Age, Vascular Risk, and Cognitive Decline in an Older, British, African-Caribbean Population

Physical Activity and Cognitive Decline Among Older Adults: A Systematic Review and Meta-Analysis

Importance

Physical activity is associated with the risk for cognitive decline, but much of the evidence in this domain comes from studies with short follow-ups, which is prone to reverse causation bias.

Objective

To examine how length of follow-up, baseline age, physical activity amount, and study quality modify the longitudinal associations of physical activity with cognition.

Data Sources

Observational studies of adults with a prospective follow-up of at least 1 year, a valid baseline cognitive measure or midlife cohort, and an estimate of the association of baseline physical activity and follow-up cognition were sought from PsycInfo, Scopus, CINAHL, Web of Science, SPORTDiscus, and PubMed, with the final search conducted on November 2, 2022.

Study Selection

Two independent researchers screened titles with abstracts and full-text reports.

Data Extraction and Synthesis

Two reviewers independently assessed study quality and extracted data. Pooled estimates of association were calculated with random-effects meta-analyses. An extensive set of moderators, funnel plots, and scatter plots of physical activity amount were examined. This study is reported following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

Main Outcomes and Measures

Pooled estimates of the associations between physical activity and global cognition, as well as specific cognitive domains, were examined.

Results

A total of 104 studies with 341 471 participants were assessed. Analysis of binary outcomes included 45 studies with 102 452 individuals, analysis of follow-up global cognition included 14 studies with 41 045 individuals, and analysis of change in global cognition included 25 studies with 67 463 individuals. Physical activity was associated with a decreased incidence of cognitive impairment or decline after correction for funnel plot asymmetry (pooled risk ratio, 0.97; 95% CI, 0.97-0.99), but there was no significant association in follow-ups longer than 10 years. Physical activity was associated with follow-up global cognition (standardized regression coefficient, 0.03; 95% CI, 0.02-0.03) and change in global cognition (standardized regression coefficient, 0.01; 95% CI, 0.01 to 0.02) from trim-and-fill analyses, with no clear dose-response or moderation by follow-up length, baseline age, study quality or adjustment for baseline cognition. The specific cognitive domains associated with physical activity were episodic memory (standardized regression coefficient, 0.03; 95% CI, 0.02-0.04) and verbal fluency (standardized regression coefficient, 0.05; 95% CI, 0.03-0.08).

Conclusions and Relevance

In this meta-analysis of the association of physical activity with cognitive decline, physical activity was associated with better late-life cognition, but the association was weak. However, even a weak association is important from a population health perspective.

Prevalence and incidence of mild cognitive impairment in adults with diabetes in the United States

BACKGROUND

Limited evidence exists about the prevalence and incidence of mild cognitive impairment (MCI) in individuals with diabetes in the U.S. We aimed to address such knowledge gaps using a nationally representative study dataset.

METHOD

We conducted a secondary analysis from the Health and Retirement Study (HRS) (1996-2018). The sample for examining the prevalence of MCI was14,988, with 4192 (28.0%) having diabetes, while the sample for the incidence was 21,824, with 1534 (28.0%) having diabetes.

RESULTS

Participants with diabetes had a higher prevalence of MCI than those without diabetes (19.9 % vs. 14.8 %; odds ratio [95 % confidence interval] (OR[95 %CI]): 1.468 [1.337, 1.611], p <.001). The incidence of MCI in participants with/without newly diagnosed diabetes was 42.9 % vs. 31.6 % after a mean 10-year follow-up, with the incidence rate ratio (IRR) [95 %CI] (1.314 [1.213, 1.424], p <.001). Newly diagnosed diabetes was associated with elevated risks of MCI compared with non-diabetes, with the uncontrolled hazard ratio (HR) [95 %CI] (1.498 [1.405, 1.597], p <.001).

CONCLUSIONS

Using a nationally representative study data in the U.S., participants with diabetes had a higher prevalence and incidence of MCI than those without diabetes. Findings show the importance of developing interventions tailored to the needs of individuals with diabetes and cognitive impairment.

Patterns and risk factors of cognitive decline among community-dwelling older adults in South Korea

Dementia prevalence is increasing worldwide. Thus, the global impact of cognitive impairment and dementia have become significant public health issues. This study assessed the patterns of and investigated risk factors associated with cognitive decline over time in community-dwelling Korean adults (age ≥65 years). We enrolled 1,369 older adult respondents without cognitive decline in the baseline survey of the Korean Longitudinal Study of Aging (2006-2016) in South Korea. The risk of first-ever mild-to-moderate or severe cognitive decline during the 10-year follow-up (2006-2016) was comparatively evaluated between the cognitive decline group (comprising participants with mild-to-moderate or severe cognitive decline; n = 728) and the normal cognition group (participants without a cognitive decline event; n = 641). The cognitive decline-free survival rates for up to ten years were measured using Kaplan-Meier analysis. The generalized estimation equations model was used to analyze changes in K-MMSE over time from 2006 to 2016. The adjusted Cox proportional hazards model revealed that increased age, female, lower education level, no religious status, and living in a small city were factors that were associated with a higher risk of cognitive decline, as were health-related factors, including lower handgrip strength, a higher number of chronic diseases, and depressive symptoms. Regular exercise, non-drinking status, and active social engagements reduced the risk of cognitive decline. The identified risk factors could facilitate the development of cognitive decline-prevention programs incorporating individualized risk-modification interventions to prevent cognitive decline in older adults.

