The new study, published in Journal of Parkinson's Disease, examined the relationship between serum vitamin D and neuropsychiatric function in people with Parkinson's disease (PD) - finding that increased levels of the sunshine vitamin are linked to improved mood and may reduce the risk of developing cognitive impairments.
Led by Dr Amie L. Peterson from the Oregon Health and Sciences University in the US, the team conducted a cross-sectional analysis of 286 patients with PD which indicated that higher serum 25-hydroxyvitamin D levels were associated with lower symptom severity, better cognition, and less depression in the entire group, but the relationships were even stronger in those who were not demented.
"About 30% of persons with PD suffer from cognitive impairment and dementia, and dementia is associated with nursing home placement and shortened life expectancy," explained Peterson. "We know mild cognitive impairment may predict the future development of dementia."
"Intervening in the development of dementia has the potential to improve morbidity and mortality in persons with PD."
The analysis is an add-on study to an ongoing longitudinal study of neuropsychiatric function in people with PD in which patients were given a number of tests measuring global cognitive function, verbal memory, semantic verbal fluency, executive function, and depression. On the same day, serum 25-hydroxyvitamin D levels were measured.
For the entire group, significant negative associations were found between vitamin D levels and disease severity, as measured both by the Hoehn and Yahr Scale and the United Parkinson's Disease Rating Scale motor section.
Mean vitamin D3 levels were higher in those who were not demented, although the differences did not reach statistical significance, said the team.
Peterson and her colleagues reported that for the entire group, higher levels of serum vitamin D3 were associated with greater fluency for naming vegetables and animals and immediate and delayed recall on a verbal learning test.
When the group was divided into those who were demented or not, significant findings with vitamin D were found for fluency and verbal learning only for those who were not demented.
"The fact that the relationship between vitamin D concentration and cognitive performance seemed more robust in the non-demented subset suggests that earlier intervention before dementia is present may be more effective," said Peterson.
A significant negative association was also found for vitamin D levels and depression, as measured by the Geriatric Depression Scale, for both the entire group and those who were not demented, the team added.
While the findings do indicate significant associations between vitamin D status and cognition and mood, the authors pointed out that a cross-sectional study of this cannot determine causation - for instance, does low vitamin D affect cognitive performance, or are persons with more advanced PD and worse cognition less ambulatory, get less sun exposure, and subsequently have lower vitamin D?
Source: Journal of Parkinson's Disease
Volume 1;, Issue 4, Pages 547-55, doi: 10.3233/JPD-130206.
"Memory, mood, and vitamin d in persons with Parkinson's disease"
Authors: Peterson AL, Murchison C, et al