ECT does not increase risk of later dementia

By Naveed Saleh, MD, MS, for MDLinx
Published April 17, 2018

Key Takeaways

Electroconvulsive therapy (ECT) in patients with affective disorders was not associated with incidental dementia, and the use of ECT in patients with severe episodes of mood disorders, including the elderly, can be continued, according to results from a recent study published in The Lancet Psychiatry.

Previously, the potential of ECT—considered the most effective treatment for severe episodes of mood disorders—to effect long-term neurological outcomes was a concern. A link between ECT and dementia has been proposed because one of the acute adverse effects of ECT is memory loss—particularly apparent with bilateral lead placement and an increased number of treatments per patient.

“Although most cognitive deficits resolve within weeks after treatment,” wrote investigators led by Merete Osler,MD, clinical professor, Section of Epidemiology, Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospitals, Frederiksberg, Denmark, “any potential long-term adverse cognitive outcomes are less clear and subject to debate.”

According to the authors, previous results from a three small studies examining the association between ECT administration and incidental dementia have yielded conflicting results. Two studies suggested increased risk, and one suggested a decreased risk. Of note, not only were the sample sizes in these studies small, but they also lacked a reference group consisting of depressed patients who did not receive ECT.

Using data from the Danish National Patient Registry that include all citizens of Denmark, Dr. Osler and colleagues identified subjects aged 10 years and older who were seen in the hospital for the first time with an affective disorder between January 1, 2005, and December 31, 2015. They mined the registry for registered ECTs and physician diagnoses of incidental dementia, after further expanding the definition of dementia to include any patient who refilled at least one prescription of acetylcholinesterase inhibitors.

Of 168,015 patients (average age: 47.1 years) included in this study, 3.5% were administered ECT at least once. Most patients who received treatment were middle-aged. Median follow-up time was 4.9 years, for a total 872,874 person-years logged.

Of 5,901 patients administered ECT at least once, 3.6% developed dementia, for an unadjusted incidence of 70.4 per 10,000 person-years. Of 162,114 patients not treated with ECT, 3.1% developed dementia, for an unadjusted incidence of 59.2 per 10,000 person-years.

In age-matched subjects less than 70 years old, ECT did not increase risk of dementia. In patients aged 70 years and older, ECT exposure was associated with a decreased rate of dementia (HR: 0.68, 95% CI: 0.58–0.80; P < 0.0001); however, during propensity-score matching, this effect was lessened (HR: 0.77; 95% CI: 0.59–1.00; P=0.062).

During the course of this study, 17.6% of subjects died. After adjusting for competing mortality risk, the overall risk of dementia in patients receiving ECT as compared to those who did not receive ECT was not significant (HR: 0.98; 95% CI: 0.76–1.26; P=0.24).

This study is the first to demonstrate that ECT is associated with a lower incidence of dementia in patients aged 70 years and older diagnosed with affective disorders. According to the authors, this lower incidence “might be explained by factors related to patient selection and competing mortality. In younger patients, the incidence of dementia was low and the results were less conclusive.”

A main advantage of this study is that the researchers used a nationwide-population based registry in a country (Denmark) where health care is free. This advantage provided the researchers a large, unanalyzed group of patients from which to draw.

One potential limitation of this study is that it’s possible that not all cases of ECT were included. “Incomplete registration of electrode placement hampered the validity of the estimates based on these data,” wrote the authors.

Dr. Osler and colleagues suggested that the results of this study should assuage any concerns by physicians about the potential for ECT to increase later risk of dementia.

“The findings from this study show that notwithstanding other possible adverse long-term cognitive effects, ECT did not increase the risk of dementia, and support the continued use of ECT in patients with severe episodes of mood disorders, including those who are elderly,” they concluded.

Funding for this study was provided by the Danish Council for Independent Research, Danish Medical Research Council, the Velux Foundation, the Jascha Foundation, and the Doctor Sofus Carl Emil Friis and Olga Doris Friis grant.

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