Subjective cognitive decline (SCD) and subjective olfactory decline (SOD) are frequently reported in the elderly population. SCD and SOD may both predict cognitive decline and dementia onset. However, it is unclear to what extent these complaints co-occur in the general population. If the overlap is high, then SOD might just be a reflection of general cognitive complaints, and SOD could be disregarded. We aimed to describe the occurrence of SOD, SCD and their overlap in individuals from the general population. We used data from a population-based sample in Sweden, aged 35 to 90 years (n=803; 50.9% female). The sample was split into healthy controls, SOD, SCD, and individuals reporting both SOD and SCD. SCD was operationalized based on a single question referring to memory ability. SOD was operationalized based on a single question referring to olfactory ability. We used independent samples t-test to compare the SCD and SOD groups regarding age, sex, education, olfaction and cognitive performance. SOD were present in 21.1% whereas SCD were present in 9.9% of participants. Only 2.7% of participants reported both SOD and SCD. Only 12.9% of SOD reported SCD, whereas 27.5% of those with SCD reported SOD. SOD individuals were significantly older and showed poorer olfactory performance compared to SCD. There were no differences between SCD and SOD regarding sex, education and general cognitive status. SOD often occur independently of SCD in the population, suggesting that they are generally independent risk factors. However, among SCD individuals SOD is relatively common, suggesting that cognitive complaints may involve olfaction. The biological causes underlying SOD and SCD, as well as their risk for future cognitive impairment, needs further investigation.

The research was supported by the Swedish Research Council (2020:00266) to J.K.O.