SCD, anxiety symptoms may be independent predictors of MCI/dementia risk

Subjective cognitive decline (SCD) or anxiety symptoms in older individuals are independently associated with an increased risk of mild cognitive impairment (MCI) or dementia, a recent study has shown.

“This study … provided more conclusive evidence on the independent effects of anxiety and SCD on the subsequent development of neurocognitive disorders,” said study author Dr Tau Ming Liew from Singapore General Hospital and the Saw Swee Hock School of Public Health, National University of Singapore.

Study participants were 14,066 individuals aged ≥50 years (median age 71 years, 34.5 percent male, 78.9 percent White) with normal cognition at baseline who were recruited from 39 Alzheimer’s disease centres in the US, as per the National Alzheimer’s Coordinating Center database. SCD and anxiety symptoms were documented at baseline and incident MCI or dementia assessed annually.

At baseline, 9.0 and 27.1 percent of participants reported symptoms of anxiety and SCD, respectively. Median follow-up was 4.5 years. During this time, 10.9 and 5.4 percent of participants developed MCI and dementia, respectively.

SCD and anxiety symptoms were independently associated with an increased risk of MCI or dementia (adjusted* hazard ratio [adjHR], 1.9, 95 percent confidence interval [CI], 1.7–2.1 [SCD] and adjHR, 1.3, 95 percent CI, 1.2–1.5 [anxiety]; p<0.001 for both vs no symptoms). [Alzheimers Res Ther 2020;12:107]

MCI or dementia risk was further elevated among participants who had symptoms of both SCD and anxiety (adjHR, 2.4, 95 percent CI, 1.9–2.9; p<0.001).

In sensitivity analyses, severity of anxiety symptoms affected MCI or dementia risk, with a higher risk noted among participants with severe symptoms (adjHR, 2.3; p=0.004) than those with mild or moderate symptoms (adjHR, 1.3; p=0.004 and adjHR, 1.4; p=0.032, respectively) compared with no symptoms. MCI or dementia risk was higher in participants with consistent SCD symptoms (present at year 1 and 2 of annual visits; adjHR, 2.5) than those with inconsistent symptoms (present at only year 1 or 2; adjHR, 1.6; p<0.001 for both vs no symptoms). However, MCI or dementia risk remained similar regardless of consistency of anxiety symptoms (adjHR, 1.7; p=0.013 [consistent] and adjHR, 1.6; p<0.001 [inconsistent]). 

Participants without anxiety or SCD had a 25 percent risk of developing MCI or dementia by 8.2 years, compared with just 3.1 years among those with both anxiety and SCD.

SCD typically involves a decline in the memory domain of individuals with otherwise normal cognition, said Liew. It is becoming increasingly common in the elderly and is a known predictor of neurocognitive disorders, he said.

Its frequent presence alongside anxiety symptoms has raised the question as to which condition may predict subsequent neurocognitive disorders.

“[T]his study demonstrated that the two likely represent distinct constructs which independently predict the risk of neurocognitive disorders,” he said. “Clinicians should not dismiss one over the other when patients present with both anxiety and SCD.”

“[T]he co-occurrence of both should alert clinicians to the much higher risk of neurocognitive disorders, which may then prompt more intensive interventions to prevent cognitive decline …, enrolment into preventive trials for dementia, and closer monitoring of cognitive function over time to allow timely diagnosis of cognitive impairment,” he continued. However, he acknowledged that the focus on the memory domain for SCD and one-time and single question assessments of anxiety and SCD were potential limitations.

Liew also pointed out the possible “differences in the underlying neurodegenerative processes between SCD and anxiety” with either “two distinct neurobiological pathways that lead to neurocognitive disorders, or a common neuropathology that has affected two distinct anatomical regions in the brain.”