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INTRODUCTION: We aimed to investigate mid-life food insecurity over time in relation to subsequent memory function and rate of decline in Agincourt, rural South Africa. METHODS: Data from the longitudinal Agincourt Health and Socio-Demographic Surveillance System (Agincourt HDSS) were linked to the population-representative Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa (HAALSI). Food insecurity (yes vs. no) and food insecurity intensity (never/rarely/sometimes vs. often/very often) in the past month were assessed every 3 years from 2004 to 2013 in Agincourt HDSS. Cumulative exposure to each food insecurity measure was operationalized as 0, 1, and ≥2 time points. Episodic memory was assessed from 2014/15 to 2021/22 in HAALSI. Mixed-effects linear regression models were fitted to investigate the associations of each food insecurity measure with memory function and rate of decline over time. RESULTS: A total of 3,186 participants (mean age [SD] in 2004: 53 [12.87]; range: 30-96) were included and 1,173 (36%) participants experienced food insecurity in 2004, while this figure decreased to 490 (15%) in 2007, 489 (15%) in 2010, and 150 (5%) in 2013. Experiencing food insecurity at one time point (vs. never) from 2004 to 2013 was associated with lower baseline memory function (ß = -0.095; 95% CI: -0.159 to -0.032) in 2014/15 but not rate of memory decline. Higher intensity of food insecurity at ≥2 time points (vs. never) was associated with lower baseline memory function (ß = -0.154, 95% CI: -0.338 to 0.028), although the estimate was imprecise. Other frequencies of food insecurity and food insecurity intensity were not associated with memory function or decline in the fully adjusted models. CONCLUSION: In this setting, mid-life food insecurity may be a risk factor for lower later-life memory function, but not decline.
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INTRODUCTION: Despite rapid population aging, there are currently limited data on the incidence of aging-related cognitive impairment in sub-Saharan Africa. We aimed to determine the incidence of cognitive impairment and its distribution across key demographic, social, and health-related factors among older adults in rural South Africa. METHODS: Data were from in-person interviews with 3,856 adults aged ≥40 who were free from cognitive impairment at baseline in the population-representative cohort, "Health and Aging in Africa: a Longitudinal Study of an INDEPTH Community in South Africa" (HAALSI), in Agincourt sub-district, Mpumalanga province, South Africa (2014-19). Cognitive impairment was defined as scoring <1.5 standard deviations below the mean of the baseline distribution of orientation and episodic memory scores. Incidence rates and rate ratios for cognitive impairment were estimated according to key demographic, social, and health-related factors, adjusted for age, sex/gender, and country of birth. RESULTS: The incidence of cognitive impairment was 25.7/1,000 person-years (PY; 95% confidence interval [CI]: 23.0-28.8), weighted for mortality (12%) and attrition (6%) over the 3.5-year mean follow-up (range: 1.5-4.8 years). Incidence increased with age, from 8.9/1,000 PY (95% CI: 5.2-16.8) among those aged 40-44 to 93.5/1,000 PY (95% CI: 75.9-116.3) among those aged 80+, and age-specific risks were similar by sex/gender. Incidence was strongly associated with formal education and literacy, as well as marital status, household assets, employment, and alcohol consumption but not with history of smoking, hypertension, stroke, angina, heart attack, diabetes, or prevalent HIV. CONCLUSIONS: This study presents some of the first incidence rate estimates for aging-related cognitive impairment in rural South Africa. Social disparities in incident cognitive impairment rates were apparent in patterns similar to those observed in many high-income countries.
