Subjective cognitive and olfactory impairments predict different prospective dementia outcomes

Self-reported measures emerge as potential indicators for early detection of dementia and mortality. We investigated the predictive value of different self-reported measures, including subjective cognitive decline (SCD), subjective olfactory impairment (SOI), subjective taste impairment (STI) and self-reported poor health (SPH), in order to determine the risk of progressing to Alzheimer's Disease (AD) dementia, Parkinson's Disease (PD) dementia or any-other-cause dementia. A total of 6028 cognitively unimpaired individuals from the 8th-wave of the English Longitudinal Study of Ageing (ELSA) were included as baseline sample, and 5297 individuals from the 9th-wave were included as two-year follow-up sample. Self-rated measures were assessed using questions from the ELSA structured interview. Three logistic regression models were fitted to predict different the dementia outcomes. SCD based on memory complaints (OR = 11.145; p < 0.001), and older age (OR = 1.108, p < 0.001) significantly predicted the progression to AD dementia at follow-up. SOI (OR = 7.440; p <0.001) and older age (OR = 1.065, p = 0.035) significantly predicted the progression to PD dementia at follow-up. Furthermore, SCD based on memory complaints (OR = 4.448; p < 0.001) jointly with complaints in other (non-memory) mental abilities (OR = 6.662; p < 0.001), and older age (OR = 1.147, p < 0.001) significantly predicted the progression to dementia of any other cause. Different types of complaints are specifically associated with different dementia outcomes. Our study demonstrates that self-reported measures are a useful and accessible tool when screening for individuals at risk of dementia in the general population.