Background: Atherosclerotic risk factors (ARF) are known causes of stroke and acute myocardial infarction (AMI) in older adults. However, their role in young adult stroke incidence is largely unknown.
Hypothesis: We hypothesized that if the trend in incidence of young adult strokes is driven by premature atherosclerosis then we would observe similar trends in young adult AMI.
Methods: A 10% random sample of all enrollees, from a commercial claims database between 2001-2014, was used. Enrollees were divide into ages 15 to 45 for young adults and 55 to 75 for older adults. Individual claims for first ever stroke or AMI hospitalizations were identified using ICD-9 and ICD-10 codes. Annual incidence rate was adjusted for age in both groups. A simple linear regression model was used to plot trend lines for incidence.
Results: Included in the analysis were 3,770,474 young adults with mean age 28 and 1,552,351 older adults with mean age 60. Of all young adults, there were 3,078 strokes and 3,408 AMIs compared to 38,707 strokes and 26,094 AMIs in older adults. Both older adult stroke and AMI incidence showed an annual decline with 36.8 and 21.9 less cases per 100,000 enrollees, respectively (R2 = 0.85 and 0.81). Young adult stroke showed a slight increase in incidence overtime with overall, with 0.29 more cases a year per 100,000 enrollees (R2 = 0.24). Meanwhile, young adult AMI incidence showed a slight decline overtime with 0.19 less cases a year per 100,000 enrollees (R2 = 0.139). Though neither change was significantly different from 0, taken together their slopes are different from each other with p = 0.035.
Conclusion: Despite the decreasing incidence of stroke and AMI in older adults, young strokes and AMI incidence remain largely unchanged. The slightly divergent trends between young adult stroke and AMI suggest that there may be more than atherosclerosis at play that is driving the increased incidence young adult strokes, which have been observed in other studies.