Ross Andel

The effect of education and occupational complexity on rate of cognitive decline in Alzheimer's patients

We explored the effect of education and occupational complexity on the rate of cognitive decline (as measured by the Mini-Mental State Examination) in 171 patients with a confirmed Alzheimers disease (AD) diagnosis. Complexity was measured as substantive complexity of work and complexity of work with data, people, and things. Average lifetime occupational complexity was calculated based on years at each occupation. Participants were followed for an average of 2.5 years and 3.7 visits. In multivariate mixed-effects models, high education, high substantive complexity, and high complexity of work with data and people predicted faster rates of cognitive decline, controlling for age, gender, native language, dementia severity, and entry into the analyses at initial versus follow-up testing. These results provide support for the concept of cognitive reserve according to which greater reserve may postpone clinical onset of AD but also accelerate cognitive decline after the onset.

Risk factors for nursing home placement in older adults with and without dementia.

Objective: The authors explored the effect of predisposing, enabling, and need characteristics on risk of nursing home placement (NHP) in participants with and without dementia. Method: Participants were 1,943 newly enrolled Medicare/Medicaid beneficiaries in Florida who were evaluated for health services by the Department of Elder Affairs. They were at least 65 years of age during fiscal year 1998-1999 and were followed for up to 4 years. Results: Cox proportional hazard regressions indicated that baseline characteristics including older age, White race, diabetes, incontinence, stroke, and difficulties with instrumental activities increased risk of NHP in those without dementia. Caregiver, widowed status, arthritis, and heart disease reduced the risk. Only age, race, and marital status were predictive among participants with dementia. Discussion: Dementia plays a central role in risk of NHP. Understanding risk factors for NHP in this relatively vulnerable population has important policy implications.

The Role of Occupational Complexity in Trajectories of Cognitive Aging Before and After Retirement

We examined the association between complexity of the main lifetime occupation and changes in cognitive ability in later life. Data on complexity of work with data, people, and things and on 4 cognitive factors (verbal, spatial, memory, and speed) were available from 462 individuals in the longitudinal Swedish Adoption/Twin Study of Aging. Mean age at the first measurement wave was 64.3 years (SD = 7.2), and 65% of the sample had participated in at least three waves of data collection. Occupational complexity with people and data were both correlated with cognitive performance. Individuals with more complex work demonstrated higher mean performance on the verbal, spatial, and speed factors. Latent growth curve analyses indicated that, after correcting for education, only complexity with people was associated with differences in cognitive performance and rate of cognitive change. Continued engagement as a result of occupational complexity with people helped to facilitate verbal function before retirement, whereas a previous high level of complexity of work with people was associated with faster decline after retirement on the spatial factor.

Spatial navigation testing discriminates two types of amnestic mild cognitive impairment

The hippocampus is essential for consolidation of declarative information and spatial navigation. Alzheimers disease (AD) diagnosis tends to be preceded by a long prodromal period and mild cognitive impairment (MCI). Our goal was to test whether amnestic MCI comprises two different subgroups, with hippocampal and non-hippocampal memory impairment, that vary with respect to spatial navigation ability. A total of 52 patients were classified into two subgroups: non-amnestic MCI (naMCI) (n=10) and amnestic MCI (aMCI) (n=42). The aMCI subgroup was further stratified into memory impairment of hippocampal type-hippocampal aMCI (HaMCI) (n=10) (potential preclinical AD) and isolated retrieval impairment-non-hippocampal (NHaMCI) (n=32). Results were compared to control (n=28) and AD (n=21) groups. We used the Hidden Goal Task, a human analogue of the Morris Water Maze, to examine spatial navigation either dependent (egocentric) or independent of individuals position (allocentric). Overall, the HaMCI group performed poorer on spatial navigation than the NHaMCI group, especially in the latter trials when the HaMCI group exhibited limited capacity to learn and the NHaMCI group exhibited a learning effect. Finally, the HaMCI group performed almost identically as the AD group. Spatial navigation deficit is particularly pronounced in individuals with hippocampus-related memory impairment and may signal preclinical AD.

Mentally Stimulating Activities at Work During Midlife and Dementia Risk After Age 75: Follow-Up Study From the Kungsholmen Project

OBJECTIVES Previous research has suggested that mental stimulation in different life periods may protect against dementia or delay disease onset. This study aimed to explore the association between work complexity factors at midlife and dementia risk in late life under the hypothesis that high work complexity may modulate the increased dementia risk due to low education. DESIGN Population-based follow-up study. SETTING Urban. PARTICIPANTS A cohort of 931 nondemented subjects, aged 75+ years from the Kungsholmen Project, Stockholm, examined twice over 6 years. MEASUREMENTS Incident dementia cases were identified using Diagnostic and Statistical Manual of Mental Disorders, 3rd-Edition Revised criteria. Primary occupations were assigned into categories according to the Nordic Occupational Classification and matched to the 1970 U.S. Census to score the level of work complexity with data, people, and things by using a preformed matrix. RESULTS Lower dementia risk was associated with complexity of work with both data (age and gender adjusted relative risk [aRR]: 0.85, 95% confidence interval [CI]: 0.75-0.95) and with people (aRR: 0.88, 95% CI: 0.80-0.97). Adjusting for education led to similar results, although no longer statistically significant. Further, the highest degrees of complexity of work with data that involves analyzing, coordinating, and synthesizing data were associated with lower dementia risk even among lower educated subjects (relative risk: 0.52, 95% CI: 0.29-0.95). No gender differences were detected. CONCLUSIONS This study suggests that work complexity with data and people is related to lower risk of dementia and that the highest levels of work complexity may modulate the higher dementia risk due to low education.

