Subjective cognitive decline (SCD), the potentially earliest notable manifestation of preclinical Alzheimer's disease and other dementias, was consistently associated with lower quality of life in cross-sectional studies. The aim of this study was to investigate whether such an association persists longitudinally – particularly with health-related quality of life (HRQoL) in older individuals without cognitive impairment.

Data were derived from follow-up 2–6 of the prospective Germany Study on Ageing, Cognition and Dementia in Primary Care (AgeCoDe) covering a total six-year observation period. We used linear mixed effects models to estimate the effect of SCD on HRQoL measured by the EQ-5D visual analogue scale (EQ VAS).

Of 1,387 cognitively unimpaired individuals aged 82.2 years (SD = 3.2) on average, 702 (50.6%) reported SCD and 230 (16.6%) with SCD-related concerns. Effect estimates of the linear mixed effects models revealed lower HRQoL in individuals with SCD (unadjusted: –3.7 points on the EQ VAS, 95%CI = –5.3 to –2.1; SE = 0.8; p < 0.001; adjusted: –2.9 points, 95%CI = –3.9 to –1.9; SE = 0.5; p < 0.001) than in individuals without SCD. The effect was most pronounced in SCD with related concerns (unadjusted: –5.4, 95%CI = –7.6 to –3.2; SE = 1.1; p < 0.001; adjusted: –4.3, 95%CI = –5.8 to –2.9, SE = 0.7; p < 0.001).

SCD constitutes a serious issue to older cognitively unimpaired individuals that is depicted in persisting lower levels of HRQoL beyond depressive symptoms and functional impairment. Therefore, SCD should be taken seriously in clinical practice.

Most of the previous studies attempted to disentangle the relationship between disability and depressive symptoms were limited to observation periods of only few years. Moreover, evidence is missing regarding the complex co-occurrence of disability and depressive symptoms in old age in Germany. In order to close the research gap, we aimed at disentangling the complex co-occurrence of disability and depressive symptoms in old age in Germany over a longer time frame.

Based on data from a representative survey of the German general population aged 75 years and older, the course of disability as well as depressive symptoms was observed every 1.5 years over six waves. While disability was quantified by the Lawton and Brody Instrumental Activities of Daily Living scale, the Geriatric Depression Scale was used to measure depressive symptoms. Taking into account the complex co-occurrence of depressive symptoms and disability, a panel vector autoregressive model was used. By taking the first differences, unobserved heterogeneity was taken into account.

In the total sample and in both sexes, we revealed a robust positive association between an initial change in depressive symptoms and subsequent changes in disability. No robust association between an initial change in disability and a subsequent change in depressive symptoms was detected.

Our findings highlight the importance of changes in depressive symptoms for future changes in disability in old age.

The association of subjective memory impairment (SMI) with cognitive performance in healthy elderly subjects is poor because of confounds such as depression. However, SMI is also a predictor for future dementia. Thus, there is a need to identify subtypes of SMI that are particularly related to inferior memory performance and may represent at-risk stages for cognitive decline.

A total of 2389 unimpaired subjects were recruited from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), as part of the German Competence Network on Dementia. Clusters of SMI according to patterns of response to SMI questions were identified. Gender, age, depressive symptoms, apolipoprotein E (apoE) genotype, delayed recall and verbal fluency were included in a Classification and Regression Tree (CART) analysis to identify discriminators between the clusters.

We identified three clusters. Cluster 1 contained subjects without memory complaints. Cluster 2 contained subjects with general memory complaints, but mainly without memory complaints on individual tasks of daily living. Cluster 3 contained subjects with general memory complaints and complaints on individual tasks of daily living. Depressive symptoms, as the first-level discriminator, distinguished between clusters 1 and 2 versus cluster 3. In subjects with only a few depressive symptoms, delayed recall discriminated between cluster 1 versus clusters 2 and 3.

In SMI subjects with only a minor number of depressive symptoms, memory complaints are associated with delayed recall. As delayed recall is a sensitive predictor for future cognitive decline, SMI may be the first manifestation of future dementia in elderly subjects without depression.