"We observed an unequivocal decline in the risk of both short- and long-term stroke: in the most recent years (after 2000) patients were approximately 70% less likely to suffer a stroke following a TIA as compared with the earlier periods of our study (before 1985)," said Dr. Vasileios-Arsenios Lioutas of Beth Israel Deaconess Medical Center, Harvard Medical School, in Boston.
"Although the study was not designed to specifically answer the question 'why' this happened, the logical explanation is that this reflects improvements in diagnostic workup, secondary prevention and improved public awareness," he told Reuters Health by email.
TIA is an "important but often under-recognized and underestimated clinical phenomenon. The symptoms are by definition fleeting, often mild and resolve completely leading many patients to neglect them," Dr. Lioutas said.
"However, previous studies suggest that TIA is associated with considerably high risk of immediate (within the next 7 days) and more long-term stroke. Therefore, it was important to provide accurate estimations of this short- and long-term risk," he explained.
The researchers analyzed data collected from 1948 through 2017 in roughly 14,000 participants in the Framingham Heart Study. They matched 435 people who experienced TIA to 2,175 controls who did not.
During 66 years of follow-up, the estimated incidence rate of TIA was 1.19 per 1,000 person-years.
Compared with age- and sex-matched controls, patients with TIA have a four- to five-fold higher risk of stroke over the 10 years following the TIA, the team reports in JAMA.s
"This holds true even when accounting for differences in vascular risk factors such as hypertension, diabetes, elevated cholesterol, smoking and cardiac disease. Thus, TIA should be taken seriously and the patients receive a full workup and appropriate preventive medications," Dr. Lioutas told Reuters Health.
While about 20% of post-TIA strokes occur within the first week, "a less well recognized feature emerged from our study," Dr. Lioutas said.
"The risk of stroke continues to be elevated beyond the early phase and approximately 50% of the strokes actually occurred >1 year after the TIA. This finding suggests that TIA patients merit continued surveillance and consistent risk factor control in the long term and not just in the first few weeks to months," he said.
Importantly, the data also show a significant decline in risk of stroke after TIA through the years. The 90-day stroke risk after TIA in 1948-1985 was 16.7%, fell to 11.1% between 1986-1999 and further to 5.9% between 2000-2017.
Compared with the first period (1948-1985), the hazard ratio for 90-day risk of stroke in the second period (1986-1999) was 0.60 (95% confidence interval, 0.33 to 1.12) and in the third period it was 0.32 (95% CI, 0.14 to 0.75) (P=0.005 for trend).
"Despite advances in secondary prevention, stroke risk after TIA remains higher compared with risk among TIA-free participants, even after accounting for confounding cardiovascular risk factors," Dr. Lioutas and colleagues conclude in their paper.
"Taken together, these findings suggest that patients with TIA represent a particularly high-risk group in need of vigorous surveillance beyond the early, high-risk period and with special attention to hypertension monitoring and treatment," they add.
Dr. Andrew Rogove, medical director of Stroke Services at South Shore University Hospital in Bay Shore, New York, told Reuters Health by email, "This study provides very encouraging data as it may suggest that improvement in risk factor modification as well as improving our ability to treat, and more importantly avoid, stroke has improved over time."
"One caution with these results is the low number of strokes seen in each group. Hopefully other large databases of patients will show similar results when investigated," said Dr. Rogove, who was not involved in the study.
SOURCE: https://bit.ly/3omhRQM JAMA, January 26, 2021.
By Megan Brooks
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