An Historical Framework for Cohort Differences in Intelligence

New evidence of trends in cognitive function among middle-aged and older adults in China, 2011-2018: an age-period-cohort analysis

BACKGROUND

Increasing evidence from high-income countries suggests the risk of cognitive impairment has been declining recently. However, related studies in China have rarely been done, and the results are inconsistent. We analyze the trends in cognitive function among middle-aged and older adults in China between 2011 and 2018.

METHODS

We used data from four waves of the China Health and Retirement Longitudinal Study (CHARLS), including 48918 individuals aged 45 years and older. Cognitive function was assessed using the CHARLS cognitive measures containing episodic memory, orientation, attention, and visuospatial abilities. The hierarchical age-period-cohort (APC) model was used to quantify the separate age, period, and cohort effects on trends in cognitive function.

RESULTS

The study sample's ages ranged from 45 to 105 years (Mean = 59.2, SD = 9.4). Cognitive function declined with age net of period and cohort effects, an apparent acceleration in the rate of cognitive decline after age 65 was found adjusting for individual characteristics. Although period effects on trends in cognitive function remained stable during the study period, hierarchical APC models demonstrated significant cohort variations. Independent of age and period effects, there was a fluctuating trend across cohorts before 1960 and an overall decline across successive cohorts.

CONCLUSIONS

Our study indicates that the age effect remains the most crucial factor regarding cognitive decline. Moreover, results demonstrate that cohorts living in social upheaval leading to educational deprivation and/or nutritional deficiency in early life may face a higher risk for cognitive deterioration later in life. Such findings indicate that dementia prevention from a life course perspective and cohort-specific strategies are critical to alleviating the future public-health burdens related to cognitive aging. Ongoing attention should be paid to the role of cross-cohort differences in education on cohort trends in cognition in countries like China that are aging rapidly and have a late start in educational expansion compared to other countries. Other factors, such as environmental stimulation, need to be noticed in younger cohorts.

A lifespan psychological perspective on solitude

Solitude occurs from childhood to old age. In this special issue introduction, we offer a lifespan perspective on matters of solitude with the aim to point to pertinent issues in the field. We propose that solitude serves important functions that may vary across different times in life and that solitude needs to be considered in the context in which it occurs. In applying these lifespan developmental notions, we carve out some open questions that will help extend the current knowledge base including a consideration of issues regarding operational definitions of solitude. We also point to methodological challenges such as capturing processes that unfold on different timescales that need to be addressed to advance the field.

Prior test experience confounds longitudinal tracking of adolescent cognitive and motor development

Background

Accurate measurement of trajectories in longitudinal studies, considered the gold standard method for tracking functional growth during adolescence, decline in aging, and change after head injury, is subject to confounding by testing experience.

Methods

We measured change in cognitive and motor abilities over four test sessions (baseline and three annual assessments) in 154 male and 165 female participants (baseline age 12–21 years) from the National Consortium on Alcohol and NeuroDevelopment in Adolescence (NCANDA) study. At each of the four test sessions, these participants were given a test battery using computerized administration and traditional pencil and paper tests that yielded accuracy and speed measures for multiple component cognitive (Abstraction, Attention, Emotion, Episodic memory, Working memory, and General Ability) and motor (Ataxia and Speed) functions. The analysis aim was to dissociate neurodevelopment from testing experience by using an adaptation of the twice-minus-once tested method, which calculated the difference between longitudinal change (comprising developmental plus practice effects) and practice-free initial cross-sectional performance for each consecutive pairs of test sessions. Accordingly, the first set of analyses quantified the effects of learning (i.e., prior test experience) on accuracy and after speed domain scores. Then developmental effects were  determined for each domain for accuracy and speed having removed the measured learning effects.

Results

The greatest gains in performance occurred between the first and second sessions, especially in younger participants, regardless of sex, but practice gains continued to accrue thereafter for several functions. For all 8 accuracy composite scores, the developmental effect after accounting for learning was significant across age and was adequately described by linear fits. The learning-adjusted developmental effects for speed were adequately described by linear fits for Abstraction, Emotion, Episodic Memory, General Ability, and Motor scores, although a nonlinear fit was better for Attention, Working Memory, and Average Speed scores.

Conclusion

Thus, what appeared as accelerated cognitive and motor development was, in most cases, attributable to learning. Recognition of the substantial influence of prior testing experience is critical for accurate characterization of normal development and for developing norms for clinical neuropsychological investigations of conditions affecting the brain.