Relationship between Arterial Hypertension with Cognitive Performance in Elderly. Systematic Review and Meta-Analysis

Background: Previous systematic reviews report that arterial hypertension (AHT) is associated with lower performance in cognition in the elderly. However, some studies show that with higher blood pressure, a better cognitive performance is obtained. Objective: The aim of this study was to determine the relationship between AHT with cognitive performance in the elderly. Methods: the review involved a search on PubMed, Scopus and PsycINFO databases from January 1990 to March, 2020 to identify the relationship among AHT and cognitive performance in older people. Results: 1170 articles were identified, 136 complete papers were reviewed, a qualitative analysis of 26 studies and a quantitative analysis of eight studies were carried out. It was found that people with AHT have a lower performance in processing speed SMD = 0.40 (95% CI: 0.25, 0.54), working memory SMD = 0.28 (95% CI: 0.15, 0.41) in short-term memory and learning SMD = −0.27 (95% CI: −0.37, −0.17) and delayed recall SMD = −0.20 (95% CI: −0.35, −0.05). Only one study found that higher blood pressure was associated with better memory performance. Conclusion: Our results suggest that high blood pressure primarily affects processing speed, working memory, short-term memory and learning and delayed recall.

Olfactory dysfunction predicts the development of dementia in older patients with type 2 diabetes

AIMS

Olfactory dysfunction is associated with the transition from normal cognition to dementia in persons without type 2 diabetes. This study aimed to investigate whether olfactory dysfunction could be an early marker of future dementia in older patients with type 2 diabetes.

METHODS

This exploratory study included 151 older Japanese outpatients with type 2 diabetes who did not have a diagnosis of probable dementia at baseline. A multivariate logistic regression model was used to determine whether Open Essence (OE) test score at baseline is associated with the development of probable dementia.

RESULTS

Over 3 years, approximately 9% of the study subjects developed probable dementia. Subjects with olfactory dysfunction at baseline developed probable dementia more frequently than those without. Multivariate logistic regression showed that lower OE test score, higher age, lower Mini-Mental State Examination (MMSE) score, higher total protein concentration, and more frequent use of a sulfonylurea are significantly associated with the development of probable dementia. Stepwise multivariate regression analysis demonstrated that change in OE test score over 3 years is significantly associated with change in MMSE score.

CONCLUSIONS

Our study suggested that olfactory dysfunction precedes the development of probable dementia in older patients with type 2 diabetes.

Cerebral Blood Flow and Cognitive Functioning in a Community-Based, Multi-Ethnic Cohort: The SABRE Study

Introduction: Lower cerebral blood flow (CBF) is associated with cardiovascular disease and vascular risk factors, and is increasingly acknowledged as an important contributor to cognitive decline and dementia. In this cross-sectional study, we examined the association between CBF and cognitive functioning in a community-based, multi-ethnic cohort. Methods: From the SABRE (Southall and Brent Revisited) study, we included 214 European, 151 South Asian and 87 African Caribbean participants (71 ± 5 years; 39%F). We used 3T pseudo-continuous arterial spin labeling to estimate whole-brain, hematocrit corrected CBF. We measured global cognition and three cognitive domains (memory, executive functioning/attention and language) with a neuropsychological test battery. Associations were investigated using linear regression analyses, adjusted for demographic variables, vascular risk factors and MRI measures. Results: Across groups, we found an association between higher CBF and better performance on executive functioning/attention (standardized ß [stß] = 0.11, p < 0.05). Stratification for ethnicity showed associations between higher CBF and better performance on memory and executive functioning/attention in the white European group (stß = 0.14; p < 0.05 and stß = 0.18; p < 0.01 respectively), associations were weaker in the South Asian and African Caribbean groups. Conclusions: In a multi-ethnic community-based cohort we showed modest associations between CBF and cognitive functioning. In particular, we found an association between higher CBF and better performance on executive functioning/attention and memory in the white European group. The observations are consistent with the proposed role of cerebral hemodynamics in cognitive decline.

