Not your parents' test scores: cohort reduces psychometric aging effects

Direct Effect of Life-Course Socioeconomic Status on Late-Life Cognition and Cognitive Decline in the Rush Memory and Aging Project

The role of socioeconomic status (SES) across the life course in late-life cognition is unclear. We tested the hypotheses that: 1) High SES in childhood, young adulthood, midlife, and late life have independent causal effects on higher cognition level and slower cognitive decline; 2) Compared with stable low SES (referent), stable high SES has the largest estimated effect for higher cognition level and slower decline among life-course SES combinations. The Rush Memory and Aging Project enrolled 1,940 dementia-free older adults in northeastern Illinois (1997-2018). We used inverse probability-weighted marginal structural models to estimate the joint and independent effect of each life-course SES on global and domain-specific cognition. A total of 1,746 participants had, on average, 6 years of follow-up. High SES at each life-course stage starting in young adulthood had a protective estimated effect on global and domain-specific cognition intercepts. Compared with consistently low SES, consistently high SES (β = 0.64, 95% confidence interval: 0.48, 0.93) and high SES beyond childhood (β = 0.64, 95% confidence interval: 0.47, 0.83) had the largest benefit for global cognition intercepts. None of the life-course SES measures influenced rate of global or domain-specific decline. Additional understanding of life-course SES components influencing cognitive level is warranted.

Today's Older Adults Are Cognitively Fitter Than Older Adults Were 20 Years Ago, but When and How They Decline Is No Different Than in the Past

History-graded increases in older adults' levels of cognitive performance are well documented, but little is known about historical shifts in within-person change: cognitive decline and onset of decline. We combined harmonized perceptual-motor speed data from independent samples recruited in 1990 and 2010 to obtain 2,008 age-matched longitudinal observations (M = 78 years, 50% women) from 228 participants in the Berlin Aging Study (BASE) and 583 participants in the Berlin Aging Study II (BASE-II). We used nonlinear growth models that orthogonalized within- and between-person age effects and controlled for retest effects. At age 78, the later-born BASE-II cohort substantially outperformed the earlier-born BASE cohort (d = 1.20; 25 years of age difference). Age trajectories, however, were parallel, and there was no evidence of cohort differences in the amount or rate of decline and the onset of decline. Cognitive functioning has shifted to higher levels, but cognitive decline in old age appears to proceed similarly as it did two decades ago.

The role of school education in time-dependent changes of cognitive abilities in cohorts from midlife to old age

OBJECTIVES

It is examined whether older adults' cognitive ability in terms of delayed recall and verbal fluency is improving over time, whether this occurs over all educational levels and both sexes, and whether these changes are due to increasing proportions of individuals with higher education.

METHODS

Analyses are based on the German samples of the Survey on Health, Ageing and Retirement in Europe (waves 2004 and 2013).

RESULTS

Achievement levels increased over time and in all age groups. Improvements over educational levels occurred in parallel, differences between educational levels in the earlier survey were later reproduced at higher levels. Increasing proportions of individuals with higher education did not explain improvements of cognitive ability. No sex differences emerged.

CONCLUSION

Improved cognitive abilities could not be explained by upward shifts of educational levels. Improvements in higher age groups may foster improved health status and prolonged self-determined life in the older population.

Increasingly capable at the ripe old age? Cognitive abilities from 2004 to 2013 in Germany, Spain, and Sweden

Background

Life expectancy is increasing in most high-income countries, but gains in life years are maximized if spent in good health and if cognitive abilities are maintained until old age. Age-related decline of cognitive abilities does nevertheless occur, but the pace of decline is decisive. This was the starting point for our study that aims to examine cohort effects of cognitive aging in women and men in Germany, Spain and Sweden by analyzing changes from 2004 to 2013 by estimating cohort effects within age groups starting from the age of 50 years.

Methods

A cohort study was conducted that was based on data of the surveys 2004 (N = 6,081) and 2013 (N = 8,650) from the Survey of Health, Ageing and Retirement in Europe (SHARE). The analyses were based on data of female and male respondents aged 50 years and older. Age-specific means of verbal fluency and delayed recall from the German, Spanish and Swedish samples were the cognitive domains considered in the study.

