Incidence and outcomes for stroke in Ulaanbaatar, Mongolia, during 2019-21: a prospective population-based study

Background:In the absence of reliable data to quantify the burden of stroke, we aimed to determine the incidence and outcome of stroke through the conduct of a prospective population-based study in Ulaanbaatar, Mongolia, during 2019-21. Methods:All cases of stroke were identified through surveillance of multiple overlapping sources of hospitalised, ambulatory, and deceased individuals, using standardised diagnostic criteria in adult (aged & GE;16 years) residents of the six urban districts of Ulaanbaatar, Mongolia (population person-years, N=1 896 965) between Jan 1, 2019, and Dec 31, 2020. Data on sociodemography, medical history, and management were collected. Crude and standardised incidence were calculated for first-ever stroke and its major pathological subtypes, and reported with 95% CIs. Outcomes were 28-day case fatality ratios and functional recovery on the modified Rankin scale at 90 days and 1 year. Findings: 3803 strokes in 3738 patients were identified, of which 2962 were first-ever incident cases (mean age 59 years [SD 13], 1161 [39 & BULL;2%] females). Annual incidence of first-ever stroke (per 100 000) was 156 & BULL;1 (95% CI 150 & BULL;5-161 & BULL;8) on a crude basis, 171 & BULL;6 (157 & BULL;5-185 & BULL;6) when age-adjusted to the Mongolian population, and 140 & BULL;3 (136 & BULL;7-143 & BULL;9) when age-adjusted to the world population. World-adjusted incidence of pathological subtypes were 66 & BULL;6 (95% CI 64 & BULL;8-68 & BULL;3) for ischaemic stroke, 54 & BULL;5 (53 & BULL;0-56 & BULL;1) for intracerebral haemorrhage, and 18 & BULL;7 (18 & BULL;3-19 & BULL;1) for subarachnoid haemorrhage. Men were twice as likely to suffer ischaemic stroke and intracerebral haemorrhage as women, but the risks were similar for subarachnoid haemorrhage; these patterns were consistent across age-groups. The predominant risk factors were hypertension seen in 1363 (63 & BULL;1%) of 2161, smoking in 596 (26 & BULL;8%) of 2220, regular alcohol consumption in 533 (24 & BULL;0%) of 2220, obesity in 342 (16 & BULL;1%) of 2125, and diabetes in 282 (12 & BULL;7%) of 2220. There was little use (0 & BULL;9%) of thrombolysis for acute ischaemic stroke, partly due to delays in presentation after the onset of symptoms (median 16 & BULL;0 h [IQR 3 & BULL;0-48 & BULL;0]). The 28-day case-fatality rate was 36 & BULL;1% (95% CI 34 & BULL;3-37 & BULL;9) overall, and 14 & BULL;8% (12 & BULL;8-16 & BULL;7) for ischaemic stroke, 52 & BULL;9% (49 & BULL;9-55 & BULL;8) for intracerebral haemorrhage, and 54 & BULL;3% (49 & BULL;4-59 & BULL;1) for subarachnoid haemorrhage. Corresponding figures for poor functional outcome at 1-year, defined by scores of 3-6 for death or dependency on the mRS, were 61 & BULL;6% (95% CI 59 & BULL;8-63 & BULL;4), 47 & BULL;5% (44 & BULL;7-50 & BULL;3), 77 & BULL;0% (74 & BULL;5-79 & BULL;5), and 61 & BULL;8% (57 & BULL;0-66 & BULL;5), respectively. Interpretation The urban population of Ulaanbaatar, Mongolia, has a high incidence of stroke, particularly for intracerebral haemorrhage and subarachnoid haemorrhage, from which half of patients die within 1 month and more than two-thirds are either dead or dependent at 90 days. Although the overall incidence of stroke is similar to other countries, it occurs at a mean age of 60 years, which is at least 10 years younger than in high-income countries. These epidemiological data can inform the implementation of future programmes and scale-up activities for the primary and secondary prevention of stroke, and in the organisation of systems of care. Funding:Science and Technology Foundation of the Ministry of Education, Culture, and Science of Mongolia and The George Institute for Global Health. Copyright & COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND license.

Automated summary

This study aimed to determine the incidence and outcome of stroke in Ulaanbaatar, Mongolia. The findings showed a high incidence of stroke, particularly for intracerebral hemorrhage and subarachnoid hemorrhage, with a high mortality rate within one month and a high rate of death or dependency at 90 days. These epidemiological data can inform future stroke prevention programs and the organization of care systems.