Adult stroke survivors are nearly twice as likely to have dementia as adults who have not had a stroke, new research suggests.
The study also found that suffering two or more moderate to severe strokes increased the risk of dementia by almost seven times.
The findings from the study are published in the journal, JAMA Neurology.
Lead author Silvia Koton, PhD, a stroke epidemiologist and head of the Herczeg Institute on Aging at Tel Aviv University, said:
“The strength of the association between stroke occurrence, stroke severity, and risk of dementia is impressive.
“Our findings emphasise the value of both primary and secondary stroke prevention for reducing dementia risk and [for] achieving high levels of function and quality of life, especially at older ages.”
The researchers analysed the associations between dementia and ischemic stroke incidence, frequency and severity in 15,379 individuals.
The participants were enrolled in a US atherosclerosis study. The condition causes a thickening or hardening of the arteries.
None of the participants had a history of stroke and dementia at the start of the study at baseline between 1987 and 1989.
The participants were monitored throughout 2019, with an average of 4.4 visits and follow-up calls conducted annually until 2021 and every six months since 2012.
A total of 73.3 per cent of patients were white, the mean age was 54.1 years and 55.2 per cent were women.
A total of 1,378 ischemic strokes and 2,860 cases of dementia occurred over a median follow-up of 25.5 years.
Dementia cases occurring within a year after a first stroke were not included.
The research revealed that 62.8 per cent of 1,184 strokes were minor, 21.1 per cent were mild, 7.9 percent were moderate and 7.1 per cent were severe.
The proportion of dementia risk attributed to stroke was 17.4 per cent and increased with the frequency of stroke, from 9.1 per cent for one stroke to 53 per cent for more than two strokes, as well as by severity of stroke from 7 percent for minor stroke to 50 percent for severe stroke.
The researchers found increased hazard rates of dementia associated with stroke severity and frequency after adjusting for demographic and vascular risk factors.
Compared with no stroke, the dementia risk was 1.73 higher for one minor to mild stroke and nearly seven times higher for two or more moderate to severe strokes.
According to the researchers, the findings suggest that:
“Either (1) risk-factor control is worse in individuals with one or several (or more severe) strokes, which is associated with increases in dementia risk; (2) an ongoing unaccounted for process or confounder may lead to elevated stroke risk as well as risk of dementia; or (3) stroke has a long-term impact on cognition leading to dementia via unmeasured or subclinical ischemic injury.”
Nneka L. Ifejika, MD, MPH, associate professor of neurology and section chief of stroke rehabilitation at UT Southwestern Medical Center, added:
“It is imperative that we take a proactive approach in stroke awareness and risk factor management.”
