Older age at DBS surgery raises risk of death over subsequent years

Survival after deep brain stimulation also poorer for those diagnosed in 60s, 70s

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by Andrea Lobo |

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Older Parkinson’s patients undergoing deep brain stimulation (DBS), those in their 60s and 70s at the time of the surgical procedure, as well as those diagnosed at older ages are at a higher risk of death over the following years, according to a nationwide study in South Korea.

Other risk factors for poorer long-term survival after DBS included male sex, the use of public health insurance due to low income (called medical aid in South Korea), and the simultaneous presence of dementia or bone fractures.

“Neurologists should consider these risk factors in assessing the prognosis of PD [Parkinson’s disease] patients undergoing DBS,” the researchers wrote.

The study, “Mortality of Deep Brain Stimulation and Risk Factors in Patients With Parkinson’s Disease: A National Cohort Study in Korea,” was published in the Journal of Korean Medical Science.

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Study into 1,079 Parkinson’s patients given deep brain stimulation surgery

DBS is a surgical treatment for Parkinson’s that involves implanting small wires into specific areas of the brain to stimulate those regions with electrical impulses. The wires are connected to a pulse generator, which is powered by a battery.

It is given to more effectively treat Parkinson’s motor symptoms, such as tremors, rigidity, stiffness, slow movements, and walking difficulties.

Previous studies into mortality risk factors for patients undergoing DBS “were performed at a single center or in a subset of regions, with a small sample size, or in a subset of the population but not in a representative population,” the researchers wrote.

With this in mind, scientists in Ulsan and Seoul conducted a large, nationwide study to assess mortality rates and causes after this surgery, as well as potential risk factors for death following DBS.

They retrospectively analyzed data from the National Health Insurance Service-National Health Information Database to identify Parkinson’s patients given DBS from 2005 to 2017.

Their study included 1,079 patients (53.9% women) with a mean age at diagnosis of 54.1 and a mean age at DBS surgery at age 60.3.

Most patients were diagnosed in their 50s (37.9%) or at younger ages (31%), and underwent DBS surgery in their 60s (39%) or in their 50s (31.1%). Among older patients, 5.1% were diagnosed and 17% underwent the surgery in their 70s.

Most patients (84%) were given the procedure once, 14.5% two times, and 1.6% three or more times.

A majority lived in rural areas (59.8%), had a high income (34.8%), and health insurance coverage (86.4%). Another 13.5% were using medical aid.

Comorbidities, or coexisting health conditions, were reported in most patients (71.9%), with the most common being high blood pressure (53%), followed by abnormal levels of fatty molecules in the blood, like cholesterol and triglycerides (52.1%), and depression (51.8%).

After a post-DBS mean follow-up of 10.6 years, almost one-quarter of these people had died (251 or 23.3%) and their mean age at death was 67.2. Survival rates dropped over time, from 96.9% at one year after DBS to 52.5% at 12 years after the surgery.

The most common cause of death was Parkinson’s disease (47.1%) followed by injury, poisoning, and consequences of other external causes (15.9%); circulatory system diseases (12.8%); and tumors (5.2%).

After adjusting for potential influencing factors such as age at diagnosis, health insurance type, and comorbidities, women were at a 33% lower risk of death after DBS relative to men, analyses showed.

“There is no clear explanation of the mechanism for the sex-related differences; however, additional research is needed,” the researchers wrote.

Patients diagnosed with Parkinson’s in their 60s or 70s showed a three times higher risk of death after the surgery than those diagnosed before their 50s.

Coexisting conditions like dementia also raised mortality risk with DBS

Likewise, those given DBS at older ages where at higher mortality risk over time: a twice higher risk for patients in their 60s and three times higher for those in their 70s compared with patients undergoing the surgery before age 50.

Those with medical aid coverage had a 38% higher risk of death than those with health insurance. No significant differences were observed when considering patients directly by income level or the number of comorbidities.

Among specific coexisting conditions, dementia, which affected 12.4% of these patients, was associated with a nearly two times higher risk of death, and fractures, found in 16.2% of patients and including to the femur and vertebrae, were linked to a 60% higher risk.

“The reasons for the increased mortality in dementia are unclear, although malnutrition, swallowing difficulty, and bedridden status, which may be due to dementia, may be involved,” the researchers wrote.

“The burden of comorbidities such as dementia and fracture are important prognostic factors for mortality in PD with DBS, but further study is needed,” they added.

Overall, the study showed that “older age at diagnosis and surgery, being male, the use of medical aid, and the comorbidity of dementia and fractures were associated with a higher risk of mortality after DBS” for people with Parkinson’s, the team concluded.