A novel combination therapy involving computerized cognitive remediation (CR) and transcranial direct current stimulation (tDCS) shows promise in slowing cognitive decline among older adults at high risk for dementia, according to a recent study. The research, conducted at the Centre for Addiction and Mental Health, suggests that this dual approach may offer a synergistic effect, particularly for individuals with remitted major depressive disorder (rMDD) and those with a low genetic risk for Alzheimer's disease.
The study involved 375 older adults with an average age of 72, all of whom had either rMDD, mild cognitive impairment (MCI), or both. Participants underwent cognitive assessments at baseline, two months, and then yearly for three to seven years. The CR consisted of computerized memory and thinking exercises administered in a classroom setting, five days a week for eight weeks, followed by booster sessions every six months. Participants were also encouraged to practice at home online between boosters.
Synergistic Effects of tDCS and Cognitive Training
The tDCS, delivered via a portable device, applied a 2 milliAmp current to the frontal region of the brain for 30 minutes at the beginning of each CR class. This was intended to enhance brain plasticity and optimize the ability to learn from the cognitive exercises. Dr. Tarek Rajji explained, "We chose these two therapies because we thought that they have synergistic effects. tDCS on its own was less likely to be effective but when combined with another therapy like CR — which typically has had mild benefit — it would increase its effect by priming the brain and increase its plasticity."
Notable Outcomes in Specific Subgroups
The study found that participants receiving the combination therapy experienced slower cognitive decline compared to those receiving a sham intervention. This effect was more pronounced in individuals with a low genetic risk for Alzheimer’s disease. Furthermore, participants with rMDD, with or without MCI, showed better outcomes than those with MCI alone.
Implications for Alzheimer's and Depression
Dr. Rajji noted the significance of these findings, particularly for those with rMDD, a group consistently shown to be at double the risk of developing dementia. "The fact that we found the effect mainly in those individuals with remitted rMDD irrespective of whether they also had MCI or not is very exciting because this group has been consistently shown to be at double the risk of developing dementia yet none of the current treatments for MDD reduce this risk. Our treatment offers this possibility for these patients," he said.
Expert Commentary
Dr. David Merrill, a geriatric psychiatrist, commented on the study's implications, stating that it highlights the potential benefits of combination therapies in addressing the multifactorial nature of cognitive decline. "Unlike monotherapies that target isolated pathways, combination approaches recognize that cognitive decline often results from an interplay of genetic, lifestyle, vascular, and neuroinflammatory factors. Leveraging a combination strategy could address these varied risk factors more effectively, potentially delaying the onset of more severe cognitive impairment in at-risk populations."
Future Directions
Looking ahead, researchers emphasize the need for larger-scale studies across diverse populations to validate these findings. Further investigation into the interaction between combination therapies and individual genetic profiles, particularly among those with known risk factors like the APOE ε4 allele, is also warranted. The integration of digital health technologies and biomarkers for real-time tracking of cognitive health and therapy efficacy could further optimize personalized interventions.
