The findings, “Relationship between 25‐Hydroxyvitamin D, bone density, and Parkinson’s disease symptoms,” were published in the journal Acta Neurologica Scandinavia.
Vitamin D deficiency and low bone mass are frequently observed in people with Parkinson’s disease (PD). In fact, one particular study found that lack of this vitamin is more common in people with Parkinson’s (55% of patients) than other populations, such as people with Alzheimer’s disease (41% of patients).
But the relationship between vitamin D levels and Parkinson’s has remained controversial. Some studies suggest that taking vitamin D3 — a form of vitamin D used in supplements — can stabilize the disease, while others see no relation with the risk of Parkinson’s.
However, most studies have focused on limited aspects of the disease and did not include important outcomes — notably, non‐motor symptoms.
Vitamin D has a vital role in bone health, since it promotes calcium absorption and bone mineralization, which keeps bones strong and healthy. It also blocks the release of parathyroid hormone (PTH), an hormone that promotes bone tissue reabsorption and bone thinning.
Some studies support that lack of vitamin D results in a greater risk of falls and fractures in Parkinson’s patients, which can increase hospitalization and even fatal disability. Its levels also have been associated with cognition and mood, as well as stomach malfunction, in people with the disease.
While it is possible that deficits in this vitamin impact several symptoms of PD, the connection remains unclear.
To shed light on this relationship, researchers at the Second Affiliated Hospital of Soochow University and Soochow University, in China, set out to determine if vitamin D levels correlated with bone mineral density (BMD) and non‐motor symptoms in Parkinson’s patients.
The team measured blood levels of 25-hydroxyvitamin D, or 25(OH)D — a precursor of the active form of vitamin D and the most accurate indicator of vitamin D levels in the body — and performed extensive clinical evaluations in 182 Parkinson’s patients as well as 185 healthy people (controls).
Participants were recruited from the Second Affiliated Hospital of Soochow University from March 2014 to December 2017.
Bone mineral density — a measure of bone mass and health — was measured at the lumbar spine and the top of the femur (thigh bone) by bone densiometry, which measures bone loss.
The data showed that people with Parkinson’s had significantly lower vitamin D levels in the blood compared with healthy controls — an average of 49.75 versus 43.40 nanomol per liter of 25(OH)D.
In agreement, low levels of vitamin D (below 50 nmol/l) also were more common in Parkinson’s patients (68.68%) than controls (54.05%).
People with lower vitamin D levels were more likely to fall and experience sleep problems, including difficulty in falling asleep (insomnia). They also had significantly more depression and anxiety.
Mean bone densities in both the spine and femur were lower in PD patients, however no correlation was seen between the levels of BMD and vitamin D.
“Together, these results indicate that vitamin D deficiency may play a role in PD pathogenesis [disease manifestations], while vitamin D supplementation may be used to treat the non‐motor symptoms of PD,” the researchers said.
“As various non-motor symptoms place a burden on individuals with Parkinson’s disease and their caregivers, vitamin D might be a potential add-on therapy for improving these neglected symptoms,” study’s senior author Chun Feng Liu, MD, PhD, said in a press release.
However, the researchers stressed that future studies with a larger sample size are necessary to clarify the role of vitamin D in Parkinson’s disease.