Cumulative loneliness and subsequent memory function and rate of decline among adults aged ≥50 in the United States, 1996-2016

Abstract

BackgroundTo investigate the association between the cumulative duration of loneliness and subsequent memory function and rate of decline over a 20-year period in middle aged and older adults.MethodData were from biennial interviews with 9,032 adults aged ≥50 in the population-based US Health and Retirement Study from 1996-2016. Loneliness status (yes vs. no) was assessed biennially from 1996-2004 and its duration over this period was categorized as never, 1 time point, 2 time points, and ≥3 time points. Episodic memory was assessed biennially from 2004-2016 as a composite of immediate and delayed recall trials combined with proxy-reported memory. We used multivariable-adjusted mixed effects regression to estimate the association between loneliness duration and subsequent memory function and decline. Three-way interaction terms were included to test effect modification by sex and age.ResultMean (SD) age at baseline was 64 (9) years, 63% of the sample was female (5,646/9,032), and the median follow-up time was 10 years, contributing 46,890 observations from 2004-2016. A total of 1,624 adults (18%) experienced loneliness at one time point, 825 (9%) experienced loneliness at two time points, and 1,069 (12%) experienced loneliness at ≥3 time points. Annual memory decline among non-lonely adults was 0.08 standard deviation (SD) units (95% CI: -0.08, -0.07) per year. A longer duration of loneliness was associated with a faster rate of memory decline (1 time point: 0.01 SD additional annual decline, 95% CI: -0.01, -0.01; 2 time points: 0.02 SD additional annual decline, 95% CI: -0.02, -0.01; ≥3 time points: 0.03 SD additional annual decline, 95% CI: -0.03, -0.02; P trend <0.001). The association was stronger among women than men (three-way interaction P trend <0.001) and adults aged ≥65 years than those aged <65 years (three-way interaction P trend = 0.01).ConclusionLong-term loneliness may be a salient risk factor for accelerated memory aging, especially among women aged 65 and over. Our findings could help rule out reverse causation between loneliness and memory outcomes, suggesting that loneliness could be part of a preclinical syndrome of Alzheimer’s disease and related dementias.