The assessment of cognitive function in the German National Cohort (NAKO) - Associations of demographics and psychiatric symptoms with cognitive test performance

OBJECTIVES

To describe the cognitive test battery of the German National Cohort (NAKO), a population-based mega cohort of 205,000 randomly selected participants, and to examine associations with demographic variables and selected psychiatric and neurological conditions.

METHODS

Initial data from 96,401 participants providing data on the cognitive performance measured by a brief cognitive test battery (12-word list recall task, semantic fluency, Stroop test, digit span backwards) was examined. Test results were summarised in cognitive domain scores using exploratory and confirmatory factor analyses. Associations with sociodemographic and psychiatric factors were analysed using linear regression and generalised additive models.

RESULTS

Cognitive test results were best represented by two domain scores reflecting memory and executive functions. Lower cognitive functions were associated with increasing age and male sex. Higher education and absence of childhood trauma were associated with better cognitive function. Moderate to severe levels of anxiety and depression, and a history of stroke, were related to lower cognitive function with a stronger effect on executive function as compared to memory. Some associations with cognition differed by German language proficiency.

CONCLUSIONS

The NAKO cognitive test battery and the derived cognitive domain scores for memory and executive function are sensitive measures of cognition.

Cognition-Mortality Associations Are More Pronounced When Estimated Jointly in Longitudinal and Time-to-Event Models

With aging populations worldwide, there is growing interest in links between cognitive decline and elevated mortality risk—and, by extension, analytic approaches to further clarify these associations. Toward this end, some researchers have compared cognitive trajectories of survivors vs. decedents while others have examined longitudinal changes in cognition as predictive of mortality risk. A two-stage modeling framework is typically used in this latter approach; however, several recent studies have used joint longitudinal-survival modeling (i.e., estimating longitudinal change in cognition conditionally on mortality risk, and vice versa). Methodological differences inherent to these approaches may influence estimates of cognitive decline and cognition-mortality associations. These effects may vary across cognitive domains insofar as changes in broad fluid and crystallized abilities are differentially sensitive to aging and mortality risk. We compared these analytic approaches as applied to data from a large-sample, repeated-measures study of older adults (N = 5,954; ages 50–87 years at assessment; 4,453 deceased at last census). Cognitive trajectories indicated worse performance in decedents and when estimated jointly with mortality risk, but this was attenuated after adjustment for health-related covariates. Better cognitive performance predicted lower mortality risk, and, importantly, cognition-mortality associations were more pronounced when estimated in joint models. Associations between mortality risk and crystallized abilities only emerged under joint estimation. This may have important implications for cognitive reserve, which posits that knowledge and skills considered well-preserved in later life (i.e., crystallized abilities) may compensate for declines in abilities more prone to neurodegeneration, such as recall memory and problem solving. Joint longitudinal-survival models thus appear to be important (and currently underutilized) for research in cognitive epidemiology.

Understanding the relationship between cognition and death: a within cohort examination of cognitive measures and mortality

Despite several studies demonstrating an independent and inverse association between cognition and mortality, the nature of this association still remains unclear. To examine the association of cognition and mortality after accounting for sociodemographic, health and lifestyle factors and to explore both test and population characteristics influencing this relationship. In a population based cohort of 8585 men and women aged 48-92 years, who had cognitive assessments in 2006-2011 and were followed up till 2016 for mortality, we examined the relationship between individual cognitive tests as well as a global cognition score to compare their ability in predicting mortality and whether these differed by population characteristics. Risk of death was estimated using Cox proportional hazard regression models including sociodemographic, lifestyle and health variables, and self-reported comorbidities, as covariates in the models. Poor cognitive performance (bottom quartile of combined cognition score) was associated with higher risk of mortality, Hazard Ratio = 1.32 (95% Confidence Interval 1.09, 1.60); individual cognitive tests varied in their mortality associations and also performed differently in middle-age and older age groups. Poor cognitive performance is independently associated with higher mortality. This association is observed for global cognition and for specific cognitive abilities. Associations vary depending on the cognitive test (and domain) as well as population characteristics, namely age and education.

What Do We Know About Psychological Outcomes of Lymphoma in Adults?

