Scientists suggest that vitamin D plays an important role in PD development as they link lower levels of the vitamin with a higher frequency of falls and insomnia.
The team also implicate the neurodegenerative condition in a higher risk of depression, anxiety and a lower mean bone mass density (BMD) of the lumbar spine and femoral neck.
“These results indicate that vitamin D deficiency may play a role in PD pathogenesis, while vitamin D supplementation may be used to treat the non‐motor symptoms of PD,” says the team from Soochow University in China.
“However, the pathogenic role of vitamin D deficiency is far from certain. PD risk significantly increases as vitamin D levels decrease and can be affected by vitamin D‐rich food intake, sunlight exposure and skin colours.”
Vitamin D deficiency
Vitamin D deficiency is widespread in PD patients with studies showing this insufficiency occurring in 55% of patients with PD, 41% of Alzheimer's Disease patients, and 36% of a control population.
Epidemiological study results remain inconsistent with some reporting a higher prevalence of vitamin D deficiency in patients with PD than in controls.
Vitamin D also has a vital role in bone metabolism and a lack of vitamin D is correlated with an increased risk of falls and fractures, which can increase hospitalisation.
Studies have also shown that vitamin D levels are associated with cognition and mood in patients with PD as well as gastrointestinal dysfunction, mainly delayed gastric emptying time.
The team began by enrolling 182 patients with PD and 185 healthy controls. Serum 25‐hydroxyvitamin D (25[OH]D) levels were measured as well as BMD of the lumbar spine and femoral neck.
They found that PD patients had significantly lower serum 25(OH)D levels relative to healthy controls.
Furthermore, PD patients with lower vitamin D levels had a significantly higher frequency of falls and insomnia.
They also had significantly higher scores for the Pittsburgh Sleep Quality Index for depression and anxiety.
Finally, patients with PD also had a significantly lower mean BMD of the lumbar spine and femoral neck.
After adjusting for age, sex, and body mass index, vitamin D levels significantly correlated with falls, insomnia, and scores for the PSQI, depression, and anxiety.
‘Reduced muscle mass and strength’
“In this study, patients with PD had significantly lower serum 25(OH)D levels and mean BMD relative to HC. However, serum 25(OH)D levels and BMD in patients with PD did not significantly correlate,” the study says.
“It is interesting that, in our results, the incidence of falls was higher in patients with lower vitamin D levels, while the scores of Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn‐Yahr scale (H&Y) were not significant.
“The most commonly cited theory for the connection between falls and vitamin D levels is related to reduced muscle mass and strength.”
The Soochow University team go on to discuss the high prevalence of mood disorders common with non‐motor symptoms in patients with PD, adding that though the association is clear, the underlying mechanism and causality remains unknown.
Connections between vitamin D and sleep disorders is also controversial said the team as they suggests that sleep latency and duration could be improved by vitamin D supplementation.
“The vitamin D receptor (VDR) and the enzyme associated with synthesis of the active form of the hormone 1α‐hydroxylase have been mapped in the human brain,” the team highlight. “These molecules may be involved in sleep regulation.”
The researchers also acknowledge study limitations having only evaluated 25(OH)D levels.
They commented on the assortment of different sources of vitamin D used, opening up possibilities that different vitamin D forms may be detected.
“Our study had a relatively small sample size and was cross‐sectional,” they add. “We did not test the serum calcium, phosphate, or parathyroid hormone levels.
“Also. pair‐test in the PD and controls should be performed to improve the reliability, and more replications with pair‐test are needed to explain the association between 25(OH)D levels and PD risk,” they suggest for future study.
Source: Acta Neurologica Scandinavica
Published online: doi.org/10.1111/ane.13141
“Relationship between 25‐Hydroxyvitamin D, bone density, and Parkinson’s disease symptoms.”
Authors: Hui‐Jun Zhang et al.