The study, “Cognitive function in people with and without freezing of gait in Parkinson’s disease,” was published in npj Parkinson’s Disease.
Freezing is a relatively common gait problem in Parkinson’s patients, evident in an individual being unable to move from a certain position, as if “glued to the spot.” This motor symptom is estimated to affect over half of all patients, and it most common in those with more advanced disease. The cause of frozen gait, however, remains unclear.
Previous research has suggested it might be linked to impairments in cognitive abilities, such as poorer executive function — that which enables us to plan, focus attention, remember instructions, and preform multiple tasks.
But many of these studies were done with small patient groups and didn’t take disease severity into account. Whether frozen gait and cognitive problems are linked remains an open question.
Researchers at Oregon Health & Science University assessed 66 Parkinson’s patients with frozen gait, 81 patients without it, and 80 older adults without Parkinson’s. People in these groups were similar in terms of age (averaging about 68 years) and sex distribution (about twice as many men as women).
Participants underwent a comprehensive battery of cognitive tests, as well as physical evaluations. Gait was assessed subjectively with the New Freezing of Gait Questionnaire (N-FOG; FOG stands for freezing of gait). It was also measured objectively, with a test that involved having participants wear sensors while performing certain movements to generate a FOG ratio score. As expected, individuals with frozen gait had more severe FOG-related scores than those without.
Statistical models were used to assess whether the presence or severity of frozen gait was associated with cognition. These models made adjustments for possible confounding variables, including age, sex, education, and motor symptom severity (as assessed by the MDS-UPDRS III).
Compared to people without Parkinson’s, those with this disease had lower scores in multiple domains related to cognition, including executive function and working memory. But among Parkinson’s patients, the presence or absence of frozen gait was not significantly associated with any cognitive scores.
Furthermore, its severity — both the subjective and objective assessments — was not significantly associated with any cognitive measure.
The researchers noted a weak link between one measure of global cognition (Scales for Outcomes in Parkinson’s disease-cognition) and the FOG ratio score among patients with frozen gait. However, this measure failed to reach statistical significance, so random chance cannot be ruled out as an explanation for this result.
“Overall in this large study, we found no statistical differences in cognitive outcomes between people with PD [Parkinson’s disease] who do and do not freeze when taking disease severity into account,” the researchers concluded. “Our findings may have future implications for rehabilitation of FOG, however, findings will need to be validated in a future cohort.”
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