Abstract. The goal of this review is to present the results of research on the influence of lymphoma on patients’ emotional status and cognitive functioning. A literature search was conducted to identify articles in English that investigated short- and long-term psychological outcomes of lymphoma and lymphoma treatment. Studies published prior to July 2016 were located by an electronic search using relevant databases such as ScienceDirect and PubMed. The search terms used included both medical subject headings and keywords such as “Hodgkin lymphoma,” “non-Hodgkin lymphoma,” “therapy,” “treatment,” “malignant,” “psychology,” “cognitive function,” “emotion,” “psychological adaptation,” “depression,” and “anxiety.” The retrieved publications were independently evaluated by two reviewers. Articles were selected based on the applicable titles and abstracts. The lists of eligible publications were compared and disagreements were resolved by discussion. Of the 1,418 articles identified in the search, we chose 39 publications, which in our opinion could be interesting or useful for psychologists. Studies show that lymphoma and its treatment lead to severe distress. Thirty-six percent of patients manifest symptoms of anxiety and depression, which are most often associated with the so-called “B-symptoms,” which mark poor prognosis or with side effects of chemotherapy such as nausea or vomiting. Reports also indicate that lymphoma patients may develop mild to severe cognitive decline. Its manifestations may range from benign problems with attention, thinking, and memory to severe cognitive impairment, that is, subcortical dementia. The etiology of intellectual deterioration in lymphoma has not been well described yet, but it may be related to the disease process or to the treatment. Additionally, literature demonstrates that lymphoma may lead to adverse changes in patient’s professional life such as resignation or early retirement.

The role of cognitive reserve on terminal decline: a cross-cohort analysis from two European studies: OCTO-Twin, Sweden, and Newcastle 85+, UK

OBJECTIVE

Cognitive performance shows a marked deterioration in close proximity to death, as postulated by the terminal decline hypothesis. The effect of education on the rate of terminal decline in the oldest people (i.e. persons 85+ years) has been controversial and not entirely understood. In the current study, we investigated the rate of decline prior to death with a special focus on the role of education and socioeconomic position, in two European longitudinal studies of ageing: the Origins of Variance in the Old-Old: Octogenarian Twins (OCTO-Twin) and the Newcastle 85+ study.

METHODS

A process-based approach was used in which individuals' cognitive scores were aligned according to distance to death. In a coordinated analysis, multilevel models were employed to examine associations between different markers of cognitive reserve (education and socioeconomic position) and terminal decline using the mini-mental state examination (MMSE), controlling for age at baseline, sex, dementia incidence and time to death from the study entry to the time of death within each cohort.

RESULTS

The current findings suggest that education was positively associated with higher MMSE scores prior to death in the OCTO-Twin, but not in the Newcastle 85+ study, independent of socioeconomic position and other factors such as baseline age, sex and time to death from the study entry. However, education was not associated with the rate of terminal decline in both of these studies.

CONCLUSIONS

Our results offer only partial support to the cognitive reserve hypothesis and cognitive performance prior to death.

Think Fast, Feel Fine, Live Long: A 29-Year Study of Cognition, Health, and Survival in Middle-Aged and Older Adults

In a 29-year study of 6,203 individuals ranging in age from 41 to 96 years at initial assessment, we evaluated the relative and combined influence of 65 mortality risk factors, which included sociodemographic variables, lifestyle attributes, medical indices, and multiple cognitive abilities. Reductions in mortality risk were most associated with higher self-rated health, female gender, fewer years as a smoker, and smaller decrements in processing speed with age. Thus, two psychological variables-subjective health status and processing speed-were among the top predictors of survival. We suggest that these psychological attributes, unlike risk factors that are more narrowly defined, reflect (and are influenced by) a broad range of health-related behaviors and characteristics. Information about these attributes can be obtained with relatively little effort or cost and-given the tractability of these measures in different cultural contexts-may prove expedient for prevention, diagnosis, and treatment of conditions related to increased mortality risk in diverse human populations.

Cognition and mortality in older people: the Sydney Memory and Ageing Study

BACKGROUND

Both cognitive ability and cognitive decline have been shown to predict mortality in older people. As dementia, a major form of cognitive decline, has an established association with shorter survival, it is unclear the extent to which cognitive ability and cognitive decline predict mortality in the absence of dementia.

