Assessing Relative Neuropsychologic Performance in Patients with Parkinson’s Requires Comparison to Site-Specific Health Controls
In a study published online in the journal Movement Disorders (September 14, 2018), meta-analysis was used to examine the use of neuropsychologic testing to detect early cognitive impairments in people with Parkinson’s Disease (PD).
There are a wide variety of neuropsychologic tests, some of which have multiple versions. The ability of any of these to assess cognitive deficits in people with PD versus people without PD is unknown. In a meta-analysis, data from 30 normed neuropsychological tests across 20 international studies of approximately 2,908 patients with PD were analyzed. In these studies, 17 of the 20 tests had been used to assess 1,247 healthy controls. Using a 2-step approach, investigators examined the standardized scores of people with PD compared with normative data.
Pooled estimates of differences between those with PD and site-specific healthy controls identified cognitive deficits in patients with PD on 14 tests across 5 commonly assessed domains (attention or working memory, executive function, language, memory, and visuospatial abilities). In contrast, healthy control subjects’ performance was statistically above average on 7 of these tests. Of note was that when studies used published norms for cognitive performance of healthy control subjects instead of site-specific testing, there was high between-study variability that could not be fully explained, and which led to inconclusive results.
The authors of the meta-analysis conclude that normed neuropsychologic tests consistently detect cognitive deficits in patients with PD when compared with site-specific healthy control subjects, but not when published norms are used for comparison. Additional research is needed to identify an appropriate neuropsychologic test that is responsive to intervention and sensitive for cognitive decline in multisite international applications.