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Envelhecimento , Disfunção Cognitiva , Idoso , Disfunção Cognitiva/epidemiologia , Humanos , Incidência , Estudos Longitudinais , População Rural , África do Sul/epidemiologiaRESUMO
AIM: To investigate mid-life employment trajectories in relation to later-life memory function and rate of decline in rural South Africa. METHODS: Data from the Agincourt Health and Socio-Demographic Surveillance System were linked to the 'Health and Ageing in Africa: A Longitudinal Study of an INDEPTH Community in South Africa' (HAALSI) in rural Agincourt, South Africa (N = 3133). Employment was assessed every 4 years over 2000-12 as being employed (0, 1, 2 and ≥3 time points), being employed in a higher-skill occupation (0, 1, 2 and ≥3 time points) and dynamic employment trajectories identified using sequence analysis. Latent memory z-scores were assessed over 2014-22. Mixed-effects linear regression models were fitted to examine the associations of interest. RESULTS: Sustained mid-life employment from 2000-12 (ß = 0.052, 95% CI: -0.028 to 0.132, 1 vs 0 time points; ß = 0.163, 95% CI: 0.077 to 0.250, 2 vs 0 time points; ß = 0.212, 95% CI: 0.128 to 0.296, ≥3 vs 0 time points) and greater time spent in a higher-skill occupation (ß = 0.077, 95% CI: -0.020 to 0.175, 1 vs 0 time points; ß = 0.241, 95% CI: 0.070 to 0.412, 2 vs 0 time points; ß = 0.361, 95% CI: 0.201 to 0.520, ≥3 vs 0 time points) were associated with higher memory scores in 2014/15, but not subsequent rate of memory decline. Moving from a lower-skill to higher-skill occupation was associated with higher memory function, but a faster rate of decline over 2014-22. CONCLUSIONS: Sustained mid-life employment, particularly in higher-skill occupations, may contribute to later-life memory function in this post-Apartheid South African setting.
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Envelhecimento , Cognição , Humanos , África do Sul/epidemiologia , Estudos Longitudinais , Emprego , População RuralRESUMO
BACKGROUND AND PURPOSE: Brain arterial diameters are markers of cerebrovascular disease. Demographic and anatomical factors may influence arterial diameters. We hypothesize that age, sex, height, total cranial volume (TCV), and persistent fetal posterior cerebral artery (fPCA) correlate with brain arterial diameters across populations. METHODS: Participants had a time-of-flight MRA from nine international cohorts. Arterial diameters of the cavernous internal carotid arteries (ICA), middle cerebral arteries (MCA), and basilar artery (BA) were measured using LAVA software. Regression models assessed the association between exposures and brain arterial diameters. RESULTS: We included 6,518 participants (mean age: 70 ± 9 years; 41% men). Unilateral fPCA was present in 13.2% and bilateral in 3.2%. Larger ICA, MCA, and BA diameters correlated with older age (Weighted average [WA] per 10 years: 0.18 mm, 0.11 mm, and 0.12 mm), male sex (WA: 0.24 mm, 0.13 mm, and 0.21 mm), and TCV (WA: for one TCV standard deviation: 0.24 mm, 0.29 mm, and 0.18 mm). Unilateral and bilateral fPCAs showed a positive correlation with ICA diameters (WA: 0.39 mm and 0.73 mm) and negative correlation with BA diameters (WA: -0.88 mm and -1.73 mm). Regression models including age, sex, TCV, and fPCA explained on average 15%, 13%, and 25% of the ICA, MCA, and BA diameter interindividual variation, respectively. Using height instead of TCV as a surrogate of head size decreased the R-squared by 3% on average. CONCLUSION: Brain arterial diameters correlated with age, sex, TCV, and fPCA. These factors should be considered when defining abnormal diameter cutoffs across populations.
