Hypertension in Midlife Linked to Risk of Dementia in Later Life
In addition to being cardiovascular risk factors, hypertension, hypercholesterolemia, diabetes, and smoking in middle age may significantly increase the risk of dementia in later life, according to the results of a study by California researchers published in the January issue of Neurology , the scientific journal of the American Academy of Neurology. Previous studies have associated individual cardiovascular risk factors with a higher risk of dementia, but this is the first time that the association of these risk factors in midlife with risk of dementia in older age has been investigated, the researchers believe.
Rachel A. Whitmer, MD (Kaiser Permanente Division of Research, Oakland, California), and co-investigators conducted a retrospective cohort study of 8845 participants who underwent health evaluations between 1964 and 1973 in Oakland and San Francisco. All participants were aged between 40 and 44 years at the time of their evaluation. Between January 1, 1994, and April 3, 2003, 721 participants (8.2%) were diagnosed with dementia. Mean age at diagnosis was 74.5 years.
All of the cardiovascular risk factors of midlife were significantly associated with a 20% to 40% increased risk of dementia in late life. Those with hypertension (self-report of physician diagnosis, SBP ≥ 140 mm Hg or DBP ≥ 90 mm Hg, or use of antihypertensive medication) were 24% more likely to have dementia. Increased risks were also associated with diabetes (46%), hypercholesterolemia (42%), and smoking (26%).
The composite cardiovascular disease risk score, based on a modified version of the Framingham Cardiovascular Risk Score and incorporating all 4 risk factors in midlife, showed a dose-dependent relationship with risk of late-life dementia. Compared with the absence of any cardiovascular risk factors, having 1 cardiovascular risk factor was associated with a 27% increased risk of being diagnosed with dementia. The presence of 3 or all 4 risk factors increased the risk by more than 2-fold.
Treatment of hypertension in late life has been shown to reduce cognitive impairment and the risk of dementia, and Dr. Whitmer and colleagues advocate further studies to determine whether treating the other risk factors for heart disease may also reduce the risk for dementia. Earlier treatment may have an even greater benefit by virtue of the cumulative effect of longer exposure to protective therapies, they note. They also call for studies to elucidate the mechanisms involved in earlier prevention.
In a separate paper published in the same issue of Neurology , researchers from The Netherlands report that blood pressure, as well as indicators of small vessel disease in the brain, may correlate with atrophy of structures affected by Alzheimer's disease. A magnetic resonance imaging (MRI) study in 511 nondemented elderly subjects showed that those with high DBP but untreated for hypertension had more hippocampal atrophy on MRI 5 years later. However, and apparently anomalously, in those using antihypertensive medications, a low DBP was associated with more hippocampal and amygdalar atrophy. The presence of white matter lesions, a marker of small vessel disease, on MRI also correlated with the presence of Alzheimer's disease.
Monique MB Breteler, MD, PhD (Erasmus Medical Center, Rotterdam, The Netherlands), and colleagues believe that their results are consistent with those of previously reported studies showing that high blood pressure is a risk factor for cognitive impairment and clinical Alzheimer's disease. To explain the latter observation, they noted that shortly before or at the time of diagnosis of Alzheimer's disease, patients have been reported as having lower blood pressure levels than controls. Further study to explain these processes is clearly warranted, but in the meantime, high DBP in elderly persons may be seen as a possible indicator of risk for Alzheimer's disease.
Medscape Cardiology. 2005;9(1) © 2005 Medscape
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