Mogle J, Hill NL, Bell TR, Bhargava S, Bratlee-Whitaker E. The factor structure of items assessing subjective memory: between persons and within-persons across time. Gerontology. 2021 Jan;67(3):357-64. doi: 10.1159/000513728

INTRODUCTION: Current understanding of the psychometric properties of items intended to assess the multidimensional construct of subjective memory (SM) is limited, as longitudinal studies of aging commonly use single items or brief sets of items to assess SM. Investigating how SM items cluster within individuals over time would increase the understanding of how combining these items impacts their utility as an early indicator of cognitive change in the aging trajectory. To address this need, the current study examined the factor structure of a brief set of SM items in an existing longitudinal study focused on cognitive aging at both the within-person and between-person levels.

METHODS: Data were drawn from the Einstein Aging Study, a longitudinal cohort study of aging (N = 1,239, Mage = 77.51, SD = 5.03; 69.50% white; 24.27% black; 6.23% other). Community-dwelling older adults from an urban area of New York City were interviewed annually. At each wave, participants responded to 6 items intended to assess SM. Items assessed participants' perceived memory decline as well as current memory ability. Multilevel exploratory factor analyses examined which factor solution best fit the data at between-person and within-person levels.

RESULTS: Factor structure of the SM items varied at the two levels. At the within-person level, two factors emerged, whereas at the between-person level, a single factor best represented the SM items. Items assessing perceived declines in memory functioning tended to have similar trajectories, while items assessing current memory ability were less related to change over time.

CONCLUSION: Items appeared to assess two different dimensions of SM when examining within-person changes in SM across time; however, the item structure suggested no other items covaried systematically within persons over time. In contrast to the conceptualization of SM as a multidimensional construct, our findings suggest that when measuring SM between individuals, SM items tend to capture a single dimension underlying SM. This may be due to the long retrospection period of items assessing perceived memory ability. A single item assessing perceived memory decline in older adults without evidence of objective cognitive impairment may be sufficient to monitor memory change in clinical or research settings.

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