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Angiografia por Ressonância Magnética , Humanos , Masculino , Feminino , Idoso , Estudos de Coortes , Fatores Sexuais , Fatores Etários , Pessoa de Meia-Idade , Artéria Carótida Interna/anatomia & histologia , Artéria Carótida Interna/diagnóstico por imagem , Artéria Cerebral Média/diagnóstico por imagem , Artéria Cerebral Média/anatomia & histologia , Encéfalo/diagnóstico por imagem , Encéfalo/anatomia & histologia , Artéria Cerebral Posterior/diagnóstico por imagem , Artéria Cerebral Posterior/anatomia & histologia , Artéria Basilar/diagnóstico por imagem , Artéria Basilar/anatomia & histologia , Idoso de 80 Anos ou mais , Artérias Cerebrais/diagnóstico por imagem , Artérias Cerebrais/anatomia & histologiaRESUMO
Objectives: This study investigates the association between cohort derived dementia and serologically confirmed SARS-CoV-2 infection, an underexplored phenomena in low-and middle-income countries. Examining this relationship in a rural South African community setting offers insights applicable to broader healthcare contexts. Methods: Data were collected from Black South Africans in the Mpumalanga province who participated in the Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa. Cohort derived dementia was developed using a predictive model for consensus-based dementia diagnosis. Multinomial logistic regression models estimated the association between predicted dementia probability in 2018 and SARS-CoV-2 infection risk in 2021, controlling for demographics, socioeconomic status, and comorbidities. Results: Fifty-two percent of the tested participants had serologically confirmed SARS-CoV-2 infections. In the fully adjusted model, cohort derived dementia was significantly associated with over twice the risk of serological diagnosis of COVID-19 (RRR = 2.12, p = 0.045). Conclusion: Complying with COVID-19 prevention recommendations may be difficult for individuals with impaired cognitive functioning due to their symptoms. Results can inform community-based public health initiatives to reduce COVID-19 transmission among South Africa's rapidly aging population.
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COVID-19 , Demência , Adulto , Humanos , Idoso , África do Sul/epidemiologia , Estudos Longitudinais , COVID-19/diagnóstico , COVID-19/epidemiologia , SARS-CoV-2 , Demência/diagnóstico , Demência/epidemiologia , Teste para COVID-19RESUMO
INTRODUCTION: We describe the development and feasibility of using an online consensus approach for diagnosing cognitive impairment and dementia in rural South Africa. METHODS: Cognitive assessments, clinical evaluations, and informant interviews from Cognition and Dementia in the Health and Aging in Africa Longitudinal Study (HAALSI Dementia) were reviewed by an expert panel using a web-based platform to assign a diagnosis of cognitively normal, mild cognitive impairment (MCI), or dementia. RESULTS: Six hundred thirty-five participants were assigned a final diagnostic category, with 298 requiring adjudication conference calls. Overall agreement between each rater's independent diagnosis and final diagnosis (via the portal or consensus conference) was 78.3%. A moderate level of agreement between raters' individual ratings and the final diagnostic outcomes was observed (average κ coefficient = 0.50). DISCUSSION: Findings show initial feasibility in using an online consensus approach for the diagnosis of cognitive impairment and dementia in remote, rural, and low-resource settings.
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Telomere length (TL) may be a biomarker of aging processes as well as age-related diseases. However, most studies of TL and aging are conducted in high-income countries. Less is known in low- and middle-income countries (LMICs) such as South Africa, where life expectancy remains lower despite population aging. We conducted a descriptive analysis of TL in a cohort of older adults in rural South Africa. TL was assayed from venous blood draws using quantitative polymerase chain reaction (T/S ratio). We examined the correlation between TL and biomarkers, demographic characteristics, mental/cognitive health measures, and physical performance measures in a subsample of the Wave 1 2014-2015 "Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa" (HAALSI) cohort (n = 510). We used logistic regression to measure the association between TL and mortality through Wave 3 (2021-2022). In bivariate analyses, TL was significantly correlated with age (r = -0.29, p < .0001), self-reported female sex (r = 0.13, p = .002), mortality (r = -0.1297, p = .003), diastolic blood pressure (r = 0.09, p = .037), pulse pressure (r = -0.09, p = .045), and being a grandparent (r = -0.17, p = .0001). TL was significantly associated with age (ß = -0.003; 95% confidence interval [CI] = -0.005, -0.003). TL was significantly associated in unadjusted multivariate analyses with mortality, but the relationship between TL and mortality was attenuated after adjusting for age (odds ratio [OR] = 0.19; 95% CI = 0.03, 1.27) and other covariates (OR = 0.17; 95% CI = 0.02, 1.19). Our study is the first analysis of TL in an older adult South African population. Our results corroborate existing relationships between TL and age, sex, cardiometabolic disease, and mortality found in higher-income countries.