The Effects of Selective Survival on Black Adults' Cognitive Development

OBJECTIVES

The theory of selective survival suggests that possibly around 70-75 years of age, Blacks may display substantive changes in their pattern of cognitive decline. This study examined the age-graded pattern of cognitive decline within older Blacks by describing a trend that characterizes differences in the change of cognitive decline from ages 51.5 to 95.5, and hypothesized that this age-graded pattern is nonlinear.

METHOD

Utilizing 2 waves of longitudinal data from the Baltimore Study of Black Aging, this study used multilevel modeling to test whether the interaction between age and the 3-year study period (time between waves) had a positive effect on changes in inductive reasoning, declarative memory, working memory, and perceptual speed.

RESULTS

A significant positive interaction between age and wave was found for inductive reasoning, demonstrating an age-grade pattern of change/decline in cognitive pattern for Blacks aged 51.5-95.4. Simple slope probing via the Johnson-Neyman Technique suggested that Black adults ~64 years and younger experienced significant decline in inductive reasoning across study time, whereas for those older than 63.71, the decline was nonsignificant. No significant age-wave interactions were found for declarative memory, working memory, or perceptual speed.

DISCUSSION

Findings suggest a selective survival effect for inductive reasoning ability among Blacks. With decline evident so early, common cognitive intervention programs targeting adults 65+ may come too late for Blacks, signifying the importance and urgency for early health interventions and public policy designed to promote cognitive reserve.

Cognition in Healthy Aging

The study of cognitive change across a life span, both in pathological and healthy samples, has been heavily influenced by developments in cognitive psychology as a theoretical paradigm, neuropsychology and other bio-medical fields; this alongside the increase in new longitudinal and cohort designs, complemented in the last decades by the evaluation of experimental interventions. Here, a review of aging databases was conducted, looking for the most relevant studies carried out on cognitive functioning in healthy older adults. The aim was to review not only longitudinal, cross-sectional or cohort studies, but also by intervention program evaluations. The most important studies, searching for long-term patterns of stability and change of cognitive measures across a life span and in old age, have shown a great range of inter-individual variability in cognitive functioning changes attributed to age. Furthermore, intellectual functioning in healthy individuals seems to decline rather late in life, if ever, as shown in longitudinal studies where age-related decline of cognitive functioning occurs later in life than indicated by cross-sectional studies. The longitudinal evidence and experimental trials have shown the benefits of aerobic physical exercise and an intellectually engaged lifestyle, suggesting that bio-psycho-socioenvironmental factors concurrently with age predict or determine both positive or negative change or stability in cognition in later life.

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.

Comparison of cognitive and physical functioning of Europeans in 2004-05 and 2013

Background

Adult mortality has been postponed over time to increasingly high ages. However, evidence on past and current health trends has been mixed, and little is known about European disability trends.

Methods

In a cross-sectional setting, we compared cognitive and physical functioning in same-aged Europeans aged 50+ between 2004–05 (wave 1; n = 18 757) and 2013 (wave 5 refresher respondents; n = 16 696), sourced from the Survey of Health, Ageing and Retirement in Europe (SHARE).

Results

People in 2013 had better cognitive function compared with same-aged persons in 2004–05, with an average difference of approximately one-third standard deviation. The same level of cognitive function in 2004–05 at age 50 was found in 2013 for people who were 8 years older. There was an improvement in cognitive function in all European regions. Mean grip strength showed an improvement in Northern Europe of 1.00 kg [95% confidence interval (CI) 0.65; 1.35] and in Southern Europe of 1.68 kg (95% CI 1.14; 2.22), whereas a decrease was found in Central Europe (-0.80 kg; 95% CI −1.16; −0.44). We found no overall differences in activities of daily living (ADL), but small improvements in instrumental activities of daily living (IADL) in Northern and Southern Europe, with an improvement in both ADL and IADL from age 70 in Northern Europe.

Conclusions

Our results indicate that later-born Europeans have substantially better cognitive functioning than earlier-born cohorts. For physical functioning, improvements were less clear, but for Northern Europe there was an improvement in ADL and IADL in the oldest age groups.

