ECT for Depression: No Long-term Dementia Risk

Liam Davenport

March 07, 2018

UPDATED March 9, 2018 // NICE, France — Electroconvulsive therapy (ECT) for severe depression does not appear to raise long-term dementia risk, new research suggests.

A large, retrospective registry analysis of more than 1600 patients who underwent ECT shows that the procedure conferred no additional risk for cognitive impairment relative to matched control persons who did not undergo ECT, even after up to 40 years of follow-up.

Although there was some divergence between patients with affective disorders and those with general psychiatric disorders, that may be due to factors not considered in the study, note the investigators, led by Simon Hjerrild, MD, PhD, Department for Affective Disorders, Aarhus University Hospital, Denmark.

They conclude that "the treatment of severe depression with ECT was not associated with an increase in the risk of developing dementia."

The findings were presented here at the European Psychiatric Association (EPA) 2018 Congress.

Public Concern

Hjerrild began his presentation by pointing out that ECT is associated with short-term cognitive adverse effects, but these effects "have a tendency to disappear." Nevertheless, there is "great public concern" over the potential long-term effects of the treatment.

Although it is possible that ECT might be linked to later dementia risk, he noted that depression is itself associated with dementia.

"Since ECT is the most efficient treatment we have, could efficient treatment early on block the development of severe depression by several episodes and thereby reduce the risk of dementia?" Hjerrild asked.

To investigate, the researchers examined 2010 consecutive patients from the Risskov ECT register who underwent the procedure between 1976 and 2000.

Using the unique social ID numbers provided to all Danish citizens, the investigators linked the ECT register to the Danish National Health Registers, which contain information on hospital admissions and somatic diseases. This allowed them to identify different control groups, which were matched on the basis of age, sex, and admission period.

From this, they gathered data on 1626 patients with affective disorders who underwent ECT for the first time, 4449 patients with affective disorders who did not undergo ECT, and 15,423 patients with nonaffective psychiatric disorders. All were matched for hospital, admission period, sex, and age.

The investigators also identified 162,765 individuals from the general population who did not have any form of psychiatric disorder and who were matched for age and sex.

Data on previous hospital admissions, psychiatric admissions, and somatic disorders were then collated, because these factors can affect the choice of ECT over medications. Hjerrild noted that some chronic somatic disorders are linked to dementia.

Follow-up was conducted at 5 years, 10 years, and until death or the study cutoff date of March 31, 2017.

No Increased Risk

Results showed that the risk of developing dementia among patients who underwent ECT was not significantly different from that of the general population (adjusted hazard ratios [HRs], 0.915 at 5 years; 0.908 at 10 years; and 0.824 at full follow-up).

Curiously, for patients with affective disorders who did not undergo ECT, the risks of developing dementia at the 5-year follow-up and the full follow-up were significantly reduced (HRs, 0.321 and 0.677, respectively). Hjerrild said, "This might be due to some sort of residual confounding."

Patients with nonaffective psychiatric disorders were at increased risk of developing dementia at 5- and 10-year follow-ups (HRs, 2.223 and 1.682, respectively).

Overall, the risks of developing dementia in the three psychiatric patient groups converged over time toward the level seen in the general population.

"Our conclusion is that there is no increased risk of dementia after ECT treatment against the background population, and the slightly decreased risk we see in the non-ECT-treated affective disorders is probably due to some sort of residual confounding that we couldn't control for," said Hjerrild.

After the presentation, session chair Nicolas Ramoz, PhD, INSERM U894, Center of Psychiatry and Neuroscience, Paris, France, asked whether the use of ECT evolved in Denmark between 1976 and 2000.

Hjerrild replied that there had not been many changes, with "another study from 2006 in the same data showing that the usage is very constant."

Christopher C. Abbott, MD, Department of Psychiatry, University of New Mexico School of Medicine, Albuquerque, who was not involved in the study, told Medscape Medical News that this research is "very exciting."

Calling the study "unprecedented," he said it demonstrates that ECT is not associated with increased risk of subsequently developing a neurodegenerative disorder, which is "synergistic" with research by Prof Filip Bouckaert and colleagues from the University of Leuven, in Belgium. Their results showed that the efficacy of ECT is unaffected by age-related brain changes associated with amyloid load, white matter hyperintensities, and hippocampal volume.

Further research from these investigators suggest that ECT may play a role in amyloid clearance, added Abbott.

"These two lines of research show that ECT is effective and safe in late-life mood disorders, and this should help destigmatize ECT," he said.

Explosion of Interest

Approached for comment, Philibert Duriez, MD, Clinique des Maladies Mentales et de L'encéphale, Centre Hospitalier Sainte-Anne, Paris, told Medscape Medical News, "It is very interesting to have an important cohort like this one." He noted that there has been an explosion of interest in ECT in recent years.

"I am impressed by the number of patients. In France, we don't have data like that. We don't know how many ECT courses are done in the whole country, and there are a lot of different practices between towns and cities," he added.

"From an ethical point of view, it's quite difficult to accept that although it's now a very old treatment and very well known, we have such different practices."

Duriez explained that some psychiatric hospitals in France have no access to ECT or can use it only for a very patients with refractory conditions. In his own hospital, use of ECT is third highest in the country. "In France, the priority is to have a similar protocol for this mode of therapy in different places," he said.

He pointed out that in the United States, the "same problem" may be found regarding the absence of countrywide data on the use of ECT. "Frequently I read...articles on how they are lacking data in different states. Just one or two states in the USA have data about what they do in which indications," said Duriez.

Because of the marked differences in ECT practice both within and between countries, the current findings may not be widely applicable, and the period used in the study may also limit the generalizability of the findings.

He said that ECT practice did not change substantially between 1976 and 2000. However, since then, there has been an increase in the use of ECT for patients with depression, and the technique has been modified and updated.

In addition, because of changes in anesthetic use since 2000, the results of such a study would be different if the study were to be repeated in a more recent cohort, Duriez concluded.

The study was funded by the Program for Clinical Research Infrastructure, which is supported by the Lundbeck Foundation and the Novo Nordisk Foundation. The researchers and Dr Duriez have disclosed no relevant financial relationships.

European Psychiatric Association (EPA) 2018 Congress. Abstract OR0064, presented March 5, 2018.

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