Dementia Risk Greater When Depression Symptoms Increase Over Time
Whether depression is a risk factor for dementia or a symptom of an underlying neurodegenerative process is a complex question.
Older adults with high depressive symptoms that increased over time had nearly twice the risk of dementia than those with minimal depressive symptoms, according to new research published in JAMA Psychiatry. Adults with moderate depressive symptoms that increased over time, however, had no elevated risk for dementia.
“Our results suggest that tracking older persons' depressive symptoms over time in clinical settings may help identify individuals at greatest risk for dementia,” wrote Allison R. Kaup, PhD, of the San Francisco Veterans Affairs Medical Center, and her colleagues. They monitored the depressive symptoms of 2488 older adults, average age 74, from Memphis, Tennessee, and Pittsburgh, Pennsylvania, from 1997 through 2002. Adults who developed dementia during those 5 years were excluded from the study.
The researchers then compared the adults' depressive symptoms over time to their risk of developing dementia a decade after baseline (2007-2008), based on dementia medication prescriptions, hospital records, or cognitive decline of more than 1.5 standard deviations with an assessment tool. The authors' analysis accounted for age, sex, race, education, literacy level, body mass index, smoking, and cardiovascular conditions, including diabetes, hypertension, stroke, or heart attack.
Nearly one-third (32%) of the adults had moderate depressive symptoms that increased over time, and 6% had high symptoms that increased over time. The rest consistently had minimal symptoms. The 14% who developed dementia did so an average 3.9 years after the last assessment of depressive symptoms.
Those with high, increasing symptoms had a 1.9-times greater risk of developing dementia than those with minimal symptoms after confounding adjustment. No similar adjusted risk existed for those with moderate, increasing symptoms. Before accounting for cardiovascular health, smoking, and cognitive health changes during depressive assessments, those with moderate symptoms had a1.3-times greater risk of dementia.
Antidepressant use did not appear to affect the risk findings, although only 6% of the cohort took these medications. The fact that cognitive functioning before dementia onset moderated the association found between moderate, increasing depressive symptoms and dementia risk suggests older adults with those symptoms might be responding emotionally to the early stages of cognitive decline.
“Whether depression is a risk factor for dementia vs a symptom of an underlying neurodegenerative process is a complex question,” the authors wrote. “Although our study cannot fully disentangle these possibilities, our results suggest the nature of the depression-dementia relationship may differ depending on the pattern of depressive symptoms.”
Kaup AR, Byers AL, Falvey C, et al. Trajectories of depressive symptoms in older adults and risk of dementia. JAMA Psychiatry. 2016; Mar 16. doi:10.1001/jamapsychiatry.2016.0004.