Results

In both domains of cognitive ability the achievements in the later surveys were higher than in the earlier ones. This was found in all countries, abut achievement levels increased markedly in the German and the Spanish samples, while the scores of the Swedish samples were not significantly different.

While the highest scores were found for Sweden, Germany ranked in the middle and the lowest scores were found in the Spanish samples. Over time, the scores of the German samples approached those of Sweden.

Conclusions

From the first to the second survey, improvements of older adults’ cognitive abilities were found for all countries considered. This may indicate improvements of the underlying educational systems, but also increasingly stimulating general living conditions.

Birth cohort differences in cognitive performance in 75- and 80-year-olds: a comparison of two cohorts over 28 years

Objective

To evaluate cohort differences in cognitive performance in older men and women born and assessed 28 years apart.

Methods

Data in this study were drawn from two age-homogeneous cohorts measured in the same laboratory using the same standardized cognitive performance tests. Participants in the first cohort were born in 1910 and 1914 and assessed in 1989–1990 (Evergreen project, n = 500). Participants in the second cohort were born in 1938 or 1939 and 1942 or 1943 and assessed in 2017–2018 (Evergreen II, n = 726). Participants in both cohorts were assessed at age 75 and 80 years and were recruited from the population register. Cognitive performance was measured using the Digit Span test from the Wechsler Memory Scale (WMS), Digit Symbol test from the Wechsler Adult Intelligence Scale (WAIS) and phonemic Verbal Fluency test from the Schaie-Thurstone Adult Mental Abilities Test. Reaction time assessing motor and mental responses was measured with a simple finger movement task, followed by a complex finger movement task. T-tests were used to study cohort differences and linear regression models to study possible factors underlying differences.

Results

We found statistically significant cohort differences in all the cognitive performance tests, except for the digit span test and simple movement task in men, the later-born cohort performing better in all the measured outcomes.

Conclusions

The results of this study provide strong evidence that cognitive performance is better in more recent cohorts of older people compared to their counterparts measured 28 years earlier.

Secular trends in cognitive trajectories of diverse older adults

INTRODUCTION

This study aimed to determine if later birth year influences trajectory of age-related cognitive decline across racial/ethnic groups and to test whether years of school, childhood socioeconomic status, and cardiovascular disease burden explain such secular trends.

METHODS

We compared cognitive trajectories of global cognition and subdomains in two successive racially/ethnically and educationally diverse birth cohorts of a prospective cohort study.

RESULTS

Later birth year was associated with higher initial cognitive levels for Whites and Blacks, but not Hispanics. Later birth year was also associated with less rapid rate of decline in all three racial/ethnic groups. More years of education, higher childhood socioeconomic status, and, to a smaller extent, greater cardiovascular disease burden accounted for higher intercepts in the later-born cohort, but did not account for attenuated slope of cognitive decline.

DISCUSSION

Later birth year is related to a slower rate of age-related decline in some cognitive domains in some racial/ethnic groups. Our analyses suggest that racial/ethnic and social inequalities are part of the mechanisms driving secular trends in cognitive aging and dementia.

Cohort Differences in Cognitive Aging in the Longitudinal Aging Study Amsterdam

Objectives

This study aims to examine cohort differences in cognitive performance and rates of change in episodic memory, processing speed, inductive reasoning, and general cognitive performance and to investigate whether these cohort effects may be accounted for by education attainment.

Method

The first cohort (N = 705) was born between 1920 and 1930, whereas the second cohort (N = 646) was born between 1931 and 1941. Both birth cohorts were aged 65 to 75 years at baseline and were followed up 3 and 6 years later. Data were analyzed using linear mixed models.

Results

The later born cohort had better general cognitive performance, inductive reasoning, and processing speed at baseline, but cohort differences in inductive reasoning and general cognitive performance disappeared after adjusting for education. The later born cohort showed steeper decline in processing speed. Memory decline was steeper in the earlier born cohort but only from Time 1 to Time 3 when the same memory test was administered. Education did not account for cohort differences in cognitive decline.

Discussion

The later born cohort showed better initial performance in certain cognitive abilities, but no better preservation of cognitive abilities overtime compared with the earlier born cohort. These findings carry implications for healthy cognitive aging.

