High Risk of Comorbid Depression in MCI Patients

Pam Harrison

November 25, 2016

Almost one-third of patients with mild cognitive impairment (MCI) also have a diagnosis of depression, new research shows.

"Evidence suggests that the presence of depression in MCI increases the likelihood of progression from MCI to dementia, and in the newly published construct of mild behavioral impairment (MBI), depression is an important subdomain in addition to apathy, impulse control, social cognition, and psychotic symptoms," Zahinoor Ismail, MD, University of Calgary, Alberta, told Medscape Medical News.

"Thus, depression and depressive symptoms are a significant risk factor for cognitive, behavioral, and functional outcomes in older adults who have at most mild cognitive impairment, and as the importance of neuropsychiatric symptoms in older adults emerges, good prevalence estimates are required to inform clinicians and researchers, as well as public health policy and decision makers," he added.

The study was published online November 23 in JAMA Psychiatry.

Risk Factor for Dementia Progression

The systematic review and meta-analysis included 57 studies involving 20,892 patients.

Depression was identified through self-reported rating scales, care-giver rating scales, clinician-administered assessments, or semi-structured clinical interviews.

MCI or its equivalent was analyzed as defined by study authors. "The overall pooled prevalence of depression was 32%," they report.

However, prevalence rates varied depending on whether patients included in the study came from the community or a clinical sample.

Among studies where community patients were included, the prevalence of depression in MCI samples was lower at 25%.

However, when patients were taken from the clinic, the prevalence of depression was higher at 40%, and the difference between the groups was significant (P < .001).

"Intuitively, this makes sense," said Dr Ismail.

It is not hard to imagine that patients who are depressed are more likely to go to their doctor with complaints of depression than people who are not depressed, he notes.

"Whether or not there is an interaction or cumulative effect of depression in patients with MCI on rates of presentation for clinical care is speculative at this point and requires further study," Dr Ismail added.

However, evidence does implicate depression as a risk factor for progression to dementia.

"If depression reflects underlying dementia pathology in some people with MCI, it may be a reflection of underlying dementia burden and increase the likelihood of people being in clinical care as opposed to having MCI in the community without clinical support. Again, further studies are required to explore this finding," he said.

Interestingly, neither how depression was diagnosed in the 57 studies nor the criteria used to identify MCI influenced the overall prevalence of depression in MCI.

Dr Ismail said that good studies haven’t been done yet to determine how to manage depression in MCI. "A rigorous prevalence estimate is a first step," he said.

However, it’s still not clear if patients with a dual diagnosis of MCI and depression should be treated with an antidepressant or antidementia agent.

"We do know that, for the most part, the most rigorous and well-designed antidepressant trials for dementia in depression have been failures," said Dr Ismail.

"So depression in dementia is different than depression in the general population, and if depressive symptoms in MCI are manifestations of underlying dementia pathology, then it is unlikely antidepressants would help."

On the other hand, if depression in MCI is a variant of depression as the medical community understands it then antidepressants might work, Dr Ismail noted.

The more likely scenario is that depression in MCI is a mixture of both manifestations and physicians need to learn how to distinguish one from the other to arrive at the right treatment.

"Depression and depressive symptoms are common and very important in older adults with MCI. Irrespective of how depression is diagnosed in this patient group, the presence of depressive symptoms is an important signal that requires attention and follow-up," Dr Ismail concluded.

JAMA Psychiatry. Published online November 23, 2016. Full article

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