Changes in 'Parkinson's walk' predict dementia
"Subtle changes in the walking pattern of Parkinson's patients could predict their rate of cognitive decline," The Times reports after new research compared the gait of people with Parkinson's disease with those of healthy volunteers.
Parkinson's disease is a condition with three classic features: a tremor, stiff rigid muscles and slow movements, notably a slow, shuffling walk. It also has other symptoms, including Parkinson's dementia, though it can be difficult to predict who will go on to develop dementia.
Researchers wanted to see if comparing the differences in gait (walking pattern) and cognition (thinking) between 121 people newly diagnosed with Parkinson's disease and 184 healthy adults would provide any clues.
As may be expected, the study found measures of both gait and cognition were poorer in people with Parkinson's compared with healthy adults.
They then compared people with Parkinson's who mainly had gait problems with those who mainly had tremor problems.
Though there was no difference in cognitive abilities between the two groups, in those who mainly had gait problems there was a link between this and their cognitive function. That is, if a person had more problems with gait, they tended to have more cognitive problems.
This study will help doctors further understand how gait may be associated with cognition in people with Parkinson's. It suggests that progression in gait problems may be associated with cognitive decline.
While there is currently no cure for dementia, knowing that someone is at a higher risk could help explain often upsetting changes in mood and behaviour, and enable early access to treatment.
Where did the story come from?
The study was carried out by researchers from Newcastle University and was funded by the National Institute for Health Research.
It was published in the peer-reviewed open-access journal, Frontiers in Aging Neuroscience, so the article is free to access online.
The Times' reporting is accurate. But the Daily Mail's coverage is misleading and confusing, as its headline asks, "Could your walk signal dementia?"
This study is specific to Parkinson's disease and people with this condition who go on to develop dementia. It is not relevant to the population at large or to other types of dementia, such as Alzheimer's.
What kind of research was this?
This was a case-control study examining the differences in gait (walking pattern) and cognition (mental abilities) between people newly diagnosed with Parkinson's disease (the cases) and a comparison group of healthy older adults (the controls).
Parkinson's disease is a neurological condition with an unknown cause, where not enough of the chemical dopamine is produced in the brain. This causes characteristic symptoms of:
- a resting tremor – shaking when the person is relaxed
- rigidity – stiff and inflexible muscles
- slow movements – someone with Parkinson's classically walks with slow shuffling steps, and they are generally slower in all movements
As well as these classic symptoms, there are a variety of others, and usually Parkinson's has some mental health effects, including dementia and depression.
While treatments such as Levodopa can help improve symptoms, there is no cure for Parkinson's and the condition usually progresses.
It has been observed that in people who have a predominant tremor (TD), symptoms progress more slowly than those with predominant postural instability and gait disorder (PIGD).
These people who predominantly have problems with walking and balance tend to demonstrate greater decline, not only in terms of movement, but also cognition.
This study aimed to quantitatively measure the differences in movement and cognition between cases and controls. The researchers expected to see a specific association between movement and cognition in people with the different predominant type of Parkinson's.
What did the research involve?
The researchers included 121 people (average age 67) who had been diagnosed with Parkinson's disease in the past four months. They were matched by age and sex to 184 healthy controls, who were able to walk independently and had no specific cognitive or mental health problem.
The Movement Disorder Society (MDS)-revised Unified Parkinson's Disease Rating Scale, which is a well-validated scale, was used to measure disease severity. It was also used to determine which features were predominant – TD (53 people) or PIGD (55 people).
Gait was measured by asking people to walk at their comfortable walking pace for two minutes around a 25m oval walkway. Researchers observed five variables: pace, rhythm, variability in step, asymmetry and posture.
Separately, a range of validated assessment scales were used to measure six domains of cognitive function: global cognition, attention, visual memory, executive function, visuospatial function and working memory.
A range of other tests were performed, including a timed chair stand to assess slow movements and muscle strength. This involved participants being asked to stand up from a seated position with their arms folded across their chest and sit down five times, as quickly as possible.
Balance was measured using the activities balance self-confidence scale, and physical fatigue and depression were also measured.
What were the basic results?
All gait variables were significantly different between healthy controls and people with Parkinson's.
People with Parkinson's walked more slowly, walked less symmetrically, made shorter steps, and overall had a more variable gait.
The only measures that were not different were step velocity variability, swing time and step width. As expected, gait measures were poorer for those with Parkinson's characterised as PIGD compared with TD.
When looking at cognition, cognitive outcomes were significantly poorer for people with Parkinson's compared with controls, with the exception of a measure of attention (choice reaction time).
Cognition was no different between the TD and PIGD types of Parkinson's, with the exception of one measure of executive function (semantic fluency), which was poorer in people with PIGD.
The researchers found some association between gait and cognition in both people with Parkinson's and controls. In the group with Parkinson's, four measures of gait (pace, rhythm, variability and postural control) were correlated with measures of cognition, such as poorer measure of gait and poorer cognition.
Two of these measures (pace and postural control) were also associated with cognition in controls. In both people with Parkinson's and the controls, the strongest association was between pace and attention.
Looking at the different types of Parkinson's, associations between measures of gait and cognition were evident in people with PIGD, but not TD.
How did the researchers interpret the results?
The researchers say their observations provide a basis for understanding the complex role of cognition in Parkinson's gait.
Conclusion
Parkinson's is a neurological disease with characteristic features of tremor, rigidity and slow movements, as well as a variety of other classic symptoms, including Parkinson's dementia.
This case-control study demonstrates how measures of both gait (walking) and cognition are, as would be expected, poorer in people newly diagnosed with Parkinson's disease compared with healthy controls.
The study also demonstrates that in Parkinson's disease, people with a predominant postural instability and gait disorder (PIGD) unsurprisingly have poorer measures of gait than people with predominant tremor disorder (TD).
Though there was little difference in cognitive measures between people with PIGD and TD, in those with PIGD there was a correlation between measures of their gait and cognitive function.
This suggests that progressive gait problems may be associated with progressive cognitive decline in people with Parkinson's disease, though the specific biological mechanisms behind this link were not investigated by this study. The researchers now plan to investigate this link further.
The researchers also acknowledge several limitations with their study, including the relatively small sample size – involving only around 50 people with each subtype of Parkinson's. This means these are small numbers on which to base firm conclusions about the differences between the two subtypes.
There are also other measures the study may not have been able to take into account, including the influence of medication (some had started Levodopa, some not) and depression.
Overall, this study helps doctors to further understand how gait may be associated with cognition in people with Parkinson's, and that predominant gait problems may also be an indicator of more cognitive problems.
While there are no current preventative or treatment implications of these findings in terms of Parkinson's, early recognition of people who may be at risk of dementia is likely to be beneficial.