Sex Similarities and Differences in Intelligence in Children Aged Two to Eight: Analysis of SON-R 2-8 Scores

The aim of this study was to investigate sex similarities and differences in visuospatial and fluid abilities and IQ scores based on those abilities in children aged two to eight. Standardization data from the Snijders-Oomen Nonverbal Intelligence Test for Children aged 2-8 (SON-R 2-8) were used. A representative sample composed of 965 children from the Netherlands and 762 children from Germany was examined. Small but significant mean sex differences favoring girls were observed until age four. At ages six and seven, boys achieved similar cognitive development levels to girls regarding all abilities assessed and outperformed girls on the Mosaics subtest measuring visuospatial cognition. Boys also displayed higher variability rates in performance. The distribution of IQ scores, with the overrepresentation of girls scoring above mean and the overrepresentation of boys scoring below mean in early childhood, altered with age towards parity between the sexes. The results suggest that girls tend to mature earlier with respect to cognitive abilities. During the course of development, however, the differences between girls and boys may become negligible.

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.

Age variations in cohort differences in the United States: Older adults report fewer constraints nowadays than those 18 years ago, but mastery beliefs are diminished among younger adults

Life Span psychological and life course sociological perspectives have long acknowledged that individual functioning is shaped by historical and sociocultural contexts. Secular increases favoring later-born cohorts are widely documented for fluid cognitive performance and well-being (among older adults). However, little is known about secular trends in other key resources of psychosocial function such as perceptions of control and whether historical changes have occurred in young, middle-aged, and older adults alike. To examine these questions, we compared data from two independent national samples of the Midlife in the United States survey obtained 18 years apart (1995/96 vs. 2013/14) and identified case-matched cohorts (per cohort, n = 2,223, aged = 23-75 years) based on age and gender. We additionally examined the role of economic resources for cohort differences in perceived mastery and constraints. Results revealed that older adults in later-born cohorts reported perceiving fewer constraints than did matched controls 18 years ago, with such positive secular trends being particularly pronounced among women. In contrast, younger adults reported perceiving more constraints in later-born cohorts than those 18 years ago and also reported perceiving lower mastery. We conclude from our national U.S. sample that secular trends generalize to central psychosocial resources across adulthood, such as perceptions of control, but are not unanimously positive. We discuss possible underlying mechanisms and practical implications. (PsycINFO Database Record

Dynamic Patterns of Brain Structure-Behavior Correlation Across the Lifespan

Although the brain/behavior correlation is one of the premises of cognitive neuroscience, there is still no consensus about the relationship between brain measures and cognitive function, and only little is known about the effect of age on this relationship. We investigated the age-associated variations on the spatial patterns of cortical thickness correlates of four cognitive domains. We showed that the spatial distribution of the cortical thickness correlates of each cognitive domain is distinctive and depicts varying age-association differences across the adult lifespan. Specifically, the present study provides evidence that distinct cognitive domains are associated with unique structural patterns in three adulthood periods: Early, middle, and late adulthood. These findings suggest a dynamic interaction between multiple neural substrates supporting each cognitive domain across the adult lifespan.

Decreasing prevalence of dementia in 85-year olds examined 22 years apart: the influence of education and stroke

Individuals aged 80 years and older constitute the fastest growing segment of the population worldwide, leading to an expected increase in dementia cases. Education level and treatment of vascular risk factors has increased during the last decades. We examined whether this has influenced the prevalence of dementia according to DSM-III-R using population-based samples of 85-year-olds (N = 1065) examined with identical methods 1986–87 and 2008–10. The prevalence of dementia was 29.8% in 1986–87 and 21.7% in 2008–10 (OR 0.66; 95%-CI: 0.50–0.86). The decline was mainly observed for vascular dementia. The proportion with more than basic education (25.2% and 57.7%), and the prevalence of stroke (20% and 30%) increased, but the odds ratio for dementia with stroke decreased from 4.3 to 1.8 (interaction stroke*birth cohort; p = 0.008). In a logistic regression, education (OR 0.70; 95%-CI 0.51–0.96), stroke (OR 3.78; 95%-CI 2.28–6.29), interaction stroke*birth cohort (OR 0.50; 95%-CI 0.26–0.97), but not birth cohort (OR 0.98; 95%-CI 0.68–1.41), were related to prevalence of dementia. Thus, the decline in dementia prevalence was mainly explained by higher education and lower odds for dementia with stroke in later born birth cohorts. The findings may be related to an increased cognitive reserve and better treatment of stroke in later-born cohorts.