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Envelhecimento , Expectativa de Vida , Humanos , Feminino , Idoso , Estudos Longitudinais , África do Sul/epidemiologia , Envelhecimento/genética , Biomarcadores , TelômeroRESUMO
We investigate the associations between marital status and cognitive well-being among adults aged 50 and older across four settings: the United States, rural South Africa, Mexico, and China. Using a standardized measure of immediate word recall, we assess whether people in each non-married status have worse cognitive function than their married counterparts, and the extent to which these associations vary across settings. We theorize that the practices around marriage in each setting, as well as the social stigma attached to marital dissolution, will reveal differing associations between marital status and cognition. Results suggest that, among women, being in a widowed marital status is associated with lower cognitive function in each setting except Mexico (after accounting for education and employment), while being separated/divorced or never married is associated with lower cognitive function only among women in the U.S. and Mexico. Among men, being widowed is associated with lower cognitive function relative to being married in each setting except South Africa (after accounting for education and employment), and being never married is associated with lower cognitive function in the U.S. and China (but not in South Africa or Mexico, after accounting for education and employment). Men also face relatively lower cognitive function if separated/divorced in the U.S. and South Africa. We discuss possible reasons for these associations across settings.
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[This corrects the article DOI: 10.3389/fgene.2021.689756.].
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BACKGROUND: The relationship between subjective social position (SSP) and cognitive ageing unclear, especially in low-income settings. We aimed to investigate the relationship between SSP and cognitive function over time among older adults in rural South Africa. METHODS: Data were from 3771 adults aged ≥40 in the population-representative 'Health and Ageing in Africa: A Longitudinal Study of an INDEPTH Community in South Africa' from 2014/2015 (baseline) to 2018/2019 (follow-up). SSP was assessed at baseline with the 10-rung MacArthur Network social position ladder. Outcomes were composite orientation and episodic memory scores at baseline and follow-up (range: 0-24). Mortality- and attrition-weighted linear regression estimated the associations between baseline SSP with cognitive scores at each of the baseline and follow-up. Models were adjusted for age, age2, sex, country of birth, father's occupation, education, employment, household assets, literacy, marital status and health-related covariates. RESULTS: SSP responses ranged from 0 (bottom ladder rung/lowest social position) to 10 (top ladder rung/highest social position), with a mean of 6.6 (SD: 2.3). SSP was positively associated with baseline cognitive score (adjusted ß=0.198 points per ladder rung increase; 95% CI 0.145 to 0.253) and follow-up cognitive score (adjusted ß=0.078 points per ladder rung increase; 95% CI 0.021 to 0.136). CONCLUSION: Independent of objective socioeconomic position measures, SSP is associated with orientation and episodic memory scores over two time points approximately 3 years apart among older rural South Africans. Future research is needed to establish the causality of the observed relationships, whether they persist over longer follow-up periods and their consistency in other populations.
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Cognição , População Rural , Idoso , Envelhecimento/psicologia , Cognição/fisiologia , Humanos , Estudos Longitudinais , África do Sul/epidemiologiaRESUMO
Objectives: We investigate how caregiving for grandchildren is associated with cognitive function among rural South Africans, and whether the association differs by gender. We further investigate whether measures of physical activity or social engagement mediate this association. Methods: Data were from interviews with 3668 Black, South African grandparents in the "Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa" study, conducted between 2014 and 2015. Results: We find that caregiving grandparents have better cognitive function than non-caregiving grandparents, and this association does not differ by grandparent gender. Although grandchild caregiving is associated with physical activity and social engagement measures, and some of these measures are associated with cognitive function, we do not find conclusive evidence of mediation. Discussion: Providing care for grandchildren may stimulate cognitive function for both grandmothers and grandfathers. Neither physical activity nor social engagement explains the association between caregiving and cognitive function.
