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1.  Atrial fibrillation is associated with reduced brain volume and cognitive function independent of cerebral infarcts 
Background and Purpose
Atrial fibrillation (AF) has been associated with cognitive decline independant of stroke, suggesting additional effects of AF on the brain. We aimed to assess the association between AF and brain function and structure in a general elderly population.
Methods
This is a cross-sectional analysis on 4251 non-demented participants (mean age 76 ± 5 years) in the population-based AGES-Reykjavik Study. Medical record data were collected on the presence, subtype and time from first diagnosis of AF; 330 participants had AF. Brain volume measurements, adjusted for intracranial volume, and presence of cerebral infarcts were determined with MRI. Memory, speed of processing and executive function composites were calculated from a cognitive test battery. In a multivariable linear regression model, adjustments were made for demographic, cardiovascular risk factors and cerebral infarcts.
Results
Participants with AF had lower total brain volume compared to those without AF (p<0.001). The association was stronger with persistent/permanent than paroxysmal AF and with increased time from the first diagnosis of the disease. Of the brain tissue volumes, AF was associated with lower volume of gray and white matter (p<0.001 and p=0.008 respectively) but not of white matter hyperintesities (p=0.49). Participants with AF scored lower on tests on memory.
Conclusions
AF is associated with smaller brain volume and the association is stronger with increasing burden of the arrhythmia. These findings suggest that AF has a cumulative negative effect on the brain independent of cerebral infarcts.
doi:10.1161/STROKEAHA.12.679381
PMCID: PMC3632359  PMID: 23444303
atrial fibrillation; brain imaging; cognition; cerebral infarct
2.  Pulmonary Function Impairment May be An Early Risk Factor for Late-Life Cognitive Impairment 
Background
Low pulmonary function (PF) is associated with poor cognitive function and dementia. There are few studies of change in PF in mid-life and late-life cognitive status.
Design and Participants
We studied this is 3,665 subjects from AGES-Reykjavik Study who had at least one measure of forced expiratory volume/ 1 sec (FEV1) and were cognitively tested on average 23 years later. A subset of 1,281 subjects had two or three measures of FEV1 acquired over a 7.8 year period. PF was estimated as FEV1/Height2. Rate of PF decline was estimated as the slope of decline over time. Cognitive status was measured with continuous scores of memory, speed of processing, and executive function, and as the dichotomous outcomes of mild cognitive impairment (MCI) and dementia.
Results
Lower PF measured in mid-life predicted lower memory, speed of processing, executive function, and higher likelihood of MCI and dementia 23 years later. Decrease of PF over a 7.8-year period in mid-life was not associated with lower cognitive function or dementia.
Conclusion
Reduced PF measured in mid-life may be an early marker of later cognitive problems. Additional studies characterizing early and late PF changes are needed.
doi:10.1111/jgs.12069
PMCID: PMC3545414  PMID: 23311554
Cognition; Dementia; Forced Expiratory Volume; Longitudinal Cohort Studies
3.  Arterial stiffness, pressure and flow pulsatility and brain structure and function: the Age, Gene/Environment Susceptibility – Reykjavik Study 
Brain  2011;134(11):3398-3407.