OBJECTIVE

To determine whether cognitive ability and decline in cognitive ability predict mortality in older individuals without dementia.

DESIGN

The Sydney Memory and Ageing Study is an observational population-based cohort study. Participants completed detailed neuropsychological assessments and medical examinations to assess for risk factors such as depression, obesity, hypertension, diabetes, hypercholesterolaemia, smoking and physical activity. Participants were regularly assessed at 2-year intervals over 8 years.

SETTING

A community sample in Sydney, Australia.

SUBJECTS

One thousand and thirty-seven elderly people without dementia.

RESULTS

Overall, 236 (22.8%) participants died within 8 years. Both cognitive ability at baseline and decline in cognitive ability over 2 years predicted mortality. Decline in cognitive ability, but not baseline cognitive ability, was a significant predictor of mortality when depression and other medical risk factors were controlled for. These relationships also held when excluding incident cases of dementia.

CONCLUSIONS

The findings indicate that decline in cognition is a robust predictor of mortality in older people without dementia at a population level. This relationship is not accounted for by co-morbid depression or other established biomedical risk factors.

Gene-environment interaction of body mass index and apolipoprotein E ε4 allele on cognitive decline

Genetic variation alone may not account for common chronic disease susceptibility. Rather, an interaction between genetic and environmental factors may clarify the underlying disease mechanism. Hence, we tested whether body mass index (BMI) modified the genetic association of the apolipoprotein E ε4 allele with cognitive decline. The data came from a longitudinal population-based sample of 4055 participants interviewed at 3-year intervals from 1993 to 2012. Cognitive function was assessed using a standardized global cognitive score and BMI was assessed at baseline and classified as normal, overweight, and obese. There were 1374 (34%) participants with the ε4 allele. In normal BMI participants, cognitive decline was 0.048 units/y without the ε4 allele, and increased by an additional 0.031 units/y with the ε4 allele. In overweight participants, cognitive decline was 0.038 units/y without the ε4 allele, and increased by an additional 0.026 units/y with the ε4 allele. Finally, in obese participants, cognitive decline was 0.038 units/y without the ε4 allele, and increased by an additional 0.014 units/y with the ε4 allele. The association of ε4 allele with cognitive decline was significantly lower in obese participants compared with normal BMI participants (P=0.003), thereby suggesting significant gene-environment interaction on cognitive decline.

Cognitive impairment before and six months after cardiac surgery increase mortality risk at median 11 year follow-up: a cohort study

BACKGROUND

The additive effects of cognitive impairment and depression on mortality risk after cardiac surgery are unknown.

METHODS

Patients were assessed on a battery of six neurocognitive measures before cardiac surgery (N = 521) and at six month follow up (N = 377/521, 72.4%). Cognitive impairment classification was based on cognitive test scores 1 SD below age and sex matched normative data, and classified according to amnestic, non-amnestic and mixed cognitive impairment subtypes. Survival analyses entered cognitive impairment subtypes and depression interactions terms adjusted for 12 common risk factors.

RESULTS

There were 5407 person years for analysis (median 11.1 year survival, interquartile range of 7.9 to 13.1) and 176 deaths (33.8%) by the census date. Before cardiac surgery, patients with a mixed-cognitive impairment (adjusted hazard ratio (HR) = 2.53; 95% confidence interval (CI), 1.57-4.06, p<.001) and non-amnestic cognitive impairment (adjusted HR = 1.51; 95%, 1.00-2.32, p = .05) were at greater mortality risk. Six month analyses corroborated that the mixed-cognitive impairment group were at higher mortality risk (adjusted HR = 2.35; 95% CI, 1.30-4.25, p = .005). When change in neurocognitive functioning over time was analyzed, a higher mortality risk was evident only amongst patients with cognitive impairment evident at baseline and six months (adjusted HR = 1.83; 95% CI, 1.08-3.10, p = .03). No cognition by depression interaction term was significant.

CONCLUSIONS

These data suggest that a mixed cognitive impairment subtype, and continuing cognitive impairment before and six months after cardiac surgery, is associated with long term mortality, independent of depression and common risk factors.