Associations Between Left Ventricular Dysfunction and Brain Structure and Function: Findings From the SABRE (Southall and Brent Revisited) Study

Background

Subclinical left ventricular (LV) dysfunction has been inconsistently associated with early cognitive impairment, and mechanistic pathways have been poorly considered. We investigated the cross‐sectional relationship between LV dysfunction and structural/functional measures of the brain and explored the role of potential mechanisms.

Method and Results

A total of 1338 individuals (69±6 years) from the Southall and Brent Revisited study underwent echocardiography for systolic (tissue Doppler imaging peak systolic wave) and diastolic (left atrial diameter) assessment. Cognitive function was assessed and total and hippocampal brain volumes were measured by magnetic resonance imaging. Global LV function was assessed by circulating N‐terminal pro–brain natriuretic peptide. The role of potential mechanistic pathways of arterial stiffness, atherosclerosis, microvascular disease, and inflammation were explored. After adjusting for age, sex, and ethnicity, lower systolic function was associated with lower total brain (beta±standard error, 14.9±3.2 cm³; P<0.0001) and hippocampal volumes (0.05±0.02 cm³, P=0.01). Reduced diastolic function was associated with poorer working memory (−0.21±0.07, P=0.004) and fluency scores (−0.18±0.08, P=0.02). Reduced global LV function was associated with smaller hippocampal volume (−0.10±0.03 cm³, P=0.004) and adverse visual memory (−0.076±0.03, P=0.02) and processing speed (0.063±0.02, P=0.006) scores. Separate adjustment for concomitant cardiovascular risk factors attenuated associations with hippocampal volume and fluency only. Further adjustment for the alternative pathways of microvascular disease or arterial stiffness attenuated the relationship between global LV function and visual memory.

Conclusions

In a community‐based sample of older people, measures of LV function were associated with structural/functional measures of the brain. These associations were not wholly explained by concomitant risk factors or potential mechanistic pathways.

Aerobic Exercise as a Tool to Improve Hippocampal Plasticity and Function in Humans: Practical Implications for Mental Health Treatment

Aerobic exercise (AE) has been widely praised for its potential benefits to cognition and overall brain and mental health. In particular, AE has a potent impact on promoting the function of the hippocampus and stimulating neuroplasticity. As the evidence-base rapidly builds, and given most of the supporting work can be readily translated from animal models to humans, the potential for AE to be applied as a therapeutic or adjunctive intervention for a range of human conditions appears ever more promising. Notably, many psychiatric and neurological disorders have been associated with hippocampal dysfunction, which may underlie the expression of certain symptoms common to these disorders, including (aspects of) cognitive dysfunction. Augmenting existing treatment approaches using AE based interventions may promote hippocampal function and alleviate cognitive deficits in various psychiatric disorders that currently remain untreated. Incorporating non-pharmacological interventions into clinical treatment may also have a number of other benefits to patient well being, such as limiting the risk of adverse side effects. This review incorporates both animal and human literature to comprehensively detail how AE is associated with cognitive enhancements and stimulates a cascade of neuroplastic mechanisms that support improvements in hippocampal functioning. Using the examples of schizophrenia and major depressive disorder, the utility and implementation of an AE intervention to the clinical domain will be proposed, aimed to reduce cognitive deficits in these, and related disorders.

Incidental Intracranial Findings and Their Clinical Impact; The HUNT MRI Study in a General Population of 1006 Participants between 50-66 Years

OBJECTIVES

Evaluate types and prevalence of all, incidental, and clinically relevant incidental intracranial findings, i.e. those referred to primary physician or clinical specialist, in a cohort between 50 and 66 years from the Nord-Trøndelag Health (HUNT) study. Types of follow-up, outcome of repeated neuroimaging and neurosurgical treatment were assessed.

MATERIAL AND METHODS

1006 participants (530 women) underwent MRI of the head at 1.5T consisting of T1 weighted sagittal IR-FSPGR volume, axial T2 weighted, gradient echo T2* weighted and FLAIR sequences plus time of flight cerebral angiography covering the circle of Willis. The nature of a finding and if it was incidental were determined from previous radiological examinations, patient records, phone interview, and/or additional neuroimaging. Handling and outcome of the clinically relevant incidental findings were prospectively recorded. True and false positives were estimated from the repeated neuroimaging.

RESULTS

Prevalence of any intracranial finding was 32.7%. Incidental intracranial findings were present in 27.1% and clinically relevant findings in 15.1% of the participants in the HUNT MRI cohort. 185 individuals (18.4%) were contacted by phone about their findings. 40 participants (6.2%) underwent ≥ 1 additional neuroimaging session to establish etiology. Most false positives were linked to an initial diagnosis of suspected glioma, and overall positive predictive value of initial MRI was 0.90 across different diagnoses. 90.8% of the clinically relevant incidental findings were developmental and acquired cerebrovascular pathologies, the remaining 9.2% were intracranial tumors, of which extra-axial tumors predominated. In total, 3.9% of the participants were referred to a clinical specialist, and 11.7% to their primary physician. 1.4% underwent neurosurgery/radiotherapy, and 1 (0.1%) experienced a procedure related postoperative deficit.