Is Complexity of Work Associated with Risk of Dementia? The Canadian Study of Health and Aging

The authors evaluated the association of complexity of work with data, people, and things with the incidence of dementia, Alzheimers disease, and vascular dementia in the Canadian Study of Health and Aging, while adjusting for work-related physical activity. The Canadian Study of Health and Aging is a 10-year population study, from 1991 to 2001, of a representative sample of persons aged 65 years or older. Lifetime job history allowed application of complexity scores and classification of work-related physical activity. Analyses included 3,557 subjects, of whom 400 were incident dementia cases, including 299 with Alzheimers disease and 93 with vascular dementia. In fully adjusted Cox regression models, high complexity of work with people or things reduced risk of dementia (hazard ratios were 0.66 (95% confidence interval: 0.44, 0.98) and 0.72 (95% confidence interval: 0.52, 0.99), respectively) but not Alzheimers disease. For vascular dementia, hazard ratios were 0.36 (95% confidence interval: 0.15, 0.90) for high complexity of work with people and 0.50 (95% confidence interval: 0.25, 1.00) for high complexity of work with things. Subgroup analyses according to median duration (23 years) of principal occupation showed that associations with complexity varied according to duration of employment. High complexity of work appears to be associated with risk of dementia, but effects may vary according to subtype.

The Effects of Resistance Training and Walking on Functional Fitness in Advanced Old Age

The authors assessed the effects of resistance training and walking exercise on measures of functional fitness. Sixty-four volunteers (average age 83.5 years) from an independent-living facility were randomly assigned to walking, resistance training, or control groups. Participants in the walking and resistance-training groups engaged in two exercise sessions per week for 16 weeks. Measures of functional fitness included upper and lower body strength, hip and shoulder flexibility, agility and balance, coordination, blood pressure, and resting heart rate. Repeated measures analysis of variance was used to examine pretest to posttest differences. Both exercise groups showed significant improvements relative to control group in upper and lower body strength, shoulder flexibility, and agility and balance exercise. Findings demonstrate that exercise can lead to improvements in multiple domains of functional fitness even among very old, previously sedentary individuals, possibly making activities of daily living easier to perform.

Midlife Fruit and Vegetable Consumption and Risk of Dementia in Later Life in Swedish Twins

OBJECTIVE Diet may be associated with risk of dementia and Alzheimer disease (AD). The authors examined the association between fruit and vegetable consumption in midlife and risk for all types of dementia and AD. METHODS Participants were 3,779 members of the Swedish Twin Registry who completed a diet questionnaire approximately 30 years before cognitive screening and full clinical evaluation for dementia as part of the study of dementia in Swedish Twins (HARMONY) study. Among the participants, 355 twins were diagnosed with dementia. Among these, 81 twin pairs were discordant for dementia (50 discordant for AD). Data were analyzed with logistic regression for the entire sample using generalized estimating equations to adjust for relatedness of twins and with conditional logistic regression for the co-twin control design. RESULTS In fully adjusted models, a medium or great proportion of fruits and vegetables in the diet, compared with no or small, was associated with a decreased risk of dementia and AD. This effect was observed among women and those with angina. Similar, but nonsignificant, odds ratios were found in the co-twin control analyses. CONCLUSION The findings suggest that higher fruit and vegetable consumption may reduce the risk of dementia, especially among women and those with angina pectoris in midlife.

Complexity of Primary Lifetime Occupation and Cognition in Advanced Old Age

Objectives: The authors explored the association between complexity of primary lifetime occupation and cognition in older adulthood. Method: The study included 386 participants from the Swedish Panel Study of Living Conditions of the Oldest Old, a nationally representative sample aged 77 years or older. The authors examined complexity of work with data, people, and things in relation to cognitive functioning, measured with a shortened version of Mini-Mental State Examination (MMSE) and cognitive impairment based on MMSE score cutoff. Results: Complexity of work with data and people were associated with better MMSE scores, controlling for age, sex, childhood socioeconomic status, and education. The association between complexity of work with data and MMSE remained statistically significant when adult occupational status was substituted for education as a covariate. Discussion: Complexity of primary lifetime occupation may be reflected in cognitive functioning even in advanced old age. This effect may be independent of education or occupational status.

Personality and Risk of Cognitive Impairment 25 Years Later

The authors examined the relationship between personality and cognitive impairment in 4,039 members of the Swedish Twin Registry. Neuroticism and extraversion scores were collected in 1973 at midlife, and cognitive impairment was assessed in the same group 25 years later. Data were analyzed with case-control and co-twin control designs. Greater neuroticism was associated with higher risk of cognitive impairment in the results from case-control, but not from co-twin, analyses. Compared with both extraversion and introversion, moderate extraversion was associated with lower risk of cognitive impairment in both case-control and co-twin designs, as was the combination of high neuroticism and low extraversion. Findings are discussed in the context of theories related to personality, psychological distress, arousal, and cognitive function.