Longitudinal analysis of the impact of loneliness on cognitive function over a 20-year follow-up.

Background: Loneliness and cognitive impairment are both commonly experienced by older old people, but evidence for the association between these has been inconsistent. Moreover, most evidence has been cross-sectional in nature and largely based on studies with relatively young later life age groups rather than 'the oldest old'. We aimed to test the potential impact of loneliness amongst older old people on their cognitive function over a 20-year period.Method: Data were drawn from wave 3 to wave 10 of the Cambridge City over-75s Cohort (CC75C) study. The impact of loneliness on transition between normal and impaired cognitive states was examined by multi-state modelling. The associations between loneliness changes and cognitive function decline were tested by using generalized estimating equation (GEE) with an independent working correlation structure. Missing data were imputed by using multiple imputation chained equations.Results: At wave 3, 713 participants were interviewed, of whom 657 (92%) had Mini-Mental State Examination (MMSE) assessments. Of individuals who had an MMSE score, approximately one quarter reported feeling lonely, and another 16% felt slightly lonely. The prevalence of feeling lonely or slightly lonely varied between waves. Results from multi-state modelling indicated that loneliness was not related to cognitive function transitions, and results from the GEE model showed that loneliness was not significantly associated with cognitive function decline after adjusting for cohort effects, follow-up time, sex, education, and interaction terms for sex, education and time.Conclusions: Loneliness did not exert long-term harmful effects on cognitive function in the oldest old.