Dementia risk increased with greater number, severity of strokes

An increase in incidence or severity of ischaemic strokes was associated with an increased risk of developing dementia, according to the ARIC* study presented at ISC 2021.

“[O]ur results suggest a dose-response relationship between the number of stroke events and stroke severity, and the risk of dementia,” said study author Dr Silvia Koton from the Herczeg Institute on Aging, Tel Aviv University in Tel Aviv, Israel.

Using follow-up data available from three decades of the ARIC database (1987–2019) in the US, the researchers prospectively analysed 15,379 individuals (mean age 54.1 years, 55.2 percent female) with (n=1,156) and without (n=14,223) ischaemic stroke. Stroke severity on admission was classified based on the NIHSS** scores of ≤5, 6–10, 11–15, and ≥16. Incident and recurrent stroke were evaluated based on hospital records. [ISC 2021, abstract 7]

At >30 years of follow-up, dementia occurred more commonly among individuals with than without ischaemic stroke (adjusted hazard ratio [HR], 2.00), with the incidence further increased among those who had ≥3 ischaemic stroke events (adjusted HR, 8.46).

The risk of dementia was stronger among those who experienced severe stroke (NIHSS score ≥16; adjusted HR, 4.74) compared with those without stroke, though the risk was still elevated among those with minor stroke (NIHSS score ≤5; adjusted HR, 1.80).

“The association of stroke occurrence and severity with dementia risk was surprisingly strong, and the continued rise in risk of dementia after the first stroke and each subsequent stroke was a remarkable finding,” said Koton.

The risk of dementia was significantly increased after ischaemic stroke, independent of vascular risk factors, said Koton.

Of note, when the analysis was further stratified by age, participants aged <75 years with stroke demonstrated a higher risk of dementia than those aged >75 years (adjusted HR, 2.43 vs 1.54). “[This finding] emphasizes the importance of preventing stroke to prevent dementia and to maintain high levels of physical and cognitive function and quality of life, especially at older ages,” Koton said.

“Our study uniquely characterizes the link between stroke and dementia and sets the stage for prevention strategies aimed at reducing the risk of dementia after a stroke,” she added.

“[Furthermore], we plan to study the link between stroke and mild cognitive impairment as well as between stroke and changes in cognitive performance over time. Future studies will also include information on brain imaging that will help to evaluate possible effects of vascular brain lesions in addition to stroke,” said Koton.

*ARIC: Atherosclerosis Risk in Communities

**NIHSS: National Institute of Health Stroke Scale