CONCLUSIONS

In a general population between 50 and 66 years most intracranial findings on MRI were incidental, and >15% of the cohort was referred to clinical-follow up. Hence good routines for handling of findings need to be in place to ensure timely and appropriate handling.

The relationship between diabetic retinopathy and cognitive impairment

OBJECTIVE

Recent studies have shown an increased risk for cognitive impairment and dementia in patients with diabetes. An association between diabetic retinopathy (DR) and retinal microvasculature disease and cognitive impairment has been reported as potential evidence for a microvascular component to the cognitive impairment. It was hypothesized that severity of DR would be associated with cognitive impairment in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Three hundred eighty patients with type 2 diabetes were recruited from a population-based eye screening program and grouped by severity of DR as follows: no/mild DR (n=252) and proliferative diabetic retinopathy (PDR) (n=128). Each participant underwent psychosocial assessment; depression screening; ophthalmic and physical examination, including blood assays; and cognitive assessment with the Addenbrooke's Cognitive Examination-Revised (ACE-R), Mini-Mental State Examination (MMSE), and the Mini-Cog. General linear modeling was used to examine severity of DR and cognitive impairment, adjusting for confounders.

RESULTS

Severity of DR demonstrated an inverse relationship with cognitive impairment (fully adjusted R2=0.415, P<0.001). Ethnicity contributed most to the variance observed (16%) followed by education (7.3%) and retinopathy status (6.8%). The no/mild DR group had lower cognitive impairment scores on ACE-R (adjusted mean±SE 77.0±1.9) compared with the PDR group (82.5±2.2, P<0.001). The MMSE cutoff scores showed that 12% of the no/mild DR group (n=31) had positive screening results for dementia or significant cognitive impairment compared with 5% in the PDR group (n=6).

CONCLUSIONS

Patients with minimal DR demonstrated more cognitive impairment than those with advanced DR. Therefore, the increased prevalence of cognitive impairment in diabetes may be associated with factors other than evident retinal microvascular disease.

Impact of aerobic exercise on neurobehavioral outcomes

Numerous studies have examined the relationship between physical activity and cognitive function, demonstrating that greater physical activity is associated with lower incidence of cognitive impairment in later life. Due to an increasingly large number of older adults at risk for cognitive impairment, the relationship between physical activity and cognition has garnered increasing public health relevance and multiple randomized trials have demonstrated that exercise interventions among sedentary adults improve cognitive performance in multiple domains of function. This article will examine the relationship between physical activity and cognitive function by reviewing several different areas of literature, including the prevalence of cognitive impairment, assessment methods, observational studies examining physical activity and cognition, and intervention studies. The present review is intended to provide a historical tutorial of existing literature linking physical activity, exercise, and cognitive function among both healthy and clinical populations.

Depressive symptoms, chronic diseases, and physical disabilities as predictors of cognitive functioning trajectories in older Americans

OBJECTIVES

To determine the concurrent influence of depressive symptoms, medical conditions, and disabilities in activities of daily living (ADLs) on rates of decline in cognitive function of older Americans.

DESIGN

Prospective cohort.

SETTING

National population based.

PARTICIPANTS

A national sample of 6,476 adults born before 1924.

MEASUREMENTS

Differences in cognitive function trajectories were determined according to prevalence and incidence of depressive symptoms, chronic diseases, and ADL disabilities. Cognitive performance was tested five times between 1993 and 2002 using a multifaceted inventory examined as a global measure (range 0-35, standard deviation (SD) 6.0) and word recall (range 0-20, SD 3.8) analyzed separately.

RESULTS

Baseline prevalence of depressive symptoms, stroke, and ADL limitations were independently and strongly associated with lower baseline cognition scores but did not predict future cognitive decline. Each incident depressive symptom was independently associated with a 0.06-point lower (95% confidence interval (CI)=0.02-0.10) recall score, incident stroke with a 0.59-point lower total score (95% CI=0.20-0.98), each new basic ADL limitation with a 0.07-point lower recall score (95% CI=0.01-0.14) and a 0.16-point lower total score (95% CI=0.07-0.25), and each incident instrumental ADL limitation with a 0.20-point lower recall score (95% CI=0.10-0.30) and a 0.52-point lower total score (95% CI=0.37-0.67).

CONCLUSION

Prevalent and incident depressive symptoms, stroke, and ADL disabilities contribute independently to poorer cognitive functioning in older Americans but do not appear to influence rates of future cognitive decline. Prevention, early identification, and aggressive treatment of these conditions may ameliorate the burdens of cognitive impairment.

