How often did a second stroke occur after a first?

Researchers used the South London Stroke Register, which followed 5,509 people who had a first-ever stroke between 1995 and 2019. To estimate how often a second stroke occurred, they treated death as a competing event: the cumulative incidence calculation allows for deaths before a second stroke and estimates the proportion of the original group who would have a recurrence by a given time. This gives a population-level picture based on long register follow-up, rather than a prediction for any one person.

Over 34,874 person-years of follow-up, 680 people (12.3%) had a stroke recurrence and 2,666 (48.4%) died. The cumulative recurrence risk was about one in ten within five years: 9.6%. Over longer follow-up, the risk rose further, reaching about 15% by 25 years. In other words, within a group like this, roughly one in ten would have a second stroke in the first five years, and the longer-term risk accumulated slowly from there.

The register also let the researchers identify some characteristics linked to recurrence. After an ischemic stroke, higher recurrence risk was seen in earlier cohorts and in people with hypertension, a prior transient ischemic attack, or no hospital admission. After a hemorrhagic stroke, diabetes was associated with higher recurrence risk. These associations do not change the overall frequency answer, but they point to groups within the cohort that carried more of the recurrence burden.

The five-year estimate of about one in ten is a cohort figure from the South London register; it is not an individual prediction. The people included had their first stroke between 1995 and 2019 and could be followed for up to 25 years, so many died before a recurrence could be observed, and the competing-risk method allows for those deaths. The estimate also reflects this specific population and era, and earlier cohorts had higher recurrence risks. A person's own stroke type and registered clinical characteristics would shift their individual risk above or below this average.