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Avós , Cognição , Humanos , Relação entre Gerações , Estudos Longitudinais , África do SulRESUMO
Objectives: Our study investigates measurement, correlates, and functional associations of vision impairment (VI) in an aging population in rural South Africa. Methods: 1582 participants aged 40-69 reported on near (NVI) and distance vision impairment (DVI) and completed objective vision tests. Logistic and linear regression were used to evaluate sociodemographic, health, and psychosocial correlates of VI and assess relationships between VI and cognitive and physical function. Results: VI prevalence was considerably higher according to objective testing (56%) versus self-reports (18%). Older adults were especially likely to underreport impairment. Objective VI was associated with age, education, cardiometabolic disease, and female sex. Conversely, self-reported VI was associated with psychosocial factors. Objective NVI and both types of DVI were associated with worse visual cognition and slower gait speed, respectively. Discussion: Self-reported and objective VI measures should not be used interchangeably in this context. Our findings highlight extensive burden of untreated VI in this region.
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Envelhecimento , Cognição , Idoso , Escolaridade , Feminino , Humanos , Autorrelato , Transtornos da Visão/epidemiologia , Testes VisuaisRESUMO
Apolipoprotein E (APOE) ð4 allele carrier status is well known for its association with an increased likelihood of developing Alzheimer's disease, but its independent role in cognitive function is unclear. APOE genetic variation is understudied in African populations; hence, this cross-sectional study in a rural South African community examined allele and genotype frequencies, and their associations with cognitive function. Cognitive function was assessed using two different screening methods to produce a total cognition score and four domain-specific cognition scores for verbal episodic memory, executive function, language, and visuospatial ability. Cognitive phenotype and APOE genotype data were used to determine whether APOE variation was significantly associated with cognitive function in this population. Observed allele frequencies for 1776 participants from the HAALSI study [age 40-80years (mean=56.19); 58.2% female] were 58.1% (ð3), 25.4% (ð4) and 16.5% (ð2). Allele distributions were similar to the African super population, but different from all non-African super populations from the 1,000 Genomes Project. The ð3 homozygous genotype was most common (34.9%) and used as the base genotype for comparison in regression models. Four models were tested for each of the five cognitive phenotypes to explore association of APOE variation with cognitive function. In the first model assessing association with all genotypes for all individuals, marginally significant associations were observed for ð2 homozygotes where executive function scored higher by ~0.5 standard deviations (p=0.037, SE=0.23), and for ð3/ð4 heterozygotes where visuospatial ability scores were lower (p=0.046, SE=0.14). These did not survive correction for multiple testing. Regional African population differences were observed at the APOE locus. Marginally, significant associations between APOE genotype, and executive function and visuospatial ability indicate the need for larger studies to better examine these associations in African populations. Furthermore, longitudinal data could shed light on APOE genetic association with rate of change, or decline, in cognitive function.
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OBJECTIVES: Direction and magnitude of gender differences in late-life cognitive function are inextricably tied to sociocultural context. Our study evaluates education and literacy as primary drivers of gender equality in cognitive performance among middle-aged and older adults in rural South Africa. METHOD: Data were collected on 1,938 participants aged 40-79 from Agincourt, South Africa. Cognitive function was measured via the Oxford Cognitive Screen-Plus, a tablet-based assessment with low literacy demands. Four cognitive domains were derived through confirmatory factor analysis: episodic memory, executive function, visual spatial, and language. Structural equation models tested domain-specific gender effects, incrementally controlling for demographic, education, health, and socioeconomic variables. RESULTS: In the model adjusting only for demographic factors, men outperformed women on executive function and visual-spatial domains. Adding education and literacy to the model revealed a robust female advantage in episodic memory, and reduced the magnitude of male advantage in executive function and visual and spatial by 47% and 42%, respectively. Health and socioeconomic factors did not alter patterns of gender associations in subsequent models. DISCUSSION: In this older South African cohort, gender inequality in cognitive performance was partially attributable to educational differences. Understanding biopsychosocial mechanisms that promote cognitive resilience in older women is critically important given the predominantly female composition of aging populations worldwide.
