Cardiovascular diseases, health status, brain imaging findings and neuropsychological functioning in neurologically healthy elderly individuals
Introduction
There are many aspects of medical, biological and social-demographic domains that can be associated with, or even causal to, declining cognitive functions in the elderly. One of the most frequently studied aspects has been general health status (Benton and Sivan, 1984, Perlmutter and Nyquist, 1990, Christensen et al., 1994, Earles and Salthouse, 1995, Emery et al., 1995). Although it is assumed that poor health contributes to accelerated decline in intellectual functioning (Benton and Sivan, 1984) the results are still contradictory. Especially self-rated health status does not explain cognitive decline in some studies (Christensen et al., 1994, Earles and Salthouse, 1995). However, many studies show a significant relationship between health status and cognitive decline (Perlmutter and Nyquist, 1990, Emery et al., 1995). Neurological diseases, like dementing disorders, can cause severe alterations in cognition. In differentiating other medical conditions influencing cognitive abilities the role of cardiovascular diseases has been emphasized (Hertzog et al., 1978).
Cardiovascular diseases are essential for their possible connection to brain pathology (Shimada et al., 1990). Many studies have discovered a relationship between hypertension or high blood pressure and cognitive deficits (Parnetti et al., 1989, Elias et al., 1990, Elias et al., 1993, Elias et al., 1996). However, some studies have found no association between cognitive performance and blood pressure among subjects on drug therapy for hypertension (Farmer et al., 1990, Goldstein et al., 1990). There is evidence that those hypertensive subjects who have shown extensive white matter lesions have also exhibited impairment of attention (Schmidt et al., 1995) and visual memory (Van Swieten et al., 1991), or executive functioning (DeCarli et al., 1995).
Atherosclerotic diseases have been found to account for a considerable cognitive impairment in the general population including subjects with stroke (Breteler et al., 1994). The type and mechanisms of cognitive difficulties in neurologically healthy subjects with cardiovascular diseases is less studied, although even 40% of cardiac patients have exhibited clear difficulties in cognitive functions and 30% mild difficulties (Barclay et al., 1988). Cardiovascular diseases or risk factors have been related to poorer memory performance and attention (Farina et al., 1997, Vingerhoets et al., 1997), or to abstraction and visuospatial functions (Desmond et al., 1993), or to lower cognitive status (Kilander et al., 1998). Likewise patients with peripheral vascular disease have demonstrated cognitive deficits (Phillips and Mate-Kole, 1997). Little is known about the morphological basis of the cognitive difficulties in neurologically healthy cardiac patients. Schmidt et al. (1991) found that in the middle aged patients with cardiomyopathy, cognitive test performance was significantly worse in patients with ventricular enlargement and cortical atrophy.
The purpose of our study was to evaluate the relationship of health-related factors in relation to brain imaging variables with cognitive functioning in a neurologically healthy, community-dwelling, elderly population sample. The main issue was to study whether cardiovascular diseases would be related to brain changes and if in combination they would be associated with specific cognitive difficulties. In addition, we studied whether health status or presence of systemic diseases or depression score would influence cognitive functions.
Section snippets
Subjects
In the Helsinki Aging Brain Study in an unselected sample of individuals living at home were invited from age cohorts of 55, 60, 65, 70, 75, 80 and 85 years of age. These cohorts included 40, 43, 37, 53, 52, 63, and 50 persons, respectively. From this sample of 338 individuals 50 refused to participate, 13 died and seven moved away. A neurologist (AY) clinically examined all the remaining 268 subjects (Ylikoski et al., 1995). From these 37 (13.8%) had conditions affecting the central nervous
Results
The age cohorts were combined into three age groups, aged 55 and 60 years together, aged 65 and 70 together, and aged 75, 80, 85 together (Table 1). The number of years of education was quite small in this sample. Most of them had only gone to grade school. This unselected, home-dwelling sample consisted of subjects who were relatively healthy (Table 1), although physicians’ rating of health status deteriorated and frequency of systemic diseases increased with age. Approximately half of the
Discussion
We examined a population based, unselected sample of individuals living at home. Detailed neurological examinations were performed to exclude cases with neurological diseases. Due to the extensive battery of investigations the sample size remained relatively small. We singled out six clinically and neuropsychologically essential cognitive domains; verbal memory, visual memory, verbal intellectual functions, visuoconstructional and spatial functions, mental flexibility, as well as speed and
Acknowledgements
This study was supported in part by grants from the Kordelin Foundation, Helsinki, the Finnish Alzheimer Foundation for Research, Helsinki, and the Clinical Research Institute, Helsinki University Hospital, Helsinki. We would like to thank Pekka Karhunen, MD, PhD, from the Internal Faculty of Medicine, University of Tampere, for analysing the APOE results. We would also like to thank Dr Mark Shackleton from the University of Helsinki for revising the English language of the text.
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