People who have higher levels of vitamin B12 in their blood when they’re diagnosed with Parkinson’s disease may be less likely to develop dementia, a study suggests.

The study, “Higher vitamin B12 level at Parkinson’s disease diagnosis is associated with lower risk of future dementia,” was published in Parkinsonism & Related Disorders.

Dementia describes a group of symptoms in which memory and cognitive abilities become impaired enough to affect daily life. Dementia can be part of the non-motor symptoms associated with Parkinson’s disease; it is most common among people who are older and/or have had Parkinson’s symptoms for longer.

Vitamin B12 is a cobalt-containing molecule present in some foods. It is necessary for bodily processes, including red blood cell function and DNA synthesis.

Previous research found that, among people with Parkinson’s, those with cognitive impairment, such as dementia, had significantly lower levels of vitamin B12 in their blood. This suggests the possibility that low vitamin B12 levels predispose certain individuals to dementia.

Researchers decided to further investigate this idea by testing whether vitamin B12 levels at diagnosis were associated with dementia risk later on. To do this, they analyzed clinical data for people with Parkinson’s whose data had been collected as part of the Rochester Epidemiology Project.

They found 25 people with Parkinson’s (17 males, eight females) whose data also included a measurement of blood B12 levels within either one year before or three months after their diagnosis.

“This duration range was chosen to limit the impact of levodopa treatment, which has been associated with increased homocysteine levels and lower vitamin B12 levels,” the researchers wrote.

The median age of the group at diagnosis was 74 years. Of the 25 people included, 15 (60%) were later diagnosed with dementia, at a median age of 79.4 years.

On average, individuals who did not develop dementia had significantly higher vitamin B12 levels when they were diagnosed than those who did (648.5 vs. 452 ng/L).

With additional statistical modeling, the researchers found that a cutoff of 587 ng/L could separate those who did or did not develop dementia, with an overall sensitivity (true-positive rate) of 87% and a specificity (true-negative rate) of 70%.

The researchers further calculated that for every 100 ng/L increase in vitamin B12 levels at diagnosis, there was a statistically significant decrease in dementia risk, such that “a vitamin B12 level of 500 ng/L was associated with a 69% reduced risk of dementia compared with 400 ng/L,” they said.

These data suggest that vitamin B12 levels at Parkinson’s diagnosis are predictive of future dementia risk.

“The association between higher serum B12 levels and decreased dementia risk may provide prognostic information for clinicians as they counsel patients on the disease course of PD and raises further questions regarding the potential importance of vitamin B12 in these patients,” the researchers wrote.

It should be stressed that this was a small, retrospective study, so further research is needed to validate these findings. Additionally, the findings do not directly suggest that taking vitamin B12 supplements would lower the dementia risk — though this may be an avenue for future investigations to explore.

“Prospective evaluation of vitamin B12 status in PD is needed, and consideration of interventional B vitamin supplementation trials should be pursued,” the researchers wrote.