Cognitive function and antihypertensive treatment in the elderly: a 6-year follow-up study

Both antihypertensive treatment and statins were proved to reduce mortality and morbidity from cardiovascular disease in the elderly. Yet their effect on cognitive functions of the elderly is unclear. In this study, 518 elderly were interviewed at their home six years ago. BP was measured and antihypertensive drug treatment and cognitive functions were evaluated. 318 of the original sample were re-examined (81% of the survivors). We evaluated the selective survival in relation to changes in BP, the specific drug usage and cognitive functioning. Beta blocker treatment increased the odds of survival but also the odds of decline in MMSE and memory scores. ACE-I treatment was also associated with decline in memory. Subjects treated with CCB had improved MMSE scores, memory, and performed better on tasks requiring concentration. Statins treatment in this study did not show any affect on cognitive functions. Although most subjects were treated by more than one antihypertensive drug, less than half were normalized at baseline and only one quarter at follow-up. Despite the low normalization rate, antihypertensive treatment regimen had been hardly changed during the six years follow-up. The use of statins, however, increased dramatically: from 6% at baseline to almost half at follow-up. According to our findings CCB emerges as the best option for reducing BP in elderly patients. It appeared to improve cognitive functions without hampering survival.

Cognitive dysfunction in patients with type 2 diabetes

People with diabetes mellitus are at increased risk of cognitive dysfunction and dementia. This review explores the nature and severity of cognitive changes in patients with type 2 diabetes. Possible risk factors such as hypo- and hyperglycemia, vascular risk factors, micro- and macrovascular complications, depression and genetic factors will be examined, as well as findings from brain imaging and autopsy studies. We will show that type 2 diabetes is associated with modest cognitive decrements in non-demented patients that evolve only slowly over time, but also with an increased risk of more severe cognitive deficits and dementia. There is a dissociation between these two 'types' of cognitive dysfunction with regard to affected age groups and course of development. Therefore, we hypothesize that the mild and severe cognitive deficits observed in patients with type 2 diabetes reflect separate processes, possibly with different risk factors and aetiologies.

Diabetes and cognitive decline: investigating the potential influence of factors related to health disparities

OBJECTIVE

The authors investigated whether factors related to health disparities--race, rural residence, education, perceived racial discrimination, vascular disease, and health care access and utilization--may moderate the association between diabetes and cognitive decline.

METHOD

Participants were 624 community-dwelling older adults (49% African American and 49% rural) who completed in-home mini-mental state examination at baseline and 4-year follow-up.

RESULTS

Diabetes at baseline predicted four-year cognitive decline in regression models adjusted for a number of possible confounds. Only perceived discrimination and health utilization showed significant interaction effects with diabetes. Among African Americans who reported experiencing racial discrimination, there was a stronger relationship between diabetes and cognitive decline. Among participants who reported absence of visiting a physician within the past 6 months, the association between diabetes and cognitive decline was substantially larger.

DISCUSSION

Findings suggest that factors related to health disparities may influence cognitive outcomes among older adults with diabetes.

Psychiatry of old age and ethnic minority older people in the United Kingdom

This review examines the demographic changes, the epidemiology of mental disorders and suicides, the potential risk and protective factors, access to secondary care old age psychiatry services (OAPSs) and the policy context pertaining to older people from ethnic minority groups in the United Kingdom. The number of older people from ethnic minority groups is increasing. The prevalence of mental disorders in older people from ethnic minority groups is either similar to or higher than that in the indigenous population. Therefore, the number of older people from ethnic minority groups with psychiatric morbidity is also increasing. Ethnic minority older people also have inequity of access to secondary care OAPSs. There is an urgent need to develop and implement practical strategies to improve access by older people from ethnic minority groups to OAPSs.

A systematic review of the prevalence and covariates of dementia or relative cognitive impairment in the older African-Caribbean population in Britain

OBJECTIVES

To collate evidence regarding the prevalence and predictors of dementia or relative cognitive impairment in older, African-Caribbean people in Britain, as compared to their white, British peers.

DESIGN

We conducted a systematic literature review by searching electronic databases, contacting experts in the field and searching the references of identified papers for studies fulfilling our predefined inclusion criteria. They were divided into those measuring the prevalence or incidence of dementia or cognitive impairment, and those investigating risk factors. Each study selected for inclusion, was evaluated by two of the three authors using a standardised checklist and assigned a numerical score for quality.

