid haemorrhage. (B) Concentration curves for ASDR of subarachnoid haemorrhage. (C) Ranking graphs and change patterns for SII and CI of subarachnoid haemorrhage. Δ, the percentage change of inequality from 1990 to 2021. ASDR, age-standardised DALY rate. DALYs, disability-adjusted life years. SDI, socio-demographic index. SII, slope index of inequality. CI, concentration index. GBD, global burden of disease.