Individuals with depressive symptoms that increased steadily over a 10-year period had an increased risk of dementia, although this risk varied across different courses of depression, according to data recently published in The Lancet.
Although depressive symptoms have been studied extensively in order to assess their relationship with incident dementia, these symptoms are not assessed at a single time point. Therefore, to examine the association between course of depression and dementia, researchers measured depressive symptoms in a cohort of adults 55 years of age or older over an 11-year period.
Researchers obtained data for depressive symptoms from 3325 participants (median age 74.88 years; 60% women) between 1993 and 2004. All participants were free from dementia at baseline, but had depressive symptoms from at least one examination round in 1993 to 1995, 1997 to 1999, or 2002 to 2004.
Depressive symptoms were validated with the Dutch equivalent of the Center for Epidemiology Depression Scale (CES-D) and Hospital Anxiety and Depression Scale. The researchers used this data to identify 11-year trajectories of depressive symptoms with latent class trajectory modeling. Participants were screened for dementia at each examination round and were followed for 10 years.
The researchers identified 5 trajectories of depressive symptoms characterized by participants’ CES-D scores: 2441 participants with low CES-D scores (low; 73%), 369 participants with moderately high scores that remitted over the course of the study (decreasing; 11%), 170 participants with low starting scores that increased, then remitted (remitting; 5%), 255 participants with low starting scores that consistently increased (increasing; 8%), and 90 patients with maintained high scores (high; 3%).
A total of 434 participants developed incident dementia over 26 330 person-years. The results showed that the trajectory with increasing depressive symptoms was associated with a higher risk of dementia compared with the low depressive symptom trajectory (hazard ratio [HR]: 1.42; 95% confidence interval [CI]: 1.05-1.94]; P=.024).
This association was consistent after censoring for incident stroke (HR: 1.58; 95% CI: 1.15-2.16; P=.0041), after restricting the results to Alzheimer’s disease as an outcome (HR: 1.44; 95% CI: 1.03-2.02; P=.034), and after accounting for mortality as a competing risk (HR: 1.45; 95% CI: 1.06-1.97; P=.019).
The authors of the study noted that although the remitting trajectory had high depressive symptoms over the first few years of follow-up, individuals in this group did not have a higher risk of dementia compared with individuals with no depressive symptoms.
“This finding might suggest that having severe symptoms of depression at one point in time does not have any lasting influence or predict dementia, although we also observed that the estimates for the remitting trajectory suggested a higher risk of dementia during the short term (0 to 3 years),” they wrote.
The authors also suggest that future studies should examine the potential for using depression trajectories, as opposed to single assessments, as a screening method to identify older adults at risk of dementia.
Mirza SS, Wolters FJ, Swanson SA, et al. 10-year trajectories of depressive symptoms and risk of dementia: a population-based study. Lancet. 2016; doi: 10.1016/s2215-0366(16)00097-3.