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Cognição , Escolaridade , Disparidades nos Níveis de Saúde , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , População Rural/estatística & dados numéricos , Fatores Sexuais , Fatores Socioeconômicos , África do Sul/epidemiologiaRESUMO
BACKGROUND: Several theories seek to explain how social connections and cognitive function are interconnected in older age. These include that social interaction protects against cognitive decline, that cognitive decline leads to shedding of social connections and that cognitive decline leads to increased instrumental support. We investigated how patterns of social contact, social support and cognitive health in rural South Africa fit with these three theories. METHOD: We used data from the baseline of "Health and Aging in Africa: a Longitudinal Study of an INDEPTH community in South Africa" (HAALSI), a population-based study of 5059 individuals aged ≥ 40 years. We evaluated how a range of egocentric social connectedness measures varied by respondents' cognitive function. RESULTS: We found that respondents with lower cognitive function had smaller, denser social networks that were more local and more kin-based than their peers. Lower cognitive function was associated with receipt of less social support generally, but this difference was stronger for emotional and informational support than for financial and physical support. Impairment was associated with greater differences among those aged 40-59 and those with any (versus no) educational attainment. CONCLUSIONS: The patterns we found suggest that cognitively impaired older adults in this setting rely on their core social networks for support, and that theories relating to social connectedness and cognitive function developed in higher-income and higher-education settings may also apply in lower-resource settings elsewhere.
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População Rural , Apoio Social , Adulto , Idoso , Cognição , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , África do Sul/epidemiologiaRESUMO
Research on early life adversity and later-life cognitive function is conflicting, with little evidence from low-income settings. We investigated associations between adverse childhood experiences and cognitive function in an older population who grew up under racial segregation during South African apartheid. Data were from 1,871 adults aged 40-79 in the population-representative "Health and Ageing in Africa: A Longitudinal Study of an INDEPTH Community in South Africa" in 2015. The adverse childhood experiences were having a parent unemployed for > 6 months; having parents who argued or fought often; having a parent who drank excessively, used drugs, or had mental health problems; and physical abuse from parents. Executive function, language, visuospatial ability, and memory were assessed with the Oxford Cognitive Screen-Plus, a validated cognitive assessment designed for low-income, low-literacy settings. We estimated associations between adverse childhood experiences and latent cognitive domain z-scores using multiple-indicator, multiple-cause structural equation models. Childhood adversities were reported by 15% (parental unemployment for > 6 months), 25% (parents argued or fought often), 25% (a parent drank excessively, used drugs, or had mental health problems), and 35% (physical abuse from parent) of respondents. They were not associated with cognition, except that having a parent who drank excessively, used drugs, or had mental health problems was associated with lower memory z-scores (-0.07; 95% CI [-0.13, -0.01]). This is one of the first investigations into later-life cognitive outcomes associated with early adversity in a population with a historical context of pervasive trauma, and suggests that later-life memory may be vulnerable to early adversity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
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Experiências Adversas da Infância , Envelhecimento/psicologia , Cognição/fisiologia , População Rural , Adulto , Idoso , Criança , Feminino , Humanos , Alfabetização , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Pais , Vigilância da População , África do Sul/epidemiologiaRESUMO
BACKGROUND: Subjective cognitive decline (SCD) is increasingly considered promising to detect preclinical Alzheimer's disease. How SCD is ascertained is critical for determining its potential utility in identifying at-risk individuals, yet SCD measures differ along several dimensions. OBJECTIVE: We aimed to examine the extent to which reports of SCD in healthy elderly may be influenced by the characteristics of the SCD measures. We investigated variations in rates of SCD endorsement across different measures, including an open-ended question. We also examined the association of responses across measures, and the degree to which specific SCD items were associated with objective memory performance. METHODS: 99 healthy elderly completed a series of questionnaires from which 10 items examining SCD for memory and other aspects of cognition were drawn. We applied Cochran's Q tests to assess differences in rates of SCD, correlation analyses to examine association of SCD responses, and regression models to determine the association between SCD items and delayed verbal memory. RESULTS: Rates of SCD varied as a function of the assessment format, ranging from 1 to 7% for memory and 5 to 20% for concentration. SCD was lower for memory versus non-memory domains. SCD items were associated both within and across domains. The most accurate predictor of memory was memory-related SCD in comparison to others the same age. CONCLUSION: Characteristics of SCD items influence rates of endorsement. Querying SCD using an "age-anchored" question may provide the most accurate reflection of actual cognitive performance.