RESULTS

Eleven papers fulfilled the selection criteria. Two cross-sectional surveys had calculated prevalence of dementia in a sample of British African-Caribbean people. A further prevalence study had estimated dementia prevalence in a mixed sample of African and African-Caribbean participants. All the comparative studies found an excess of dementia in African-Caribbean people when compared to the indigenous, white population but in one study, this was not statistically significant. Seven studies investigated potential predictive factors for cognitive impairment or cognitive decline. One study investigated the association between hypertension, dementia and country of birth.

CONCLUSIONS

The published research in this area is limited. The available studies consistently indicate an excess of dementia in older African-Caribbean people when compared to the indigenous white population. However, the magnitude of this difference and the associated risk factors are not clear, and warrant further investigation.

Education differences in life expectancy with cognitive impairment

Background

Low education has an impact on life expectancy and level of cognition, but little is known on its effect on life expectancy with cognitive impairment.

Methods

The Medical Research Council Cognitive Function and Ageing Study (MRC CFAS) collected population-based longitudinal data on people aged 65 years and older including measures of education and cognitive impairment, using the Mini-Mental State Examination (MMSE), for five geographically diverse areas around England and Wales interviewed between 1991 and 2003. Transitions between health states were calculated using Markov chain methods. Life expectancy in different states of cognitive function as measured by MMSE were further explored for different education groups. The effect of fixed and educationally based cut points for cognitive impairment are investigated.

Results

Life expectancy spent with cognitive impairment is fairly constant with increasing age at around 1.4 years in men and 2.5 years in women, though this reflects a large increase in the proportion of life spent with cognitive impairment. The differences seen between education groups for the proportion of total life with cognitive impairment (men 13% and women 22% of life lived for low education vs men 7% and women 12% in high education group) disappear when education-adjusted cut points are used (10% in men and 17% in women at age 65 for all education groups).

Conclusions

The results show that there is a substantial amount of life expectancy with cognitive impairment in both men and women. The impairment burden is just as great for those with high education as the lowest educated group.

Obesity and central obesity as risk factors for incident dementia and its subtypes: a systematic review and meta-analysis

While dementia affects 6-10% of persons 65 years or older, industrialized countries have witnessed an alarming rise in obesity. However, obesity's influence on dementia remains poorly understood. We conducted a systematic review and meta-analysis. PUBMED search (1995-2007) resulted in 10 relevant prospective cohort studies of older adults (40-80 years at baseline) with end points being dementia and predictors including adiposity measures, such as body mass index (BMI) and waist circumference (WC). There was a significant U-shaped association between BMI and dementia (P = 0.034), with dementia risk increased for obesity and underweight. Pooled odds ratios (OR) and 95% confidence intervals (CI) for underweight, overweight and obesity compared with normal weight in relation to incident dementia were: 1.36 (1.07, 1.73), 0.88 (0.60, 1.27) and 1.42 (0.93, 2.18) respectively. Pooled ORs and 95% CI for obesity and incident Alzheimer's disease (AD) and vascular dementia were 1.80 (1.00, 3.29) vs. 1.73 (0.47, 6.31) and were stronger in studies with long follow-up (>10 years) and young baseline age (<60 years). Weight gain and high WC or skin-fold thickness increased risks of dementia in all included studies. The meta-analysis shows a moderate association between obesity and the risks for dementia and AD. Future studies are needed to understand optimal weight and biological mechanisms.

Race moderates age-related cognitive decline in type 2 diabetes

The age-related rate of cognitive decline in patients with diabetes mellitus has received relatively little attention. In this cross-sectional study, Caucasian (N = 145) and African American (N = 25) males with diabetes mellitus were recruited to examine age-related changes in cognitive performance. It is known that African Americans with diabetes mellitus are at increased risk for more frequent and more severe diabetes-related complications. It was hypothesized that such complications may accelerate age-related cognitive decline in African Americans. Three timed tests varying in complexity assessed attention, mental flexibility, and learning. Advancing age was uniformly associated with decreasing cognitive performance but only on more complex tasks did race moderate this relationship. A steeper age-related decline was observed in African Americans on more complex cognitive tests. Diabetes may be an accelerated form of aging that impacts cognition and race appears to differentially moderate this relationship.

Markers of inflammation and cognitive decline in an African-Caribbean population

BACKGROUND

Inflammatory processes may play an important role in cognitive decline and dementia. We investigated the prospective association between levels of three markers of inflammation, plasma interleukin-6 (IL-6), serum C-reactive protein (CRP), serum amyloid A (SAA), and cognitive decline in an African-Caribbean community population.

METHODS

Of 290 participants aged 55-75 years at baseline sampled from Primary Care registration lists in south London, 216 (75%) were re-interviewed after 3 years. Baseline plasma concentrations of IL-6, CRP and SAA were ascertained through immunoassays. A battery of psychometric tests was administered on both occasions and decline in both individual tests and a composite outcome was analysed.