Disability in basic and instrumental activities of daily living is associated with faster rate of decline in cognitive function of older adults

BACKGROUND

The purpose of this study is to examine whether physical disability is associated with faster rate of decline in cognitive function.

METHODS

A longitudinal population-based cohort of 6,678 initially nondisabled older adults from a biracial urban community was interviewed at 3-year intervals from 1993 to 2012. Cognitive function was assessed using a standardized global cognitive score, and physical disabilities using activities of daily living (ADL) and instrumental activities of daily living (IADL).

RESULTS

During the follow-up period, 2,450 of 6,678 participants (37%) developed ADL and 2,069 of 4,287 participants (48%) developed IADL disability. After adjusting for demographic and physiologic confounders, cognitive function declined a mean of 0.048 unit per year before ADL disability and 0.047 unit per year before IADL disability. In comparison, the rate of cognitive decline accelerated further by 0.076 unit per year (156% increase) after ADL disability and 0.054 unit per year (115% increase) after IADL disability. Severity of ADL and IADL disabilities were also associated with faster cognitive decline following disability.

CONCLUSIONS

In old age, cognitive function declines substantially faster following physical disability even after controlling for demographic and physiologic characteristics of participants.

An evaluation of analytical approaches for understanding change in cognition in the context of aging and health

OBJECTIVES

In this article, we discuss the importance of studying the relationship between health and cognitive function, and some of the methods with which this relationship has been studied.

METHODS

We consider the challenges involved, in particular operationalization of the health construct and causal inference in the context of observational data. We contrast the approaches taken, and review the questions addressed: whether health and cognition are associated, whether changes in health are associated with changes in cognition, and the degree of interdependency among their respective trajectories.

RESULTS

A variety of approaches for understanding the association between cognition and health in aging individuals have been used. Much of the literature on cognitive change and health has relied on methods that are based at least in part on the reorganization of between-person differences (e.g., cross-lag analysis) rather than relying more fully on analysis of within-person change and joint analysis of individual differences in within-person change in cognition and health.

DISCUSSION

We make the case for focusing on the interdependency between within-person changes in health and cognition and suggest methods that would support this.

Aging and the shape of cognitive change before death: terminal decline or terminal drop?

OBJECTIVES

Relative to typical age-related cognitive decrements, the terms "terminal decline" and "terminal drop" refer to the phenomenon of increased cognitive decline in proximity to death. Given that these terms are not necessarily synonymous, we examined the important theoretical distinction between the two alternative trajectories or shapes of changes they imply.

METHODS

We used 12-year (5-wave) data from the Victoria Longitudinal Study to directly test whether pre-death cognitive decrements follow a terminal decline (generally gradual) or a terminal drop (more abrupt) shape. Pre-death trajectories of cognitive decline for n=265 decedents (Mage = 72.67 years, SD = 6.44) were examined separately for 5 key cognitive constructs (verbal speed, working memory, episodic memory, semantic memory, and crystallized ability).

RESULTS

Several classes of linear mixed models evaluated whether cognitive decline increased per additional year closer to death. Findings indicated that the shape of pre-death cognitive change was predominantly characterized by decline that is steeper as compared with typical aging-related change, but still best described as slow and steady decline, especially as compared with precipitous drop.

DISCUSSION

The present findings suggest that terminal decline and terminal drop trajectories may not be mutually exclusive but could rather reflect distinct developmental trajectories within the same individual.

Cognition and mortality from the major causes of death: the Health and Lifestyle Survey

OBJECTIVE

To investigate the influence of reaction time and cognition on the risk of death from cause-specific mortality and to examine whether any association found remains after adjustment for available socioeconomic, lifestyle, and health factors.

METHODS

Participants were from the UK Health and Lifestyle Survey. The sample consisted of 6424 community dwelling individuals aged between 18 and 97 years at baseline (1984/1985). Sociodemographic, lifestyle, health, and physiological information was collected alongside cognitive testing which included simple (SRT) and choice (CRT) reaction time, a short-term memory test, and a test of visual-spatial reasoning. Participants have been followed for 21 years for cause-specific mortality.