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.

Modeling Self-Regulation as a Process Using a Multiple Time-Scale Multiphase Latent Basis Growth Model

Measurement burst designs, wherein individuals are measured intensively during multiple periods (i.e., 'bursts'), have created new opportunities for studying change at multiple time-scales. This paper develops a model that may be useful in situations where the functional form of short-term change is unknown, may consist of multiple phases, and may change over the long-term. Specifically, we combine measurement of intraindividual entropy, a latent basis growth model, a multiphase growth model, and a growth model with covariates into a unified framework that may help accommodate the complexity of patterns that emerge in multiple time-scale categorical data streams. Empirical data from a longitudinal study of young children's behavior during laboratory tasks designed to induce frustration are used to illustrate the utility of the proposed model for simultaneously describing intratask (short-term) change in self-regulation and developmental (long-term) shifts in intratask change.

A two decade dementia incidence comparison from the Cognitive Function and Ageing Studies I and II

Dramatic global increases in future numbers of people with dementia have been predicted. No multicentre population-based study powered to detect changes over time has reported dementia incidence. MRC Cognitive Function and Ageing Study (CFAS) undertook baseline interviews in populations aged 65+ years in England and Wales (1989–1994). Three areas (CFAS I) were selected for new sampling two decades later (2008–2011) with same geographical boundaries, sampling and approach methods (CFAS II). At 2 years CFAS I interviewed 5,156 (76% response) with 5,288 interviewed in CFAS II (74% response). Here we report a 20% drop in incidence (95% CI: 0–40%), driven by a reduction in men across all ages above 65. In the UK we estimate 209,600 new dementia cases per year. This study was uniquely designed to test for differences across geography and time. A reduction of age-specific incidence means that the numbers of people estimated to develop dementia in any year has remained relatively stable.

Future dramatic rises in dementia are widely reported, assuming no change in incidence. Matthews and colleagues report that, in contrast to such statements, age-specific incidence has dropped over 20 years, with overall incidence of dementia remaining stable in a large multi-site population study from England.

Cohort Differences in Psychosocial Function over 20 Years: Current Older Adults Feel Less Lonely and Less Dependent on External Circumstances

BACKGROUND

Lifespan psychological and life course sociological perspectives indicate that individual development is shaped by social and historical circumstances. Increases in fluid cognitive performance over the last century are well documented and researchers have begun examining historical trends in personality and subjective well-being in old age. Relatively less is known about secular changes in other key components of psychosocial function among older adults.

OBJECTIVE

In the present study, we examined cohort differences in key components of psychosocial function, including subjective age, control beliefs, and perceived social integration, as indicated by loneliness and availability of very close others.

METHODS

We compared data obtained 20 years apart in the Berlin Aging Study (in 1990-1993) and the Berlin Aging Study II (in 2013-2014) and identified case-matched cohort groups based on age, gender, cohort-normed education, and marital or partner status (n = 153 in each cohort, mean age = 75 years). In follow-up analyses, we controlled for having lived in former East versus West Germany, physical diseases, cohort-normed household income, cognitive performance, and the presence of a religious affiliation.

RESULTS

Consistently across analyses, we found that, relative to the earlier-born BASE cohort (year of birth: mean = 1916; SD = 3.38 years; range = 1901-1922), participants in the BASE-II sample (year of birth: mean = 1939; SD = 3.22 years; range = 1925-1949) reported lower levels of external control beliefs (d = -1.01) and loneliness (d = -0.63). Cohorts did not differ in subjective age, availability of very close others, and internal control beliefs.

CONCLUSION

Taken together, our findings suggest that some aspects of psychosocial function of older adults have improved across the two recent decades. We discuss the possible role of sociocultural factors that might have led to the observed set of cohort differences.

Dementias

This chapter will focus on the descriptive, analytic, and intervention-oriented epidemiology of dementia and its most frequent etiologic type due to Alzheimer's disease. The chapter opens with a brief presentation of the concept of dementia, followed by the presentation of dementia of the Alzheimer type (DAT), including natural history, clinical manifestation, neuropathology, medical prognosis, and management. Further, the chapter presents the prevalence and incidence of dementia, with special consideration of secular trends in prevalence and incidence of DAT, and prognosis of the socioeconomic impact of dementia. Thereafter the main risk factors for DAT are covered. The chapter also addresses the results of ongoing therapeutic and preventive intervention trials for DAT. Finally, the future challenges of the epidemiology of dementia with a focus on the impact of the new diagnostic criteria for neurocognitive disorders, as well as the development of biomarkers for DAT and other types of dementia, will be briefly discussed.

