Co-occurrence patterns and related risk factors of ischaemic heart disease and ischaemic stroke across 203 countries and territories: a spatial correspondence and systematic analysis.

Background: Ischaemic heart disease (IHD) and ischaemic stroke are leading causes of death worldwide. Although extensively studied, previous research has predominantly addressed these two diseases in isolation. Comorbidity research faces challenges both at the patient level and in terms of study methods. We aimed to characterise the global co-occurrence pattern of IHD and ischaemic stroke from a spatial perspective and to identify the corresponding risk factors of the comorbidity.

Methods: Using data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 database, we extracted incidence rates of IHD and ischaemic stroke and exposure rates of the 68 most detailed risk factors among individuals aged 25 years or older from 203 countries and territories. Based on the four quartiles of global incidence rates for both diseases, we proposed the comorbidity's co-occurrence patterns and classified the 203 countries or territories into three distinct regions (consistent, IHD-dominant, and ischaemic stroke-dominant areas). We used machine learning and negative binomial regression to screen and quantify the effects of corresponding risk factors and computed the population-attributable fraction and composite risk index to evaluate the global disease burden of IHD and ischaemic stroke.

Findings: 89 countries were classified as consistent, 59 as IHD-dominant, and 55 as ischaemic stroke-dominant. The spatial distribution of the three co-occurrence patterns overlapped with exposure to environmental, dietary, and behavioural risk factors. Nine risk factors were identified and functionally classified into common and specific features. Most countries are simultaneously exposed to the combined effects of multiple risk factors. Overall, 45·43% of IHD incidence and 38·53% of ischaemic stroke incidence is attributable to cumulative exposure to the respective risk factors, with specific combinations and variations of these factors greatly influencing the global disparities and patterns of incidence.

Interpretation: The comorbidity of IHD and ischaemic stroke is a pervasive global health issue. Intervening corresponding modifiable risk factors can fundamentally reduce the global burden of these diseases.

Funding: National High Level Hospital Clinical Research Funding.