Recent Improvements in Cognitive Functioning Among Older U.S. Adults: How Much Does Increasing Educational Attainment Explain?

OBJECTIVES

Recent interest has been generated about reports of declining incidence in cognitive impairment among more recently born cohorts. At the same time, attained education, which is related to cognition, has increased in recent cohorts of older adults. We examined cohort differences in cognitive function in a nationally representative sample of Americans aged 25 and older followed for 25 years (1986-2011) and considered the extent to which cohort differences in education account for differences.

METHOD

Data come from the Americans' Changing Lives Study (N = 3,617). Multiple cohort latent growth models model trajectories of cognition (errors on the Short Portable Mental Status Questionnaire) across four 15-year birth cohorts. Demographic factors, educational attainment, and time-varying health conditions were covariates.

RESULTS

Significant cohort differences were found in the mean number of cognitive errors (e.g., 0.26 more errors at age 65 in cohort born pre-1932 vs cohort born 1947-1961, p < .001). Although demographic and health conditions were associated with level and rate of change in cognitive dysfunction, education solely accounted for cohort differences.

DISCUSSION

Compression of cognitive morbidity is seen among the highly educated, and increasing educational opportunities may be an important strategy for decreasing the risk for cognitive impairment in later life.

Temporal Trends in the Level and Decline of Cognition and Disability in an Elderly Population: The PAQUID Study

In line with declining trends in dementia incidence, we compared the cognitive and functional evolution of 2 "generations" of elderly individuals aged 78-88 years, who were included 10 years apart in the French Personnes Agées Quid cohort (n = 612 in 1991-1992 and n = 628 in 2001-2002) and followed-up for 12 years with assessments of cognition and disability. The impact of specific risk factors on this evolution was evaluated. Differences between the generations in baseline levels and decline over time were estimated using a joint model to account for differential attrition. Compared with the first generation, the second generation had higher performances at baseline on 4 cognitive tests (from P < 0.005). Differences in global cognition, verbal fluency, and processing speed, but not in working memory, were mostly explained by improvement in educational level. The second generation also exhibited less cognitive decline in verbal fluency and working memory. Progression of disability was less over the follow-up period for the second generation than for the first. The cognitive state of this elderly population improved, partially due to improvements in educational level.

Better Cognition in New Birth Cohorts of 70 Year Olds, But Greater Decline Thereafter

OBJECTIVES

To evaluate birth cohort differences in level of cognition and rate of change in old age.

METHODS

Data were drawn from three population-based Swedish samples including age-homogenous cohorts born 1901/02, 1906/07, and 1930, and measured on the same cognitive tests at ages 70, 75, and 79 as part of the Gerontological and Geriatric Populations Studies in Gothenburg (H70). We fitted growth curve models to the data using a Bayesian framework and derived estimates and inferences from the marginal posterior distributions.

RESULTS

We found moderate to large birth cohort effects in level of performance on all cognitive outcomes. Later born cohorts, however, showed steeper linear rate of decline on reasoning, spatial ability, and perceptual- and motor-speed, but not on picture recognition memory and verbal ability.

DISCUSSION

These findings provide strong evidence for substantial birth cohort effects in cognition in older ages and emphasize the importance of life long environmental factors in shaping cognitive aging trajectories. Inferences from cognitive testing, and standardization of test scores, in elderly populations must take into account the substantial birth cohort differences.

Confirming the cognition of rising scores: Fox and Mitchum (2013) predicts violations of measurement invariance in series completion between age-matched cohorts

The trend of rising scores on intelligence tests raises important questions about the comparability of variation within and between time periods. Descriptions of the processes that mediate selection of item responses provide meaningful psychological criteria upon which to base such comparisons. In a recent paper, Fox and Mitchum presented and tested a cognitive theory of rising scores on analogical and inductive reasoning tests that is specific enough to make novel predictions about cohort differences in patterns of item responses for tests such as the Raven’s Matrices. In this paper we extend the same proposal in two important ways by (1) testing it against a dataset that enables the effects of cohort to be isolated from those of age, and (2) applying it to two other inductive reasoning tests that exhibit large Flynn effects: Letter Series and Word Series. Following specification and testing of a confirmatory item response model, predicted violations of measurement invariance are observed between two age-matched cohorts that are separated by only 20 years, as members of the later cohort are found to map objects at higher levels of abstraction than members of the earlier cohort who possess the same overall level of ability. Results have implications for the Flynn effect and cognitive aging while underscoring the value of establishing psychological criteria for equating members of distinct groups who achieve the same scores.