Effects of education and race on cognitive decline: An integrative study of generalizability versus study-specific results

The objective of the study was to examine variability across multiple prospective cohort studies in level and rate of cognitive decline by race/ethnicity and years of education. We compare data across studies, we harmonized estimates of common latent factors representing overall or general cognitive performance, memory, and executive function derived from the: (a) Washington Heights, Hamilton Heights, Inwood Columbia Aging Project (N = 4,115), (b) Spanish and English Neuropsychological Assessment Scales (N = 525), (c) Duke Memory, Health, and Aging study (N = 578), and (d) Neurocognitive Outcomes of Depression in the Elderly (N = 585). We modeled cognitive change over age for cognitive outcomes by race, education, and study. We adjusted models for sex, dementia status, and study-specific characteristics. The results found that for baseline levels of overall cognitive performance, memory, and executive function, differences in race and education tended to be larger than between-study differences and consistent across studies. This pattern did not hold for rate of cognitive decline: effects of education and race/ethnicity on cognitive change were not consistently observed across studies, and when present were small, with racial/ethnic minorities and those with lower education declining at faster rates. In this diverse set of datasets, non-Hispanic Whites and those with higher education had substantially higher baseline cognitive test scores. However, differences in the rate of cognitive decline by race/ethnicity and education did not follow this pattern. This study suggests that baseline test scores and longitudinal change have different determinants, and future studies to examine similarities and differences of causes of cognitive decline in racially/ethnically and educationally diverse older groups is needed.

Historical improvements in well-being do not hold in late life: Birth- and death-year cohorts in the United States and Germany

One key objective of life span research is to examine how individual development is shaped by the historical time people live in. Secular trends favoring later-born cohorts on fluid cognitive abilities have been widely documented, but findings are mixed for well-being. It remains an open question whether secular increases in well-being seen in earlier phases of life also manifest in the last years of life. To examine this possibility, we made use of longitudinal data obtained from the mid-1980s until the late 2000s in 2 large national samples in the United States (Health and Retirement Study [HRS]) and Germany (German Socio-Economic Panel [SOEP]). We operationally defined historical time from 2 complementary perspectives: birth-year cohorts based on the years in which people were born (earlier: 1930s vs. later: 1940s) and death-year cohorts based on the years in which people died (earlier: 1990s vs. later: 2000s). To control for relevant covariates, we used case-matched groups based on age (at death) and education and covaried for gender, health, and number of observations. Results from both countries revealed that well-being in old age was indeed developing at higher levels among later-born cohorts. However, for later-deceased cohorts, no evidence for secular increases in well-being was found. To the contrary, later-dying SOEP participants reported lower levels of well-being at age 75 and 2 years prior to death and experienced steeper late-life declines. Our results suggest that secular increases in well-being observed in old age do not manifest in late life, where "manufactured" survival may be exacerbating age- and mortality-related declines.

Measurement equivalence of the CES-D 8 depression-scale among the ageing population in eleven European countries

Depression is one of the most prevalent mental disorders in later life. However, despite considerable research attention, great confusion remains regarding the association between ageing and depression. There is doubt as to whether a depression scale performs identically for different age groups and countries. Although measurement equivalence is a crucial prerequisite for valid comparisons across age groups and countries, it has not been established for the eight-item version of the Centre for Epidemiological Studies Depression Scale (CES-D8). Using multi-group confirmatory factor analysis, we assess configural, metric, and scalar measurement equivalence across two age groups (50-64 years of age and 65 or older) in eleven European countries, employing data from the Survey of Health, Ageing, and Retirement (SHARE). Results indicate that the construct of depression is comparable across age and country groups, allowing the substantive interpretation of correlates and mean levels of depressive symptoms.

