Association between multimorbidity trajectories and subsequent cognitive decline: evidence from two nationwide...

The number of chronic diseases in a patient may change over time, but how multimorbidity developmental trajectories affect subsequent cognitive decline remains unknown.

Data were drawn from eight waves (2004-2018) of the English Longitudinal Study of Ageing (ELSA) and the Health and Retirement Study (HRS), involving 5300 and 4357 participants, respectively. Group-based trajectory modeling was used to identify multimorbidity trajectories over six years (2004-2010) according to ten chronic diseases. We performed linear mixed-effects models to investigate the association between multimorbidity trajectories and subsequent cognitive decline in global cognition and three cognitive domains, including memory, executive function, and orientation.

Three multimorbidity trajectories (low-stable, moderate-increasing, and rapid-increasing) were identified in two cohorts. Compared to the low-stable trajectory group, the moderate-increasing trajectory group exhibited faster declines in memory [pooled β = -0.027 standard deviation (SD)/year, 95 % confidence interval (CI): -0.044 to -0.011], orientation (pooled β = -0.036 SD/year, 95 % CI: -0.066 to -0.006), and global cognition (pooled β = -0.043 SD/year, 95 % CI: -0.084 to -0.002). Furthermore, the rapid-increasing trajectory group was associated with steeper declines in memory (pooled β = -0.049 SD/year, 95 % CI: -0.084 to -0.015), executive function (pooled β = -0.044 SD/year, 95 % CI: -0.065 to -0.022), orientation (pooled β = -0.077 SD/year, 95 % CI: -0.116 to -0.037), and global cognition (pooled β = -0.138 SD/year, 95 % CI: -0.211 to -0.065).

Limited by the structure of questionnaire, some of the information was derived by self-report, which may lead to recalling bias.

Both moderately and rapidly increased multimorbidity are associated with accelerated cognitive decline among older people. Multimorbidity surveillance and management might help to delay the decline rate of cognition.