RESULTS

After adjustment for potential confounding factors, raised levels of IL-6 (>3.1 pg/ml) were associated with cognitive decline in the total sample (odds ratio 2.9, 95% CI 1.1-7.5), but no associations were found for CRP or SAA. Raised IL-6 was most strongly associated with decline in orientation and immediate verbal recall tasks, with weaker associations for delayed recall and psychomotor speed.

CONCLUSIONS

Raised IL-6 but not CRP predicted cognitive decline in this population Inflammatory changes associated with cognitive decline may be specific to particular causal pathways.

Plasma n-3 fatty acids and the risk of cognitive decline in older adults: the Atherosclerosis Risk in Communities Study

BACKGROUND

Plasma fatty acids may affect the risk of cognitive decline in older adults.

OBJECTIVES

We prospectively studied the association between plasma fatty acids and cognitive decline in adults aged 50-65 y at baseline and conducted a subgroup analysis.

DESIGN

From 1987 through 1989, the Atherosclerosis Risk in Communities (ARIC) Study analyzed plasma fatty acids in cholesteryl esters and phospholipids in whites residing in Minneapolis, MN. From 1990 through 1992 and from 1996 through 1998, 3 neuropsychological tests in the domains of delayed word recall, psychomotor speed, and verbal fluency were administered. We selected cutoffs for statistically reliable cognitive decline in each of these domains and a measure of global cognitive change computed by principal-components analysis. Multivariate logistic regression was conducted. Focusing on n-3 highly unsaturated fatty acids (HUFAs), a subgroup analysis assessed differential association across potential effect modifiers implicated in oxidative stress and increased risk of neurodegenerative disease.

RESULTS

In the 2251 study subjects, the risk of global cognitive decline increased with elevated palmitic acid in both fractions and with high arachidonic acid and low linoleic acid in cholesteryl esters. Higher n-3 HUFAs reduced the risk of decline in verbal fluency, particularly in hypertensive and dyslipidemic subjects. No significant findings were shown for psychomotor speed or delayed word recall.

CONCLUSIONS

Promoting higher intakes of n-3 HUFAs in the diet of hypertensive and dyslipidemic persons may have substantial benefits in reducing their risk of cognitive decline in the area of verbal fluency. However, clinical trials are needed to confirm this finding.

Blood Pressure Treatment and Cognition in the Elderly

While the health and longevity benefits of antihypertensive treatment have been established in past research, the cognitive consequences of blood pressure control in the elderly are still under debate. In this paper, the authors review the current evidence and the different ways in which cognition is measured. Since research on the cognitive consequences of blood pressure control in the elderly population is characterized by a variety of research questions, designs, and cognitive measurements, the authors conclude that a large-scale study that compares the cognitive benefits of different methods of blood pressure reduction is urgently needed.

Coping and psychosocial adaptation to Type 2 diabetes in older Blacks born in the Southern US and the Caribbean

Older Black men and women (n = 212) with Type 2 diabetes completed questionnaires. Spearman's rho correlation indicated that confrontive coping strategies supported effective psychosocial adaptation for persons originally from Haiti and Jamaica, while emotive coping strategies were related to ineffective psychosocial adaptation for persons originally from Barbados and to increased psychological distress for all participants. Women used more palliative coping; no gender differences were observed for psychosocial adaptation. Health care orientation, extended family relationships, and psychological distress domains distinguished Blacks born in Haiti from Blacks born in Barbados and Jamaica, the Southern US and Jamaica, and the Southern US, Barbados, and Jamaica. Findings from this study may aid in the development of interventions focused on improving diabetes self-management for older Blacks.

Leg length, cognitive impairment and cognitive decline in an African-Caribbean population

BACKGROUND

Shorter leg length is associated with an adverse environment in early childhood and has been found to be associated with a variety of disorders occurring in mid- to late-life, including dementia in a Korean population. In a community population of African-Caribbean elders, in whom leg length had been measured, we sought to compare associations with cognitive impairment at baseline and cognitive decline over a three-year follow-up period.

METHODS

Of 290 African-Caribbean residents in south London recruited at baseline, 216 (74%) were re-interviewed after a three-year period and 203 had sufficient data for this analysis. Cognitive impairment was derived as a binary category from a battery of cognitive tests administered at baseline and cognitive decline was derived from change in performance on a subset of these tests. Leg length (iliac crest to lateral malleolus) was also measured.

RESULTS

Shorter leg length was associated with female sex, lower occupational social class and reported hypertension and diabetes. Shorter leg length (lowest quartile) was significantly associated with cognitive impairment but there were no apparent associations with cognitive decline. The association with cognitive impairment was independent of age, sex and education. Social class appeared to be an important mediating factor.

CONCLUSIONS

Shorter leg length may be a marker of early life stressors which result in reduced cognitive reserve. Interestingly this association was mediated more strongly by social class (previous occupational status) than by education in this population.

