Parkinson's and Dementia

I have had many opportunities to speak with other PD patients through support groups, conferences, advocacy presentations, individual meetings, and just talking with friends.  Without question, the #1 concern of the majority of patients (perhaps less so with young onset PD) is whether they will end up with dementia.  It is not surprising, since most of us feel the effects of bradyphrenia (slowed mental processing) and wonder if it will get worse.  It is definitely something that should be discussed with your movement disorder specialist if there are any concerns about cognition or memory.  He/she will help determine the likely cause of the problems, which can include depression, side effects from other medication, vitamin B12 deficiency or others.

Problems experienced by many PWP's may include word finding, organization, scheduling, planning, multi-tasking, recall of verbal information, spatial disorientation, hallucinations, loss of "train of thought" or others.  Some of these fall into categories called executive function and working memory.  Typical estimates in the past for the percentage of PD patients with dementia are in the 20-40% range, but some more recent estimates are significantly higher.  In a 2010 Cambridge research paper (Lancet Neurol 2010; 9: 1200–13
Published Online September 28, 2010, DOI:10.1016/S1474-4422(10)70212-X, Behavioural and Clinical Neuroscience Institute, University of Cambridge) states:


"As Parkinson's disease dementia has been associated with mortality, longitudinal estimates of its cumulative prevalence, rather than cross-section estimates, are more accurate representations of true dementia frequency within the Parkinson's disease population, and range from 75% to 90%".

Some doctors are reluctant to talk openly about this subject due to legitimate concerns about patient reaction.  However, if it is important to you and your caregiver to know as much as possible about all aspects of your current condition so that you can participate in decision making and make informed choices for your future, you may want to be insistent.  It is important to understand that your doctor may not always be able to answer your questions, even if he/she would like to.  If you have symptoms that concern you and other causes have been ruled out, ask if he/she will administer the Montreal Cognitive Assessment, which can be done onsite in about 10 minutes. This will give your doctor a good idea of your current condition in potential problem areas related to PD, including mild cognitive impairment. The best way to get the most reliable feedback is to take a full neuropsycholgical assessment with a neuropsychologist.  You should be able to get a referral from your doctor if he/she agrees that it is appropriate.

The two types of dementia most frequently associated with Parkinson's are Parkinson's Disease Dementia (PDD) and Lewy Body Dementia (LBD).  There is some debate as to whether these are actually separate illnesses or the same.  The primary distinction separating the two is time of onset.  LBD is diagnosed if symptoms start before, concurrent, or slightly after onset of PD motor symptoms.  PDD is the diagnosis when symptoms occur years after onset of motor symptoms.  


The primary reason that there has been reluctance to discuss this issue, I think, is that, like Alzheimer's, Parkinson's dementia is considered to be a terminal condition.  Dememtia Guide.com states that for PDD and LBD "the duration of either disease is “several years” from onset of symptoms."  In contrast, the Lewy Body Disease Association (which includes both diseases under the LBD "umbrella" states that "the disease has an average duration of 5 to 7 years. It is possible, though, for the time span to be anywhere from 2 to 20 years, depending on several factors, including the person's overall health, age and severity of symptoms."  This disparity in information can't help but create confusion and anxiety for patients, caregivers, and families.

I recommend these articles/websites for further information:

• Cognitive Impairment (PDF)
• Dementia Webinar (PDF)
• About Lewy Body Disease (Northwest Parkinson Foundation)
• About Dementia (Dementia Guide)