Assessing the Flynn Effect in the Wechsler Scales

The current study examined the Flynn Effect (i.e., the increase in IQ scores over time) across all editions of the Wechsler Adult Intelligence Scale (WAIS), Wechsler Intelligence Scale for Children (WISC), and Wechsler Preschool and Primary Scale of Intelligence (WPPSI). By reverse engineering the correlation and scale score transformations from each Wechsler edition’s technical manual, we made a mean and covariance matrix using the subtests and age groups that were in common for all editions of a given instrument. The results indicated that when aggregated, there was a FE of 0.44 IQ points/year. This Wechsler instrument used, however, moderates the FE, with the WISC showing the largest FE (0.73 IQ points/year) and the WAIS showing a smallest FE (0.30 IQ points/year). Moreover, this study found that the amount of invariant indicators across instruments and age groups varied substantially, ranging from 51.53% in the WISC for the 7-year-old group to 10.00% in the WPPSI for the 5- and 5.5-year-old age groups. Last, we discuss future direction for FE research based on these results.

Cohort effects in age-associated cognitive trajectories

BACKGROUND

The age-specific prevalence and incidence of dementia and cognitive impairment in the United States have either remained stable or even slightly declined during the 1980s-1990s. A suggested but untested reason for this improvement in cognitive function over time is higher educational attainment among more recent cohorts.

METHODS

We used data from two large prospective population-based epidemiological dementia studies conducted in two adjacent regions during the period 1987-2012. We examined whether (i) cohort effects could be observed in age-associated trajectories of cognitive functions and (ii) the observed cohort effects could be explained by educational attainment. Trajectories of neuropsychological tests tapping three domains (psychomotor speed, executive function, and language) were compared among cohorts born between 1902 and 1911, 1912 and 1921, 1922 and 1931, and 1932 and 1943. We examined Age × Cohort interactions in mixed-effects models with/without controlling for education effects.

RESULTS

Cohort effects in age-associated trajectories were observed in all three domains, with consistent differences between the earliest born cohort and the most recent cohort. Executive functions showed the strongest and persistent differences between the most recent and other three cohorts. Education did not attenuate any of these associations.

CONCLUSIONS

Cohort effects were observed in all examined cognitive domains and, surprisingly, remained significant after controlling for educational effects. Factors other than education are likely responsible for the cohort effects in cognitive decline.

Does cognitive function increase over time in the healthy elderly?

BACKGROUND

In dementia screening, most studies have focused on early cognitive impairment by comparing patients suffering from mild dementia or mild cognitive impairment with normal subjects. Few studies have focused on modifications over time of the cognitive function in the healthy elderly. The objective of the present study was to analyze the cognitive function changes of two different samples, born > 15 years apart.

METHOD

A first sample of 204 cognitively normal participants was recruited in the memory clinic of Broca hospital between 1991 and 1997. A second sample of 177 cognitively normal participants was recruited in 2008-2009 in the same institution. Both samples were from the same districts of Paris and were assessed with the same neuropsychological test battery. Mean cognitive test scores were compared between 1991 and 2008 samples, between < 80 years old and ≥ 80 years old in 1991 and 2008 samples, and finally between subjects < 80 year old of 1991 sample and subjects ≥ 80 years old of the 2008 sample. Means were compared with T-tests stratified on gender, age-groups and educational level.

RESULTS

Cognitive scores were significantly higher in the 2008 sample. Participants < 80 years old outperformed those ≥ 80 in both samples. However, participants < 80 years old in 1991 sample and subjects ≥ 80 in the 2008 sample, born on average in 1923, performed mostly identically.

CONCLUSION

This study showed a significant increase of cognitive scores over time. Further, contemporary octogenarians in the later sample performed like septuagenarians in the former sample. These findings might be consistent with the increase in life expectancy and life span in good health. The study highlights the necessity to take into account factors which may contaminate and artificially inflate the age-related differences in favor of younger to the older adults.

Physical and cognitive functioning of people older than 90 years: a comparison of two Danish cohorts born 10 years apart

BACKGROUND

A rapidly increasing proportion of people in high-income countries are surviving into their tenth decade. Concern is widespread that the basis for this development is the survival of frail and disabled elderly people into very old age. To investigate this issue, we compared the cognitive and physical functioning of two cohorts of Danish nonagenarians, born 10 years apart.

METHODS

People in the first cohort were born in 1905 and assessed at age 93 years (n=2262); those in the second cohort were born in 1915 and assessed at age 95 years (n=1584). All cohort members were eligible irrespective of type of residence. Both cohorts were assessed by surveys that used the same design and assessment instrument, and had almost identical response rates (63%). Cognitive functioning was assessed by mini-mental state examination and a composite of five cognitive tests that are sensitive to age-related changes. Physical functioning was assessed by an activities of daily living score and by physical performance tests (grip strength, chair stand, and gait speed).