RESULTS

Slower and more variable reaction times and poorer cognitive performance were associated with a higher risk of death from cardiovascular disease, stroke, and respiratory disease after controlling for age and sex. Slight attenuation was noted after adjustments for all covariates. However, only CRT mean remained significantly associated with death from respiratory disease. No associations were found for coronary heart disease, lung cancer, and all nonlung cancers. Significant cognition-mortality associations were mostly obtained in those aged over 60 years. The possibility of reverse causality was partly excluded by reanalysing the data after omitting individuals who died within 5 years of cognitive testing.

CONCLUSIONS

Slower and more variable reaction times and poorer cognitive performance were related to an increased risk of mortality from cardiovascular disease, stroke, and respiratory disease. The possibility of reverse causality requires further testing.

Application of a joint multivariate longitudinal-survival analysis to examine the terminal decline hypothesis in the Swiss Interdisciplinary Longitudinal Study on the Oldest Old

In this work I aim at extending current knowledge on the terminal decline hypothesis by applying a joint multivariate longitudinal-survival analysis to the cognitive data of the Swiss Interdisciplinary Longitudinal Study on the Oldest Old. (In that study, 529 individuals between 79 and 85 years of age at study inception were assessed up to five times on a task of perceptual speed and one of verbal fluency.) I simultaneously estimated a multivariate, multilevel longitudinal model and a Weibull survival model to test whether individual performance and change in speed and fluency predict survival, controlling for retest effects, initial age, gender, overall health, socioeconomic status, and sensory functioning. Results revealed that age and performance level in fluency predicted survival, whereas level in speed and change in both cognitive variables did not. I discuss the relevance of fluency tasks in predicting mortality.

Cognitive impairment as assessed by a short form of MMSE was predictive of mortality

OBJECTIVE

This study explores the association between cognitive impairment and mortality in late senescence. A specific purpose was to validate the ability of a short form of the Mini-Mental State Examination (MMSE) in predicting mortality.

STUDY DESIGN AND SETTING

The cognition-mortality link, as assessed by the original MMSE and D-MMSE (a subscale associated to dementia) was estimated on a community sample of 1,111 older people using Cox proportional hazards models.

RESULTS

Impaired cognitive function as assessed by both the original MMSE and D-MMSE predicted mortality in older men and women over long intervals. The association persisted after controlling for sociodemographic variables, Body Mass Index, mobility, and comorbidity and was unaffected by self-reported specific chronic diseases in both men and women. In addition, disease related risk of mortality was substantially reduced by sociodemographic and health variables including cognitive functioning. Only in women, stroke and diabetes remained statistically significant associated with mortality.

CONCLUSION

The association between cognitive impairment and mortality reflects processes different from those underlying a simple relation between chronic diseases and mortality. A short, valid MMSE subscale, which was a powerful predictor of mortality especially among men, is attractive for research and clinical practice.

Association between mortality and cognitive change over 7 years in a large representative sample of UK residents

OBJECTIVE

To examine the association between change in reaction time and cognitive performance over 7 years and the risk of death from all causes and some specific causes after controlling for known risk factors.

METHODS

The sample comprised members of the Health and Lifestyle Survey (HALS) of community-dwelling adults in England, Scotland, and Wales. Baseline testing (HALS1), involving 9003 people, took place in 1985 and 1986. Sociodemographic, lifestyle, health, and physiological information was collected. Cognitive functioning was measured using tests of simple and choice reaction time, a short memory test, and a test of visual-spatial reasoning. Follow-up testing (HALS2) took place in 1991 and 1992, when 5352 members of the study were administered the same questionnaires, physiological examinations, and cognitive tests. The sample has been followed for mortality up to June 2005.

RESULTS

After controlling for age, gender, and the relevant baseline cognitive test scores, greater declines between HALS1 and HALS2 on simple reaction time mean and variability, choice reaction time mean and variability, memory and visual-spatial reasoning were associated with significantly increased risks of death from all causes, all cardiovascular diseases (CVDs), coronary heart disease (CHD), stroke, and respiratory disease. These associations were only slightly attenuated after adjusting for occupational social class, educational, smoking, alcohol consumption, physical activity, body mass index, blood pressure, and lung function.

CONCLUSIONS

Decline in performance of reaction times and simple cognitive tasks across a 7-year period was associated with an increased risk of death from all causes, all CVDs, CHD, stroke, and respiratory disease up to 13 years later, even after adjustment for known risk factors.