Following TIA, patients experience ‘particularly high’ early, late risk for stroke

A population-based cohort study from 1948 to 2017 demonstrated a substantially greater risk for stroke following a transient ischemic attack, though that risk decreased significantly from 2000 to 2017 compared with 1948 to 1985.

The study, which was published in JAMA and examined the rate of TIA and the risk for stroke following a TIA in a population-based cohort, also demonstrated an overall estimated crude incidence of TIA of 1.19 per 1,000 person-years.

“TIA is a major herald of impending stroke,” the researchers wrote. “Heightened awareness, identification of persons at high risk, and timely management can significantly mitigate this risk.”

Vasileios-Arsenios Lioutas, MD, a Harvard Medical faculty physician in neurology and vascular neurology, and colleagues gathered data from the Framingham Heart Study for this retrospective analysis. The researchers examined data from patients in the three generations of that study, including the original cohort (enrolled in 1948; 5,209 persons aged 28-62 years), the offspring cohort (enrolled in 1971; 5,124 persons aged 5-70 years) and the third-generation cohort (enrolled in 2002; 4,095 persons aged 19-74 years), all of whom had not had a stroke or TIA. The cohorts were predominately white and of European descent, according to the results from Lioutas and colleagues; they classified the participants as “middle-class and well-educated.”

The main outcome measures included rates of TIA, number of strokes occurring after TIA in the short term (7, 30 and 90 days) compared with the long term (more than 1 to 10 years), stroke after TIA compared with stroke among matched controls who had not had a TIA and time trends in stroke risk at 90 days after TIA in 3 time periods: 1954-1985, 1986-1999 and 2000-2017.

Lioutas and colleagues examined data from 14,059 participants over 66 years of follow-up (366,209 person-years). During that time, they noted 435 TIA, including 229 in women (mean age, 73.47 years) and 206 men (mean age, 70.1 years). The researchers matched these patients with 2,175 controls who did not have a TIA and reported an estimated TIA incidence of 1.19 per 1,000 person-years.

During a median follow-up period of 8.86 years after TIA, 130 patients (29.5%) experienced a stroke. Of these, 28 strokes (21.5%) occurred within 7 days, 40 (30.8%) occurred within 30 days, 51 (39.2%) occurred within 90 days, and 63 (48.5%) occurred more than 1 year after the index TIA. The researchers reported a median time to stroke of 1.64 years (interquartile range, 0.07-6.6 years).

The age- and sex-adjusted cumulative 10-year hazard for incident stroke among patients after a TIA (130 strokes among 435 cases) was 0.46 (95% CI, 0.39-0.55) and 0.09 (95% CI, 0.08-0.11) for matched control participants without TIA (165 strokes among 2,175 participants), for a fully adjusted HR of 4.37 (95% CI, 3.30-5.71). Compared with the 90-day stroke risk following TIA from 1948 to 1985 (16.7%; 26 strokes among 155 patients with TIA), the risk between 1986 and 1999 was 11.1% (18 strokes among 162 patients) and 5.9% (7 strokes among 118 patients) from 2000 to 2017. The HR for 90-day stroke risk in the second period was 0.6 (95% CI, 0.33-1.12) and 0.32 in the third period (95% CI, 0.14-0.75) compared with the first period.

The researchers attributed the downturn in stroke rates during the latter period of the study to “the effectiveness of secondary prevention measures,” including tighter blood pressure control and the use of antithrombotic drugs. However, they noted that stroke risk is higher in patients who experienced a TIA compared with those who did not, even after considering confounding cardiovascular risk factors.

Lioutas and colleagues found that the ensuing rate of stroke continued to rise and deviate from that of participants who did not experience a TIA throughout the entire follow-up period; 49% of strokes happened more than 12 months after the index TIA, a finding that aligns with results from other large longitudinal studies, according to the researchers. They also noted that, apart from higher blood pressure and language symptoms at presentation, no “traditionally recognized” indicators for increased early stroke risk correlated with ensuing early or delayed stroke.

“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,” Lioutas and colleagues wrote.