Aortic stiffness increases with age and vascular risk factor exposure and is associated with increased risk for structural and functional abnormalities in the brain. High ambient flow and low impedance are thought to sensitize the cerebral microcirculation to harmful effects of excessive pressure and flow pulsatility. However, haemodynamic mechanisms contributing to structural brain lesions and cognitive impairment in the presence of high aortic stiffness remain unclear. We hypothesized that disproportionate stiffening of the proximal aorta as compared with the carotid arteries reduces wave reflection at this important interface and thereby facilitates transmission of excessive pulsatile energy into the cerebral microcirculation, leading to microvascular damage and impaired function. To assess this hypothesis, we evaluated carotid pressure and flow, carotid–femoral pulse wave velocity, brain magnetic resonance images and cognitive scores in participants in the community-based Age, Gene/Environment Susceptibility – Reykjavik study who had no history of stroke, transient ischaemic attack or dementia (n = 668, 378 females, 69–93 years of age). Aortic characteristic impedance was assessed in a random subset (n = 422) and the reflection coefficient at the aorta–carotid interface was computed. Carotid flow pulsatility index was negatively related to the aorta–carotid reflection coefficient (R = −0.66, P<0.001). Carotid pulse pressure, pulsatility index and carotid–femoral pulse wave velocity were each associated with increased risk for silent subcortical infarcts (hazard ratios of 1.62–1.71 per standard deviation, P<0.002). Carotid–femoral pulse wave velocity was associated with higher white matter hyperintensity volume (0.108 ± 0.045 SD/SD, P = 0.018). Pulsatility index was associated with lower whole brain (−0.127 ± 0.037 SD/SD, P<0.001), grey matter (−0.079 ± 0.038 SD/SD, P = 0.038) and white matter (−0.128 ± 0.039 SD/SD, P<0.001) volumes. Carotid–femoral pulse wave velocity (−0.095 ± 0.043 SD/SD, P = 0.028) and carotid pulse pressure (−0.114 ± 0.045 SD/SD, P = 0.013) were associated with lower memory scores. Pulsatility index was associated with lower memory scores (−0.165 ± 0.039 SD/SD, P<0.001), slower processing speed (−0.118 ± 0.033 SD/SD, P<0.001) and worse performance on tests assessing executive function (−0.155 ± 0.041 SD/SD, P<0.001). When magnetic resonance imaging measures (grey and white matter volumes, white matter hyperintensity volumes and prevalent subcortical infarcts) were included in cognitive models, haemodynamic associations were attenuated or no longer significant, consistent with the hypothesis that increased aortic stiffness and excessive flow pulsatility damage the microcirculation, leading to quantifiable tissue damage and reduced cognitive performance. Marked stiffening of the aorta is associated with reduced wave reflection at the interface between carotid and aorta, transmission of excessive flow pulsatility into the brain, microvascular structural brain damage and lower scores in various cognitive domains.
doi:10.1093/brain/awr253
PMCID: PMC3212721  PMID: 22075523
haemodynamics; aortic stiffness; magnetic resonance imaging; brain structure; cognitive function
4.  Coronary Artery Calcium, Brain function and structure: the AGES-Reykjavik Study 
Background and Purpose
Several cardiovascular risk factors are associated with cognitive disorders in older persons. Little is known about the association of the burden of coronary atherosclerosis with brain structure and function.
Methods
Cross-sectional analysis of data from the AGES Reykjavik Study cohort of men and women born 1907-35. Coronary artery calcification (CAC), a marker of atherosclerotic burden was measured with computed tomography. Memory, speed of processing, and executive function composites were calculated from a cognitive test battery. Dementia was assessed in a multi-step procedure and diagnosed according to international guidelines. Quantitative data on total intracranial and tissue volumes [total, Gray (GMV), White (WMV), and White Matter Lesions (WMLV)], cerebral infarcts and cerebral microbleeds (CMB) were obtained with brain MRI. The association of CAC with dementia (n=165 cases) and cognitive function in non-demented subjects (n=4085), and separately with MRI outcomes, was examined in multivariate models adjusting for demographic and vascular risk factors. Analyses tested whether brain structure mediated the associations of CAC to cognitive function.
Results
Subjects with higher CAC were more likely to have dementia and lower cognitive scores, more likely to have lower WMV, GMV and total brain tissue, and more cerebral infarcts, CMB and WMLV. The relations of cognitive performance and dementia to CAC were significantly attenuated when the models were adjusted for brain lesions and volumes.
