A study from Denmark has revealed that individuals with Parkinson’s disease who show mild cognitive changes before undergoing deep brain stimulation (DBS) aren’t at a higher risk for developing dementia later on compared to those who had normal cognitive function. Interestingly, the research indicated that those diagnosed with Parkinson’s for a longer period before the surgery were more likely to face dementia, regardless of their age, gender, or educational background.
The team noted, “Disease duration, but not presurgical MCI [mild cognitive impairment] was associated with development of dementia,” and they emphasized that the impact on cognition was assessed in a follow-up study extending up to 15 years post-DBS.
The study, titled “Mild cognitive impairment is not predictive of dementia up to 15 years after subthalamic deep brain stimulation in Parkinson’s disease,” was published in the Journal of Parkinson’s Disease.
Cognitive Skills Decline Post-DBS
In DBS, tiny electrodes are implanted in specific areas of the brain, connecting to a pulse generator which delivers mild electrical pulses to help manage the characteristic motor symptoms of Parkinson’s. However, many patients also experience cognitive changes, often starting as mild cognitive impairment, which can affect attention, planning, or memory—issues beyond typical aging. When these interfere with everyday activities, they are termed dementia.
The researchers stated, “Cognitive impairment and dementia are common in [the] later stages of Parkinson’s,” yet there’s limited understanding of how DBS affects cognitive function over time. They pointed out that such studies need to account for disease progression alongside the inherent risk of dementia.
To explore the long-term impacts of DBS on cognition, the study tracked 81 patients who had lived with Parkinson’s for roughly 13 years. Notably, half of these individuals already displayed mild cognitive impairment prior to the surgery.
Three months after the DBS procedure, all patients exhibited noticeably reduced verbal fluency. This was measured by how quickly they could name words in a category or starting with a specific letter, or their ability to switch between types of words. While declines in other cognitive areas were noted, the changes weren’t considered significant.
Other Factors Related to Dementia
In total, 29 patients were monitored for a period of up to 15 years, where about two-thirds showed signs of mild cognitive impairment or dementia. Notably, six patients (or 21%) had cognitive changes without a clinical dementia diagnosis.
Among the four patients—who all were women—that had normal cognitive function, they were generally younger (averaging 47.4 years old compared to 57.5) and had also experienced Parkinson’s for a shorter time prior to surgery (8.5 years versus 12 years).
The study found no direct correlation between mild cognitive impairment prior to surgery and subsequent dementia development. Roughly 51% of those with early cognitive issues eventually developed dementia, compared to 55% of those with normal cognitive function before the operation.
Disease duration and … depressive symptoms before surgery were associated with the later development of clinically diagnosed dementia.
Another intriguing finding was that living with Parkinson’s for an extended period prior to surgery increased the risk of developing dementia. For each additional year with the disease before the procedure, the likelihood of developing dementia increased by approximately 20%.
Additionally, around a third of the participants exhibited depressive symptoms before the operation. These symptoms can emerge as a nonmotor symptom of Parkinson’s and may relate to diminished cognitive function. Those with depressive symptoms were more prone to developing dementia later on, as indicated by the findings.
The researchers acknowledged a limitation in their study due to the relatively small sample size and the absence of a control group, which “makes it difficult to draw a conclusion” across all data. They suggested that the findings could generate hypotheses for future research.
