DLB and PDD: How Are They Different?

Today the blog is about the ways that the two types of LBD—dementia with Lewy bodies (DLB) and Parkinson’s disease with dementia (PDD)—are different. We often talk about how they are the same, and truly, those ways are the most important. But there are a few differences too.

1. Diagnostic criteria. Because DLB was defined by dementia specialists and PDD by movement specialists, they have different criteria. The LBDA offers a chart which shows  similarities and differences between the two criteria. They are more similar than different, but do reflect the different mind sets of their originators. For example, with DLB, "dementia" is required for a diagnosis,  but what it means is not really spelled out. With PDD, dementia is broken down into four specific core issues. (Chart)

In most cases, how a person with LBD is diagnosed will not be an issue; treatment is the same. However, with PDD, as the dementia becomes more prominent, the drugs used for PD may make the dementia worse and may need to be adjusted.

2. Mobility. This is the major difference. In the LBDA chart, Parkinsonism is required for a PDD diagnosis (in the form of a PD diagnosis, usually years prior to dementia). In DLB, it is one of three core issues, equal with visual hallucinations and fluctuating cognition. In our experience, a person diagnosed with DLB will usually movement issues eventually, but they are seldom as severe as they are with PDD. For example, Jim's first wife, Annie, had DLB. She developed the typically weakened facial muscles, but she was ambulatory until very late in her journey. In contrast, our friend, Bill, who had PDD, spent his last years in a wheelchair.

3. Alzheimer’s (AD). Another difference between DLB and PDD is how they pair with Alzheimer's. You probably already know that few dementias are “pure.” That is, a person usually has some combination of two or more types of dementia, not just one. For some reason, the person with DLB is much more likely to have AD (80% of the time) than the person with PDD (less than 20% of the time). They are equally likely to have vascular dementia (VaD) and equally likely NOT to have Frontotemporal dementia (FTD). (Reference)

3. Wandering. The likelihood of AD, where wandering is a common symptom, combines with DLB’s better mobility to make wandering much more likely for people like Annie. This must be considered during residential placement. A person with classic LBD may be placed in an assisted living facility because they don’t need the constant containment that a person with AD needs. (But the additional activity, which can increase stress, may still make this a poor choice!)

As mentioned earlier, the similarities between DLB and PDD are greater, both in numbers and in importance. But concerning differences, what have your experiences been? Feel free to comment!

For more information about Lewy body disorders read our books:
A Caregivers’ Guide to Lewy Body Dementia
Managing Cognitive Issues in Parkinson’s &  Lewy Body Dementia