Conclusions
In a population-based sample increasing atherosclerotic load, assessed by CAC, is associated with poorer cognitive performance and dementia, and these relations are mediated by evidence of brain pathology.
doi:10.1161/STROKEAHA.110.579581
PMCID: PMC3298743  PMID: 20360538
Atherosclerosis; Coronary Artery Disease; Calcinosis/radiography; Dementia; Cognitive function
5.  Cerebral infarcts and cognitive performance: Importance of location and number of infarcts. The Age, Gene/Environment Susceptibility – Reykjavik Study 
Background & Purpose
Cerebral infarcts increase the risk for cognitive impairment. The relevance of location and number of infarcts with respect to cognitive function is less clear.
Methods
We studied the cross-sectional association between number and location of infarcts and cognitive performance in 4030 non-demented participants of the Age Gene/Environment Susceptibility-Reykjavik Study. Composite scores for memory (MEM), processing speed (SP) and executive function (EF) were created from a neuropsychological battery. Subcortical, cortical, and cerebellar infarcts were identified on brain MRI. We performed linear-regression analyses adjusted for demographic and vascular risk factors, depression, white matter lesions, and atrophy.
Results
Compared to participants with no infarcts, those with infarcts in multiple locations (n=287, 7%) had slower SP (β=-0.19, p<.001) and poorer MEM (β=-0.16, p<.001) and EF (β=-0.12, p=.003). Compared to no infarcts, the presence of either subcortical infarcts only (n=275) (β=-0.12, p=.016) or cortical infarcts only (n=215) (β=-0.17, p=.001) was associated with poorer MEM performance. Compared to no infarcts, a combination of cortical and subcortical infarcts (n=45) was associated with slower SP (β=-0.38, p<.001) and poorer EF (β=-0.22, p=.02), while a combination of cerebellar and subcortical infarcts (n=89) was associated with slower SP (β=-0.15, p=.04). Infarcts in all three locations was associated with slower SP (β=-0.33, p=.002).
Conclusions
Having infarcts in more than one location is associated with poor performance in memory, processing speed, and executive function, independent of cardiovascular comorbidities, white matter lesions and brain atrophy, suggesting that both the number and the distribution of infarcts jointly contribute to cognitive impairment.
doi:10.1161/STROKEAHA.108.530212
PMCID: PMC3244834  PMID: 19131654
6.  The Effect of Midlife Physical Activity on Cognitive Function Among Older Adults: AGES—Reykjavik Study 
Background.
There are few studies on the long-term associations of physical activity (PA) to cognition. Here, we examine the association of midlife PA to late-life cognitive function and dementia.
Methods.
The sample consisted of a population-based cohort of men and women (born in 1907–1935) participating in the Age Gene/Environment Susceptibility—Reykjavik Study. The interval between the midlife ascertainment of PA and late-life cognitive function was 26 years. Composite scores of speed of processing, memory, and executive function were assessed with a battery of neuropsychological tests, and dementia was diagnosed according to international guidelines. There were 4,761 nondemented participants and 184 (3.7%) with a diagnosis of dementia, with complete data for the analysis.
Results.
Among the participants, no midlife PA was reported by 68.8%, ≤5 hours PA by 26.5%, and >5 hours PA by 4.5%. Excluding participants with dementia compared with the no PA group, both PA groups had significantly faster speed of processing (≤5 hours, β = .22; >5 hours, β = .32, p trend < .0001), better memory (≤5 hours, β = .15; >5 hours, β = .18, p trend < .0001), and executive function (≤5 hours, β = .09; >5 hours, β = .18, p trend< .0001), after controlling for demographic and cardiovascular factors. The ≤5 hours PA group was significantly less likely to have dementia in late life (odds ratio: 0.6, 95% confidence interval: 0.40–0.88) after adjusting for confounders.
Conclusion.
Midlife PA may contribute to maintenance of cognitive function and may reduce or delay the risk of late-life dementia.
doi:10.1093/gerona/glq152
PMCID: PMC2990266  PMID: 20805238
Physical activity; Cognitive function; Longitudinal study

Results 1-6 (6)