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Envelhecimento , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/psicologia , Idoso , Idoso de 80 Anos ou mais , Transtornos Cognitivos/complicações , Feminino , Humanos , Masculino , Transtornos da Memória/diagnóstico , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Valores de Referência , Aprendizagem VerbalRESUMO
While previous research has shown that high syllable frequency can facilitate speech production at the level of phonological/phonetic encoding, little is known about its influence on prephonological processes, specifically lexical selection. The current study used a picture-word interference (PWI) task to (a) shed light on the stages of lexical access where syllable frequency is relevant, and (b) inform as to whether lexical selection is accomplished via competition among activated word options. Participants named pictures whose names had high-frequency (HF) and low-frequency (LF) first syllables while ignoring phonologically related (same first syllable) or unrelated distractor words that were presented simultaneously. Word frequency was also manipulated, as half of the targets were HF words, and half were LF words. Results revealed inhibitory syllable frequency effects in all conditions, such that targets with HF first syllables were named more slowly than targets with LF first syllables. However, inhibitory syllable frequency effects were exacerbated in conditions thought to reflect heightened lexical competition, specifically in the presence of phonologically related distractors and for targets with low word frequency. These findings reveal novel evidence for first-syllable frequency effects on lexical selection and offer further support for models proposing delays at lexical selection due to activation of nontarget competitors.
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Comportamento de Escolha , Inibição Psicológica , Fala , Vocabulário , Adolescente , Humanos , Reconhecimento Visual de Modelos , Adulto JovemRESUMO
OBJECTIVE: Clinic-based studies suggest that dementia is diagnosed at older ages in bilinguals compared with monolinguals. The current study sought to test this hypothesis in a large, prospective, community-based study of initially nondemented Hispanic immigrants living in a Spanish-speaking enclave of northern Manhattan. METHOD: Participants included 1,067 participants in the Washington/Hamilton Heights Inwood Columbia Aging Project (WHICAP) who were tested in Spanish and followed at 18-24 month intervals for up to 23 years. Spanish-English bilingualism was estimated via both self-report and an objective measure of English reading level. Multilevel models for change estimated the independent effects of bilingualism on cognitive decline in 4 domains: episodic memory, language, executive function, and speed. Over the course of the study, 282 participants developed dementia. Cox regression was used to estimate the independent effect of bilingualism on dementia conversion. Covariates included country of origin, gender, education, time spent in the United States, recruitment cohort, and age at enrollment. RESULTS: Independent of the covariates, bilingualism was associated with better memory and executive function at baseline. However, bilingualism was not independently associated with rates of cognitive decline or dementia conversion. Results were similar whether bilingualism was measured via self-report or an objective test of reading level. CONCLUSIONS: This study does not support a protective effect of bilingualism on age-related cognitive decline or the development of dementia. In this sample of Hispanic immigrants, bilingualism is related to higher initial scores on cognitive tests and higher educational attainment and may not represent a unique source of cognitive reserve.