The association between higher order abilities, processing speed, and age are variably mediated by white matter integrity during typical aging

Although aging is associated with changes in brain structure and cognition it remains unclear which specific structural changes mediate individual cognitive changes. Several studies have reported that white matter (WM) integrity, as assessed by diffusion tensor imaging (DTI), mediates, in part, age-related differences in processing speed (PS). There is less evidence for WM integrity mediating age-related differences in higher order abilities (e.g., memory and executive functions). In 165 typically aging adults (age range 54-89) we show that WM integrity in select cerebral regions is associated with higher cognitive abilities and accounts variance not accounted for by PS or age. Specifically, voxel-wise analyses using tract-based spatial statistics (TBSS) revealed that WM integrity was associated with reasoning, cognitive flexibility and PS, but not memory or word fluency, after accounting for age and gender. While cerebral fractional anisotropy (FA) was only associated with PS; mean (MD), axial (AD) and radial (RD) diffusivity were associated with reasoning and flexibility. Reasoning was selectively associated with left prefrontal AD, while cognitive flexibility was associated with MD, AD and RD throughout the cerebrum. Average WM metrics within select WM regions of interest accounted for 18% and 29% of the variance in reasoning and flexibility, respectively, similar to the amount of variance accounted for by age. WM metrics mediated ~50% of the age-related variance in reasoning and flexibility and different proportions, 11% for reasoning and 44% for flexibility, of the variance accounted for by PS. In sum, (i) WM integrity is significantly, but variably, related to specific higher cognitive abilities and can account for a similar proportion of variance as age, and (ii) while FA is selectively associated with PS; while MD, AD and RD are associated with reasoning, flexibility and PS. This illustrates both the anatomical and cognitive selectivity of structure-cognition relationships in the aging brain.

How Interventions Might Improve Cognition in Healthy Older Adults

Many of the cognitive declines in healthy aging are moderated by experience, suggesting that interventions may be beneficial. Goals for aging outcomes include improving performance on untrained tasks, remediating observed cognitive declines, and ensuring preservation of functional ability. This selective review evaluates current progress towards these goals. Most research focuses on untrained tasks. Interventions associated with this outcome include games and exercises practicing specific cognitive skills, as well as aerobic exercise, and modestly benefit a relatively narrow range of cognitive tasks. Few studies have directly tested improvements in tasks on which individuals have been shown to experience longitudinal decline, so this goal has not been realized, though remediation can be examined rather easily. Little work has been done to develop psychometrically strong functional outcomes that could be used to test preservation of independence in everyday activities. Virtual reality approaches to functional assessment show promise for achieving the third goal.

Cohorts based on decade of death: no evidence for secular trends favoring later cohorts in cognitive aging and terminal decline in the AHEAD study

Studies of birth-year cohorts examined over the same age range often report secular trends favoring later-born cohorts, who are cognitively fitter and show less steep cognitive declines than earlier-born cohorts. However, there is initial evidence that those advantages of later-born cohorts do not carry into the last years of life, suggesting that pervasive mortality-related processes minimize differences that were apparent earlier in life. Elaborating this work from an alternative perspective on cohort differences, we compared rates of cognitive aging and terminal decline in episodic memory between cohorts based on the year participants had died, earlier (between 1993 and 1999) or later in historical time (between 2000 and 2010). Specifically, we compared trajectories of cognitive decline in 2 death-year cohorts of participants in the Asset and Health Dynamics Among the Oldest Old study that were matched on age at death and education and controlled for a variety of additional covariates. Results revealed little evidence of secular trends favoring later cohorts. To the contrary, the cohort that died in the 2000s showed a less favorable trajectory of age-related memory decline than the cohort that died in the 1990s. In examinations of change in relation to time to death, the cohort dying in the 2000s experienced even steeper terminal declines than the cohort dying in the 1990s. We suggest that secular increases in "manufacturing" survival may exacerbate age- and mortality-related cognitive declines among the oldest old.