Association between mind-body and cardiovascular exercises and memory in older adults

OBJECTIVES

To compare the memory function of older adults who regularly practiced mind-body (MB) or cardiovascular (CV) exercises with that of those who did not engage in regular exercise. Older adults who engaged in both types of exercise were also included to examine the combined effects.

DESIGN

Cross-sectional study between 2002 and 2003.

SETTING

Older adults from a local community in Hong Kong.

PARTICIPANTS

One hundred forty adults aged 56 and older.

MEASUREMENTS

The Hong Kong List Learning Test was used to assess the memory of all participants. It is a clinically validated Chinese verbal-memory test that measures various aspects of memory processing, including learning, retention, and retrieval abilities. MB and CV exercises were defined using three dimensions: motion speed, emphasis on relaxing the mind, and conscious control of movement.

RESULTS

Older adults who practiced MB or CV exercises demonstrated a similar level of memory function, and their learning and memory was better than that of individuals who did not exercise regularly. Those who practiced both types of exercises outperformed all other groups, even after corrected for the total hours of exercise. Although memory change across age was found in older adults who did not exercise, this trend was not observed in individuals who practiced MB exercises.

CONCLUSION

Practicing both MB and CV exercises appears to have a combined effect that might help to preserve memory in older adults. In addition, MB exercises may be considered as an alternative training for older adults who cannot practice strenuous physical exercise.

Challenges in the epidemiological investigation of the relationships between physical activity, obesity, diabetes, dementia and depression

There are many challenges facing epidemiologists wishing to investigate relationships between physical activity, obesity, diabetes, dementia and depression, all of which are complex fields in their own right. There is a large literature investigating the relationship between diabetes and dementia but less, as yet, on the other exposures and outcomes. In this literature there is a diversity of definitions making rigorous systematic review problematic. There is a need to define hypotheses in this area very clearly and to identify studies that have addressed the specific question. Such exercises have not been carried out to date but would enlighten the research area and point more clearly to questions which remain to be answered. Our own research group has examined the specific question of risk of development of dementia in relation to levels of HbA(1)c, as a marker of glycaemic control and showed that although not related to dementia, it is related to incidence of severe cognitive impairment.

Cognitive decline and dementia in diabetes--systematic overview of prospective observational studies

AIMS/HYPOTHESIS

We systematically reviewed and summarised prospective data relating diabetes status to changes in cognitive function over time.

METHODS

Published reports of longitudinal studies that described assessment of cognitive function in people with diabetes were sought. Studies were included if they assessed cognitive function in participants with diabetes at the beginning and at follow-up. Studies were excluded if they had (1) a follow-up period of less than 1 year, (2) a rate of loss to follow-up in excess of 30%, or (3) described selected subgroups. Change in cognitive function was recorded as either the mean change in score and/or the proportion of individuals developing various degrees of change in cognitive function. A pooled estimate was calculated for the latter.

RESULTS

Of 1,165 abstracts and titles initially identified, 25 articles met the inclusion and exclusion criteria. Individuals with diabetes had a 1.2- to 1.5-fold greater change over time in measures of cognitive function than those without diabetes. When assessed by the Mini-Mental State Exam and the Digit Symbol Span tests, a diagnosis of diabetes increased the odds of cognitive decline 1.2-fold (95% CI 1.05-1.4) and 1.7-fold (95% CI 1.3-2.3), respectively . The odds of future dementia increased 1.6-fold (95% CI 1.4-1.8).

CONCLUSIONS/INTERPRETATION

Compared to people without diabetes, people with diabetes have a greater rate of decline in cognitive function and a greater risk of cognitive decline. Cognitive dysfunction should therefore be added to the list of chronic complications of diabetes.

ACE genotype and cognitive decline in an African-Caribbean population

The insertion/deletion (I/D) polymorphism of the angiotensin I converting enzyme (ACE) gene is believed to influence risk of cerebrovascular disease. However, associations with cognitive outcomes remain controversial. As far as we are aware, all studies to date have been carried out in white American or European populations. African-Caribbean populations have high prevalence rates of hypertension, diabetes and cerebrovascular disease but risk factors for cognitive outcomes remain under-researched. In a UK community sample of 148 African-Caribbean people aged 55-75 years, we investigated the association between ACE genotype and cognitive decline over 3 years using a battery of repeated tests. No direct association was found between ACE genotype and decline. However, the association between increased age and cognitive decline was significantly stronger in people with the ACE DD genotype (odds ratio 3.6 per 5-year increase, 95% CI: 1.9-6.7) compared to those with ID/II genotype (odds ratio 0.7, 95% CI 0.4-1.2). This interaction was particularly strong for decline in verbal memory and was not apparently mediated by vascular risk factors measured at baseline.