Cognitive impairment better predicts stroke in the very old than Framingham Stroke risk score
Framingham Stroke Risk Score and Cognitive Impairment for Predicting First-Time Stroke in the Oldest Old.
Sabayan B, Gussekloo J, de Ruijter W et al.
Stroke. 2013 May 16. [Epub ahead of print]
BackgroundThe growing number of very old people at high risk for stroke calls for novel strategies for early identification of high risk. Conventional vascular risk factors lose their predictive value for stroke with advancing age [1,2]. It is unclear whether risk prediction models that were constructed based on middle-aged and younger elderly subjects, can accurately identify very old subjects at high risk for stroke .
Cognitive impairment is common in old people and associated with brain vascular pathologies and disturbed cerebrovascular hemodynamics . It has been proposed that impaired cognitive function could be a predictor for first-time stroke in middle-aged and younger elderly people [5,6].
The Framingham stroke risk score has been validated in subjects up to 85 years of age . This study aimed to assess performance of the Framingham stroke risk score and cognitive impairment in predicting 5-year risk of first-time stroke in very old subjects. This observational, prospective, population-based cohort study approached people in the month of their 85th birthday. 480 subjects enrolled. Health information was obtained from the general practitioner and a home visit.
- During 5 years of follow-up, 56 subjects suffered from stroke (30.3 per 1000 person-years).
- Patients who experienced stroke did not have significantly different prevalence of cardiovascular disease, diabetes mellitus, smoking, atrial fibrillation, left ventricular hypertrophy and use of antihypertensive medication, from persons who did not have stroke. Systolic and diastolic blood pressure were also similar between the two groups.
Patients who experienced stroke did have significantly lower Mini-Mental State Examination (MMSE) score at age 85 (median: 24, (IQR: 18-27), vs 27 (24-28), P<0.001).
- A significant difference in cumulative incidence of stroke was seen among subjects with low (17.4, 95%CI: 8.0-26.9), intermediate (27.8, 95%CI: 13.7-41.9) and high (49.5, 95%CI: 31.1-67.8) levels of cognitive impairment. Subjects with more cognitive impairment were at higher risk for stroke as compared with those with low levels of cognitive impairment (HR: 2.85, 95%CI: 1.48-5/51). No such effect was seen for similar categories based on the Framingham risk score.
- MMSE score had discriminative power to predict stroke. A sensitivity analyses that excluded subjects with very low cognitive function, gave similar outcomes. The predictive value of MMSE score for stroke was neither dependent on having had stroke very recently.
ConclusionIn a cohort of individuals of over 85 years old, the Framingham stroke risk score, composed of conventional vascular risk factors, did not predict risk of stroke. Low MMSE scores indicating impaired cognitive function do however identify subjects at higher risk of stroke.
These findings show that when the association between conventional vascular risk factors and cerebrovascular events is weak in the very old, cognitive assessment can be considered as a means to identify subjects at high risk for stroke.
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