Patients with Parkinson’s disease who also have postural hypotension — a drop in blood pressure when standing — experience difficulty thinking when upright, but not when lying down.
So while a patient may seem to have normal mental function during an examination — which is often performed seated or lying — activities while standing and walking may prove difficult for them. This is important because postural, or orthostatic, hypotension affects up to half of Parkinson’s patients.
Underestimating the severity of mental function in this patient group can not only affect the evaluation of individual patients, but also influence research on mental acuity in Parkinson’s.
That’s why researchers behind the study “Effects of orthostatic hypotension on cognition in Parkinson disease” in the journal Neurology are encouraging neurologists to vary patients’ positions when they give them mental-acuity tests.
The research team from Beth Israel Deaconess Medical Center and Boston University, both in Massachusetts, used a battery of tests to check the mental acuity of Parkinson’s patients and a healthy control group.
Those tested included 18 Parkinson’s patients with postural hypotension, 19 Parkinson’s patients without blood-pressure issues, and 18 controls with neither Parkinson’s nor postural hypotension.
Tests were first performed while the participants were lying down, then repeated when they were upright at a 60-degree angle. Researchers kept track of the participants’ blood pressure during the testing.
“As we suspected, people with both Parkinson’s disease and orthostatic hypotension showed posture-related impairments when upright relative to supine on nearly all measures of cognition,” Justin Centi, a physician who was lead author of the study, said in a news release.
These patients performed worse on tests of language, math, memory, and attention when standing. That explains why they might have trouble maintaining a conversation while upright or dealing with traffic.
The examining position did not influence the results of mental-acuity tests in patients without blood-pressure drops, and it was the same with the controls.
“The cognitive performance that we see in those patients with Parkinson’s disease who are tested when seated or lying down, in fact, may underestimate their cognitive problems in real life, when they are standing up and going about their business of daily activities,” said Alice Cronin-Golomb, PhD, co-senior author of the study. She is director of Boston University’s Vision and Cognition Laboratory and Center for Clinical Biopsychology.
“Also, the patterns of brain activity that we see on imaging when they are lying down may not be the patterns that the brain produces during normal upright activity,” she said.