Dementia risk threefold higher in the first year after a stroke

Stroke survivors were more likely to develop dementia within the first year following their stroke than the general population and people with acute myocardial infarction (MI), according to a study presented at ISC 2024.

“Our findings showed that stroke survivors are uniquely susceptible to dementia, and the risk can be up to three times higher in the first year after a stroke,” said lead author Dr Raed Joundi from McMaster University in Hamilton, Ontario, Canada.

The results were based on a population-wide analysis in Ontario, Canada, between 2002 and 2021, involving 180,940 adults (mean age 69.6 years, 45.5 percent female) who had suffered a recent stroke, either acute ischaemic stroke or intracerebral haemorrhage (ICH), and were free of dementia within 90 days. The stroke survivors group were matched to two control groups, the general population without stroke (99.8 percent) and those with acute MI (90 percent).

After a mean follow-up of 5.5 years (maximum of 20 years), 18.7 percent of stroke survivors were diagnosed with dementia, while only 9 percent had a stroke recurrence.

The stroke survivors demonstrated a higher risk of dementia than the general population (hazard ratio [HR], 1.79), regardless of whether they had an ischaemic stroke (HR, 1.74) or an ICH (HR, 2.43). [ISC 2023, abstract 67]

Compared with those with acute MI, the dementia risk was also higher among stroke survivors (HR, 1.77).

The rate of dementia was higher among stroke survivors cohort vs the general population (3.40 vs 1.88 per 100 person-years) and acute MI cohorts (3.23 vs 1.81 per 100 person-years).

When the analysis was further stratified by age among stroke survivors, a higher risk of dementia was observed in the older cohort aged 65–74, 75–84, and >85 years vs the younger cohort aged 18–44 years (HRs, 2.37, 1.79, and 1.42, respectively, vs 11.34).

Moreover, with regard to sex, the risk of dementia was slightly higher in men than women stroke survivors (HR, 1.96 vs 1.67).

Overall, among stroke survivors, a nearly threefold increase in dementia risk was observed during the first year after a stroke. Although the risk decreased 1.5-fold after 5 years, it remained elevated for up to 20 years.

“Taken together, the risk of dementia was highest in the first year, and highest in younger people,” said Joundi.

Clearly, there is a great burden of dementia after a stroke, Joundi stated.

“We also found that the rate of post-stroke dementia was higher than the rate of recurrent stroke over the same time period,” said Joundi. “Stroke injures the brain including areas critical for cognitive function, which can impact day-to-day functioning. Some people go on to have a recurrent stroke, which increases the risk of dementia even further, and others may experience a progressive cognitive decline similar to a neurodegenerative condition.”

“Our findings reinforce the importance of monitoring people with stroke for cognitive decline, instituting appropriate treatments to address vascular risk factors and prevent recurrent stroke, and encouraging lifestyle changes, such as smoking cessation and increased physical activity, which have many benefits and may reduce the risk of dementia,” noted Joundi.

“More research is needed to clarify why some people with stroke develop dementia and others do not,” he added.