BACKGROUND AND PURPOSE:

• Transient ischemic attack (TIA) is a strong predictor of impending stroke, allowing for management and preventative interventions
• Lioutas et al. (JAMA, 2021) examined population-based incidence of TIA and the timing and long-term trends of stroke risk following TIA

METHODS:

• Retrospective cohort study
• Data source
  • Framingham Heart Study (a prospective cohort study)
• Participants
  • Individuals with no history of TIA or stroke at baseline
  • Followed up from 1948 to December 31, 2017
• Exposures
  • Calendar time: TIA incidence calculation, time-trends analyses
  • TIA: Matched longitudinal cohort
• Study design
  • TIA-free participants were matched 5:1 to participants with first incidence TIA on age and sex
• Primary outcomes
  • TIA incidence rates
  • Proportion of stroke occurring after TIA in the short term (7, 30, and 90 days) vs the long term (>1 to10 years)
  • Stroke after TIA vs stroke among matched control participants without TIA
  • Time trends of stroke risk at 90 days after TIA assessed in 3 epochs: 1954 to 1985 | 1986 to 1999 | 2000 to 2017

RESULTS:

• 14,059 participants | 66 years of follow-up | 366,209 person-years
  • Experienced TIA: 435 participants
    • 53% women; mean age 73.47 years
    • 47% men; mean age 70.10 years
  • Control: 2175 participants
• Estimated incidence rate of TIA: 1.19/1000 person-years
• After TIA, 29.5% of participants had a stroke (median 8.86 years of follow-up)
• Time to stroke after TIA
  • Within 7 days: 21.5%
  • Within 30 days: 30.8%
  • Within 90 days: 39.2%
  • >1 year after the index TIA: 48.5%
  • Median time to stroke was 1.64 (IQR 0.07 to 6.6) years
• The age- and sex-adjusted cumulative 10-year hazard of incident stroke
  • With TIA: Hazard ratio (HR) 0.46 (95% CI, 0.39 to 0.55)
  • Without TIA: HR 0.09 (95% CI, 0.08 to 0.11)
• Fully adjusted HR 4.37 (95% CI, 3.30 to 5.71; P < 0.001)
• 90-day risk of stroke after TIA by time epoch
  • Risk in 1948 to 1985: 16.7% (26 stokes in 155 TIA patients)
  • Risk in 1986 to 1999: 11.1% (18 strokes in 162 patients)
  • Risk in 2000 to 2017: 5.9% (7 strokes in 118 patients)
• Compared with the first epoch, the HR for 90-day risk of stroke has been declining (P = 0.005 for trend)
  • Second epoch: 0.60 (95% CI, 0.33 to 1.12)
  • Third epoch: 0.32 (95% CI, 0.14 to 0.75)

CONCLUSION:

• Risk of stroke was significantly increased after TIA even after accounting for confounding cardiovascular risk factors
  • Patients with TIA require “vigorous surveillance beyond the early, high-risk period and with special attention to hypertension monitoring and treatment”
• The risk of stroke following TIA is decreasing over time, even though the population is aging
• The authors state

1- and 5-year risks of post TIA stroke in the 2000-2017 era are 7.6% and 16.1%, respectively, considerably lower than the respective cumulative risks over the entire observation period and closer to modern era estimates

These decreases most likely reflect the effectiveness of secondary prevention interventions such as stricter blood pressure control and administration of antithrombotic medications

Learn More – Primary Sources:

Incidence of Transient Ischemic Attack and Association With Long-term Risk of Stroke

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