An analysis of data from a stroke registry compiled in Spain indicates that patients who have post-stroke dementia have a more than eight-fold increase in risk of death within two years of stroke than patients who have no signs of dementia after stroke. When dementia was diagnosed before the stroke, the risk for death was twice as high as the death risk for patients who had no dementia before or after stroke. When dementia is related to stroke, the risk for death within two years increased more than six-fold.
Researchers found that dementia - declines in memory, cognitive function and capacity to perform daily living activities - is an independent risk factor for death after stroke and one of the most important determinants of death in stroke patients, explains the study's lead author Raquel Barba, M.D., Ph.D., a clinical investigator in the department of medicine at Fundación Hospital Alcorcón, Madrid, Spain.
A possible explanation for the poor survival rate among stroke survivors with dementia is that these patients may not receive the same treatment as stroke survivors who have no cognitive impairment, says Barba. For example, the study found that a patient with dementia was less likely to be treated with oral anticoagulants than one without dementia, even if atrial fibrillation was diagnosed. Atrial fibrillation is an abnormal heart rhythm associated with increased risk for blood clots. It's often treated with anticoagulants to prevent stroke. But these drugs require careful compliance with dosing guidelines and patients with dementia are less likely to comply with medication regimens.
Patients with dementia did receive the same antihypertensive medications and antiaggregant treatments as stroke patients without dementia. But, after discharge from the hospital, dementia patients were less likely to have their blood sugar levels closely monitored, which is recommended to prevent complications associated with diabetes.
Currently, stroke prevention focuses on patients without dementia, but based on the study, Barba believes antiplatelet therapy, blood sugar control and blood pressure control are important keys even in patients with dementia. For patients who have pre-existing dementia, stroke likely worsens the dementia resulting in poor functional, neurologic and vital prognosis, so preventing stroke is also important in these patients, she says.
The stroke registry included data from 324 patients admitted to a Madrid hospital for stroke treatment between May 1, 1994, and September 30, 1995. When the patients were admitted a close relative or caregiver completed a detailed questionnaire on cognitive decline called the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Information from that questionnaire, as well as medical history and neurological evaluation, identified pre-stroke dementia in 49 patients.
Three months after the stroke neurological evaluation, another IQCODE and a mental status questionnaire identified 75 cases of post-stroke dementia, including 50 cases in which the dementia was stroke-related.
After adjusting for other known risk factors for stroke-related mortality - age, gender, high blood pressure, diabetes, history of previous stroke, heart disease and severity of stroke - dementia remained a predictor of stroke mortality, says Barba. After correcting for the other risk factors, the relative risk of mortality for patients with pre-stroke dementia was 2.1. It was 6.4 for those with stroke-related dementia and 8.5 for those who with post-stroke dementia.
After nearly two years of follow-up, 58.3 percent of patients with stroke-related dementia survived compared to 95.4 percent of patients without it.
Dementia is commonly associated with Alzheimer's disease, but another type of dementia is caused by narrowing of the blood vessels inside the brain. This narrowing reduces the supply of blood that carries oxygen and nutrients to keep brain cells alive and functioning. This type of dementia is called vascular dementia and has been associated with stroke. In this study, 63 of the 75 patients with post-stroke dementia had vascular dementia, while 12 had "degenerative dementia plus stroke," says Barba.
Also in the August issue of Stroke, a team of Canadian researchers report that administering a battery of neuropsychological tests can help physicians predict which patients who have slight cognitive impairment caused by vascular disease will lead to dementia. A third study, by researchers from Texas, also suggests that mild cognitive impairment may predict vascular dementia in much the same way that neurologists consider it to be a precursor for Alzheimer's disease.
Barba's co-authors are Maria-del-Mar Morin, M.D.; Carlos Cemillán, M.D.; Carlos Delgado, Ph.D.; Julio Domingo, M.D.; and Teodoro Del Ser, M.D., Ph.D. The research was partly funded by Bayer S.A.
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