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To separate age and cohort effects on decline in normal cognitive aging, we applied growth curve models to longitudinal data from the Swedish Adoption/Twin Study of Aging. Data from up to five measurement waves covering a 16-year period were available from 806 participants (age 50 to 88 at the first wave). We divided the sample into two cohorts by birth year: 1900-1925 and 1926-1948. We generated components to tap four cognitive domains: verbal and spatial ability, memory, and speed. We tested cohort differences by using two growth models: quadratic and two linear slopes. Results indicated significant cohort differences in average performance at age 67.5 for all components except speed. When we compared linear slopes during the same age range (age 62- 78), we found no cohort differences. Trajectories of change with age in these four domains were fundamentally the same in middle-old age for individuals born during the first half of the 20th century. [ABSTRACT FROM AUTHOR]

Objectives. The purpose of this study was (a) to investigate whether attrition due to death and nonresponse leads to bias in estimated growth-decline trajectories when only complete data are used in longitudinal research, and (b) to examine the extent of the bias and possible solutions. Methods. The study sample was a subset of the Longitudinal Study of Generations and included data from 208 G1-G2 parent-child dyads and 538 G2-G3 dyads over 30 years. We used a latent growth-decline curve model based on full information maximum likelihood estimation in order to compare parents' and adult children's reports on older respondents' health and intergenerational solidarity by parents' attrition status. Results. Results indicated that attrition due to mortality biased estimates of respondents' assessments of their functional health status over time, and parents' perceptions of the quality of the parent-child relationship deteriorated more rapidly among those who died by Time 7, but nonresponse did not seriously bias estimates of these measures. Using proxies, we found that functional impairment increased more rapidly when children reported about parents, especially in advanced old age. Discussion. These results support the use of full information in estimating growth curves where mortality is present but raise concerns when using child proxies to evaluate parental health or the quality of intergenerational relationships. [ABSTRACT FROM AUTHOR]

Vocabulary knowledge may not be a unidimensional construct, and the relations between vocabulary knowledge and age may depend on the aspect of vocabulary knowledge being assessed. In this study, we examined the factor structure of a vocabulary test given to a large nationally representative sample of individuals (N ∼ 20,500). Results indicated that the vocabulary test is not unidimensional but bidimensional, with Basic Vocabulary and Advanced Vocabulary factors. An analysis of age differences indicates that basic vocabulary is highest around the age of 30, with a negative relation to age in late adulthood; in contrast, advanced vocabulary is unrelated to age between ages 35 and 70. Cohort effects may explain some of the differential age trend. [ABSTRACT FROM AUTHOR]

This is an application of new longitudinal structural equation modeling techniques to time-dependent associations of memory and brain structure measurements. There were 225 participants aged 30–80 years at baseline who were measured again after a 7-year interval on both the lateral ventricular size and Wechsler memory score. Multiple regression analyses show nonlinear associations with age but no relationships among longitudinal changes. Mixed-effects latent growth curve analyses and analyses based on latent difference scores indicate that longitudinal changes in both variables are reasonably well described by an exponential or dual change model. Bivariate dynamic structural equation modeling analyses indicate age-lagged changes operate in a coupled-over-time fashion, with the brain measure (lateral ventricular size) as a leading indicator in time of memory (Wechsler memory score) declines. [ABSTRACT FROM AUTHOR]