An increasing trajectory of depressive symptoms is associated with a greater risk of dementia, data indicate. The findings suggest that depression may be a prodrome of dementia.
The data, from a 10-year study, also indicate that varying courses of depression may have a different impact on the risk of incident dementia.
Previous studies have only assessed the relationship between dementia and depression at a single timepoint, prompting researchers to explore the relationship over the course of time.
Researchers led by Saira Saeed Mirza, MD, of Erasmus Medical Center in Rotterdam, the Netherlands, obtained data on depressive symptoms from 3325 participants (median age: 74 year, 60% women) in the population-based Rotterdam Study from 1993 through 2004. Five trajectories of depressive symptoms were identified: low maintained Center for Epidemiology Depression Scale (CES-D) scores (low; 2441 [73%]); moderately high then remitting scores (decreasing; 369 [11%]); low starting, increasing, then remitting scores (remitting; 170 [5%]); low starting scores that steadily increased (increasing; 255 [8%]); and maintained high scores (high; 90 [3%]).
Over the course of 26 330 person-years, 434 participants developed incident dementia. Only the trajectory with increasing depressive symptoms was associated with a greater risk of dementia compared to the low depressive symptom trajectory (HR 1.42, 95% CI 1.05–1.94; P=0.024). The results remained the same after adjusting for incident stroke (1.58, 1.15–2.16; P=0.0041), Alzheimer’s disease (1.44, 1.03–2.02; P=0.034), and mortality (1.45, 1.06–1.97; P=0.019).
“This finding is consistent with the prodromal hypothesis, which suggests that depressive symptoms in older age possibly represent a prodrome or an early stage of dementia,” the authors wrote. “Indeed, depressive symptoms might appear as a reaction to underlying subclinical cognitive impairment, and lie in a continuum between subclinical cognitive impairment and overt dementia.”