FINDINGS

The chance of surviving from birth to age 93 years was 28% higher in the 1915 cohort than in the 1905 cohort (6·50% vs 5·06%), and the chance of reaching 95 years was 32% higher in 1915 cohort (3·93% vs 2·98%). The 1915 cohort scored significantly better on the mini-mental state examination than did the 1905 cohort (22·8 [SD 5·6] vs 21·4 [6·0]; p<0·0001), with a substantially higher proportion of participants obtaining maximum scores (28-30 points; 277 [23%] vs 235 [13%]; p<0·0001). Similarly, the cognitive composite score was significantly better in the 1915 than in the 1905 cohort (0·49 [SD 3·6] vs 0·01 [SD 3·6]; p=0·0003). The cohorts did not differ consistently in the physical performance tests, but the 1915 cohort had significantly better activities of daily living scores than did the 1905 cohort (2·0 [SD 0·8] vs 1·8 [0·7]; p<0·0001).

INTERPRETATION

Despite being 2 years older at assessment, the 1915 cohort scored significantly better than the 1905 cohort on both the cognitive tests and the activities of daily living score, which suggests that more people are living to older ages with better overall functioning.

FUNDING

Danish National Research Foundation; US National Institutes of Health-National Institute on Aging; Danish Agency for Science, Technology and Innovation; VELUX Foundation.

Entwicklungsdiagnostik im Alter

Im Rahmen der Entwicklungsdiagnostik im Alter wird gezeigt, wie man unauffällige kognitive Leistungen von pathologischen Abbauprozessen unterscheiden kann. Dies geschieht mit dem regressionsbasierten Normierungsansatz nach Zachary und Gorsuch (1985) . Die Analysen basieren auf Daten einer Multicenter-Studie von N = 349 älteren gesunden Probanden zwischen 60 und 90 Jahren, die mit dem SKT nach Erzigkeit (1989) , einem Leistungstest zur Erfassung von Gedächtnis- und Aufmerksamkeitsstörungen, und zwei Untertests aus der WAIS-IV ( Petermann, 2012 ), dem Matrizentest (MT) und dem Wortschatz-Test (WT) getestet wurden. Es zeigten sich sowohl für den MT als auch den WT signifikante Mittelwertsunterschiede in Abhängigkeit vom Alter, die einen signifikanten Abbau der intellektuellen Fähigkeiten dokumentieren. Die kognitiven Leistungen im Alter hingen signifikant mit der Verarbeitungsgeschwindigkeit sowie wenn auch weniger stark ausgeprägt, mit der Gedächtnisleistung zusammen. Die Ergebnisse des regressionsnormierten Ansatzes scheinen einen bedeutsamen Beitrag zur Entwicklungsdiagnostik im Alter leisten zu können.

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.

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.

Examining the influence of gender, education, social class and birth cohort on MMSE tracking over time: a population-based prospective cohort study

Background

Whilst many studies have analysed predictors of longitudinal cognitive decline, few have described their impact on population distributions of cognition by age cohort. The aim of this paper was to examine whether gender, education, social class and birth cohort affect how mean population cognition changes with age.

Methods

The Medical Research Council Cognitive Function and Ageing Study (MRC CFAS) is a multi-centre population based longitudinal study of 13,004 individuals in England and Wales. Using ten years of follow-up data, mean Mini-mental State Examination (MMSE) scores were modelled by age and birth cohort adjusting for non-random drop-out. The model included terms to estimate cohort effects. Results are presented for five year age bands between 65–95 years.

Results

At a population level, women show greater change in MMSE scores with age than men. Populations with lower education level and manual work also show similar effects. More recent birth cohorts have slightly higher scores.

Conclusion

Longitudinal data can allow examination of population patterns by gender, educational level, social class and cohort. Each of these major socio-demographic factors shows some effect on whole population change in MMSE with age.

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.

