Association of Younger vs Older Ages With Changes in Incidence of Stroke and Other Vascular Events, 2002-2018

IMPORTANCE Some studies have reported increasing stroke incidence at younger ages (<55 years) but have often relied only on administrative data, and more population-based studies of adjudicated stroke are required. An understanding of the drivers of any increase in incidence of young stroke also requires comparisons with stroke trends at older ages and with trends in incidence of other vascular events at younger ages. OBJECTIVE To determine temporal changes in incidence of stroke and other major vascular events at younger vs older ages. DESIGN, SETTING, AND PARTICIPANTS Prospective population based incidence study conducted from April 2002 to March 2018 with a mean catchment population of 94 567 in Oxfordshire, England. EXPOSURES Calendar time, premorbid vascular risk factors, and occupation. MAIN OUTCOMES AND MEASURES Changes in incidence of stroke, transient ischemic attack (TIA), and other major vascular events (myocardial infarction, sudden cardiac death, and peripheral vascular events) stratified by age, sex, diagnostic workup, etiology, and severity. RESULTS A total of 2429 incident strokes were ascertained (mean age, 73.6 [SD, 14.4] years; 51.3% female). From 2002-2010 to 2010-2018, stroke incidence increased significantly among participants younger than 55 years (incidence rate ratio [IRR], 1.67; 95% CI, 1.31-2.14) but fell significantly among participants aged 55 years or older (IRR, 0.85; 95% CI, 0.78-0.92; P < .001 for difference). The significant increase in incidence at younger than 55 years was independent of sex, stroke severity, pathological subtype, and changes in investigation and was also seen for TIA (IRR, 1.87; 95% CI, 1.36-2.57) but not for myocardial infarction and other major vascular events (IRR, 0.73; 95% CI, 0.58-0.93). Although TIA and stroke at younger than 55 years were significantly associated with diabetes (risk ratio [RR], 3.47; 95% CI, 2.54-4.74). hypertension (RR, 2.52; 95% CI, 2.04-3.12), current smoking (RR. 2.38; 95% CI, 1.92-2.94), and obesity (RR, 1.36; 95% CI. 1.07-1.72), the significant increase in incidence from 2002-2010 to 2010-2018 was still seen in individuals without these risk factors. The increase was greatest in professional/managerial occupations (IRR, 2.52; 95% CI, 1.75-3.62) and least in partially skilled/unskilled occupations (IRR, 1.17; 95% CI, 0.79-1.74). The proportion of TIAs and strokes among those younger than 55 years without known vascular risk factors increased significantly over time (45 [30.4%) vs 115 [42.4%); absolute difference, 12.0%; 95% CI, 2.6-21.5), especially in patients with cryptogenic events (10 [18.5%) vs 63 [49.2%]; absolute difference, 30.7%; 95% CI, 17.2-44.2; P < .001; P = .002 for heterogeneity). CONCLUSIONS AND RELEVANCE Comparing persons living in Oxfordshire, England, in 2002-2010 vs 2010-2018, there was a significant increase in stroke incidence in those younger than 55 years, but a decrease in those aged 55 years or older. Given the absence of this divergence for other vascular events, further research is needed to understand the causes of this difference.