Cohort differences in cognitive aging and terminal decline in the Seattle Longitudinal Study

Life span researchers have long been interested in how and why fundamental aspects of human ontogeny differ between cohorts of people who have lived through different historical epochs. When examined at the same age, later born cohorts are often cognitively and physically fitter than earlier born cohorts. Less is known, however, about cohort differences in the rate of cognitive aging and if, at the very end of life, pervasive mortality-related processes overshadow and minimize cohort differences. We used data on 5 primary mental abilities from the Seattle Longitudinal Study (Schaie, 2005) to compare both age-related and mortality-related changes between earlier born cohorts (1886-1913) and later born cohorts (1914-1948). Our models covary for several individual and cohort differences in central indicators of life expectancy, education, health, and gender. Age-related growth models corroborate and extend earlier findings by documenting level differences at age 70 of up to 0.50 SD and less steep rates of cognitive aging on all abilities between 50 and 80 years of age favoring the later born cohort. In contrast, mortality-related models provide limited support for positive cohort differences. The later born cohort showed steeper mortality-related declines. We discuss possible reasons why often reported positive secular trends in age-related processes may not generalize to the vulnerable segment of the population that is close to death and suggest routes for further inquiry.

Midlife memory improvement predicts preservation of hippocampal volume in old age

This study examines whether midlife change in episodic memory predicts hippocampal volume in old age. From the Seattle Longitudinal Study we retrospectively identified 84 healthy, cognitively normal individuals, age 52 to 87, whose episodic memory had reliably declined (n = 33), improved (n = 28) or remained stable (n = 23) over a 14-year period in midlife (age 43-63). Midlife memory improvement was associated with 13% larger hippocampal volume (p < 0.01) in old age (age 66-87), compared with old age individuals whose midlife episodic memory had either declined or remained stable during midlife. Midlife memory change did not predict total hippocampal volume for those currently in late middle age (age 52-65). The pattern of findings was not modified by gender, apolipoprotein ε4 status, education or current memory performance. Change in midlife memory scores over 14 years, but not any single assessment, predicted hippocampal volumes in old age, emphasizing the importance of longitudinal data in examining brain-cognition relationships. These findings suggest that improvement in memory in midlife is associated with sparing of hippocampal volume in later life.

List and text recall differ in their predictors: replication over samples and time

This study tested the hypothesis that latent list and text recall invoke somewhat different processes. A bivariate outcome path model of latent list and text recall evaluated the effects of age, latent speed, working memory, and vocabulary as their predictors. Independent of age, working memory reliably predicted both recall variables, whereas speed reliably predicted list recall only. The relationship between vocabulary and recall was mediated by age, working memory, and speed. The generalizability of this model, based on data from the 1994 testing of the Long Beach Longitudinal Study, was evaluated across samples by testing its invariance on baseline data from an additional panel and for eventual attrition at baseline and at a subsequent testing of retested participants and dropouts. Results showed that the model was invariant over all groups, supporting a replicable distinction between list and text recall.

A meta-analytic review of emotion recognition and aging: implications for neuropsychological models of aging

This meta-analysis of 28 data sets (N=705 older adults, N=962 younger adults) examined age differences in emotion recognition across four modalities: faces, voices, bodies/contexts, and matching of faces to voices. The results indicate that older adults have increased difficulty recognising at least some of the basic emotions (anger, sadness, fear, disgust, surprise, happiness) in each modality, with some emotions (anger and sadness) and some modalities (face-voice matching) creating particular difficulties. The predominant pattern across all emotions and modalities was of age-related decline with the exception that there was a trend for older adults to be better than young adults at recognising disgusted facial expressions. These age-related changes are examined in the context of three theoretical perspectives-positivity effects, general cognitive decline, and more specific neuropsychological change in the social brain. We argue that the pattern of age-related change observed is most consistent with a neuropsychological model of adult aging stemming from changes in frontal and temporal volume, and/or changes in neurotransmitters.