Conceptual and measurement challenges in research on cognitive reserve

Cognitive reserve, broadly conceived, encompasses aspects of brain structure and function that optimize individual performance in the presence of injury or pathology. Reserve is defined as a feature of brain structure and/or function that modifies the relationship between injury or pathology and performance on neuropsychological tasks or clinical outcomes. Reserve is challenging to study for two reasons. The first is: reserve is a hypothetical construct, and direct measures of reserve are not available. Proxy variables and latent variable models are used to attempt to operationalize reserve. The second is: in vivo measures of neuronal pathology are not widely available. It is challenging to develop and test models involving a risk factor (injury or pathology), a moderator (reserve) and an outcome (performance or clinical status) when neither the risk factor nor the moderator are measured directly. We discuss approaches for quantifying reserve with latent variable models, with emphasis on their application in the analysis of data from observational studies. Increasingly latent variable models are used to generate composites of cognitive reserve based on multiple proxies. We review the theoretical and ontological status of latent variable modeling approaches to cognitive reserve, and suggest research strategies for advancing the field.

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.

Secular changes in cognitive predictors of dementia and mortality in 70-year-olds

BACKGROUND

Successive elderly birth cohorts improved in cognitive performance during the 20th century. It is not clear whether this influences cognitive predictors of dementia and mortality.

OBJECTIVE

In 2 longitudinal population studies, representing 2 cohorts of 70-year-olds examined 30 years apart, we investigated the relation between baseline cognitive function and 5-year occurrence of dementia and mortality.

METHODS

Two representative cohorts of 70-year-olds initially free from dementia born in 1901-1902 (cohort 1901-1902: n = 381) and 1930 (cohort 1930: n = 551) from Gothenburg, Sweden, were examined in 1971-1972 and 2000-2001 and after 5 years for the outcome of dementia and death. Recent memory was evaluated during psychiatric examinations, and nonmemory domains using psychometric tests.

RESULTS

At age 70, cohort 1930 performed better on psychometric tests, and had fewer recent memory problems compared to cohort 1901-1902. During 5-year follow-up, 5.0% in cohort 1901-1902 and 4.4% in cohort 1930 (p = 0.742) developed dementia, and 15.7% in cohort 1901-1902 and 4.4% in cohort 1930 died (p < 0.001). Recent memory was associated with incident dementia in both cohorts. Low scores in nonmemory tests were associated with incident dementia in cohort 1901-1902, but not in cohort 1930. Recent memory problems and lower scores in nonmemory tests were associated with 5-year mortality in cohort 1901-1902, but not in cohort 1930.

CONCLUSIONS

Secular changes in cognitive performance may influence cognitive predictors of dementia and mortality, despite similar incidence of dementia. The findings should be taken cautiously due to differences between cohorts in refusal rates, quality of education, and dementia recognition in medical records.

Aging, brain disease, and reserve: implications for delirium

Cognitive and brain reserve are well studied in the context of age-associated cognitive impairment and dementia. However, there is a paucity of research that examines the role of cognitive or brain reserve in delirium. Indicators (or proxy measures) of cognitive or brain reserve (such as brain size, education, and activities) pose challenges in the context of the long prodromal phase of Alzheimer disease but are diminished in the context of delirium, which is of acute onset. This article provides a review of original articles on cognitive and brain reserve across many conditions affecting the central nervous system, with a focus on delirium. The authors review current definitions of reserve. The authors identify indicators for reserve used in earlier studies and discuss these indicators in the context of delirium. The authors highlight future research directions to move the field ahead. Reserve may be a potentially modifiable characteristic. Studying the role of reserve in delirium can advance prevention strategies for delirium and may advance knowledge of reserve and its role in aging and neuropsychiatric disease generally.

Increasing levels of semantic verbal fluency in elderly English adults

Analyses incorporating large independent population-based samples and identical measures are needed to investigate recent trends in cognitive function. Nationally representative independent cohorts of community living individuals in England aged 65 years or older from the MRC Cognitive Function and Ageing Study in 1991 (n = 9458) and the English Longitudinal Study of Ageing in 2002 (n = 5196) were compared. East Cambridgeshire participants aged 65-69 years in 1991 (n = 680) were also compared to an independent cohort examined in 1996 (n = 600). Semantic verbal fluency, as measured by the animal naming neuropsychological test, increased by 1.1 extra words a minute in England between 1991 and 2002 (95% CI 0.9, 1.3). A similar increase was also observed in East Cambridgeshire. Levels of semantic verbal fluency appear to have increased in the older English population, which may help to buffer the aging population from future increases in dementia.