Risk Factors for Stroke in the Young (18-45 Years): A Case-Control Analysis of INTERSTROKE Data from 32 Countries.

BACKGROUND: It is not clear whether conventional vascular risk factors are responsible for most strokes in patients younger than 45 years of age. Our objective was to evaluate the association of common risk factors with stroke in individuals under 45 years. METHODS: INTERSTROKE was a case-control study carried out in 32 countries between 2007 and 2015. Patients presenting within 5 days of symptom onset of a first stroke were enrolled as cases. Controls were age and sex matched to cases and had no history of stroke. Cases and controls underwent similar evaluations. Odds ratios (ORs) and population attributable risks (PARs) were calculated to determine the association of various risk factors with all stroke, ischemic stroke, and intracranial hemorrhage, for patients 45 years of age or younger. FINDINGS: 1,582 case-control pairs were included in this analysis. The mean age of this cohort was 38.5 years (SD 6.32). Overall, 71% strokes were ischemic. Cardiac causes {OR: 8.42 (95% confidence interval [CI]: 3.01-23.5)}; binge drinking of alcohol (OR: 5.44 [95% CI: 1.81-16.4]); hypertension (OR: 5.41 [95% CI: 3.40-8.58]); ApoB/ApoA1 ratio (OR: 2.74 [95% CI: 1.69-4.46]); psychosocial stress (OR: 2.33 [95% CI: 1.01-5.41]); smoking (OR: 1.85 [95% CI: 1.17-2.94]); and increased waist-to-hip ratio (OR: 1.69 [95% CI: 1.04-2.75]) were the most important risk factors for ischemic stroke in these young cases. For intracerebral hemorrhage, only hypertension (OR: 9.08 [95% CI: 5.46-15.1]) and binge drinking (OR: 4.06 [95% CI: 1.27-13.0]) were significant risk factors. The strength of association and population attributable risk (PAR) for hypertension increased with age (PAR 23.3% in those <35 years of age, 50.7% in 35-45 years of age). INTERPRETATION: Conventional risk factors such as hypertension, smoking, binge drinking of alcohol, central obesity, cardiac causes, dyslipidemia, and psychosocial stress are important risk factors for stroke in those younger than 45 years of age. Hypertension is the most significant risk factor in all age groups and across all regions and both stroke subtypes. These risk factors should be identified and modified in early adulthood to prevent strokes in young individuals.

Variations in knowledge, awareness and treatment of hypertension and stroke risk by country income level.

OBJECTIVE: Hypertension is the most important modifiable risk factor for stroke globally. We hypothesised that country-income level variations in knowledge, detection and treatment of hypertension may contribute to variations in the association of blood pressure with stroke. METHODS: We undertook a standardised case-control study in 32 countries (INTERSTROKE). Cases were patients with acute first stroke (n=13 462) who were matched by age, sex and site to controls (n=13 483). We evaluated the associations of knowledge, awareness and treatment of hypertension with risk of stroke and its subtypes and whether this varied by gross national income (GNI) of country. We estimated OR and population attributable risk (PAR) associated with treated and untreated hypertension. RESULTS: Hypertension was associated with a graded increase in OR by reducing GNI, ranging from OR 1.92 (99% CI 1.48 to 2.49) to OR 3.27 (2.72 to 3.93) for highest to lowest country-level GNI (p-heterogeneity<0.0001). Untreated hypertension was associated with a higher OR for stroke (OR 5.25; 4.53 to 6.10) than treated hypertension (OR 2.60; 2.32 to 2.91) and younger age of first stroke (61.4 vs 65.4 years; p<0.01). Untreated hypertension was associated with a greater risk of intracerebral haemorrhage (OR 6.95; 5.61 to 8.60) than ischaemic stroke (OR 4.76; 3.99 to 5.68). The PAR associated with untreated hypertension was higher in lower-income regions, PAR 36.3%, 26.3%, 19.8% to 10.4% by increasing GNI of countries. Lifetime non-measurement of blood pressure was associated with stroke (OR 1.80; 1.32 to 2.46). CONCLUSIONS: Deficits in knowledge, detection and treatment of hypertension contribute to higher risk of stroke, younger age of onset and larger proportion of intracerebral haemorrhage in lower-income countries.