Objectives: There is a lack of longitudinal studies, which are both based on nationally representative samples and use standardized instruments to quantify social isolation.Thus, the purpose of this study was to determine the link between perceived social isolation and cognitive functioning longitudinally.Methods/Design: Longitudinal data with n = 6420 from 2014 (wave 5) to 2017 (wave 6) were drawn from the German Ageing Survey (nationally representative sample of individuals aged 40 years and over). Perceived social isolation was assessed using a scale by Bude and Lantermann. Cognitive functioning was quantified using the established digit symbol test. To reduce the problem of unobserved heterogeneity, linear fixed effects regressions were used.Results: Regressions showed that increases in perceived social isolation were associated with decreases in cognitive functioning. With regard to covariates, decreases in cognitive functioning were associated with increases in aging and worsening selfrated health, whereas changes in marital status, employment status, income, physical functioning, and physical illnesses were not associated with the outcome measure.Conclusions: Based on a nationally representative sample and exploiting the panel data structure, the study findings extend current knowledge by showing that increasing perceived social isolation contributes to decreases in cognitive functioning among individuals aged 40 years and over longitudinally. Future longitudinal studies based on panel data methods are required to validate the study findings.
K E Y W O R D Scognition, cognitive functioning, social disconnectedness, social exclusion, social isolation
| INTRODUCTIONIt is widely acknowledged that there is an ongoing change in the demographic structure of industrialized countries, meaning that the number of individuals in late life is increasing continuously. It is also widely understood that age is associated with decreases in cognitive functioning.Moreover, higher age is associated with increased social isolation. 1 Cognitive functioning 2 and social isolation 3 are both associated with subsequent morbidity and mortality, highlighting the importance of these factors.Social isolation is linked to decreased social activities or social engagement, which, in turn, can stimulate cognitive functioning. 4An association between social isolation and cognitive functioning has been demonstrated by recent cross-sectional 5 and longitudinal studies. 6,7 For example, it has been shown that social isolation is related to decreased cognitive function based on data from a Spanish nationally representative sample (n = 1691; individuals ≥50 years; two waves). Similar findings were made by Evans et al based on longitudinal data from the Cognitive Function and