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UVB light associated with decreased risk of Parkinson’s disease, according to study

Posted on: October 11, 2017   by  Missy Sturges

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Recently, a study published by the journal Environmental Research found that increased UVB exposure was associated with a reduced risk of developing Parkinson’s disease among individuals under the age of 70 years.

Most of us think of Mohamed Ali or Michael J Fox when we hear Parkinson’s disease.  Both celebrities  developed Parkinson’s disease when they were under 50, and both have retired from public appearances. The average life expectancy following diagnosis is between 7 and 14 years.

Parkinson’s disease (PD) is a progressive neurodegenerative disorder caused by damage to specific nerve cells in the brain, leading to a decrease in dopamine levels. Symptoms of PD include tremors, slow movements, loss of balance and muscle rigidity. Thinking and behavioral problems may also occur. Dementia becomes common in the advanced stages of the disease. Depression and anxiety are also common, occurring in more than a third of people with PD.

PD becomes more common as we age, affecting about one percent of the population over the age of 60. Sadly, there is no cure for the disease; however, symptomatic treatment with L-Dopa helps for a while.

Past research has shown a high prevalence of vitamin D deficiency among PD patients. Additionally, low vitamin D status has been linked with increased PD severity. However, whether vitamin D deficiency is a risk factor or consequence of PD remains unknown.

Additionally, no research to date has evaluated the relationship between sun exposure and PD risk. Therefore, in a new study, researchers used UV exposure data (via a solar radiation database) to evaluate the relationship between UVB exposure and Parkinson’s risk among French individuals using data from the French National Health Insurance (SNIRAM) database. The SNIRAM contains information regarding drug reimbursements and demographics for over 97% of the French population.

Individuals were identified as having Parkinson’s disease if they were prescribed anti-Parkinsonian medications between 2009 and 2012. The researchers evaluated the individual’s time-frame of treatment, number of neurologists/general practitioners visits and demographic information. Individuals who were less than 20 years old, women less than 50 years old who were prescribed bromocriptine specifically to prevent lactation (bromocriptine is also used to treat PD) and those who were treated for drug induced PD were excluded from the study.  Sun exposure was separated into quintiles based on UVB intensity per region:

French chart UVB chart

Here is what the researchers found:

  • A total of 69,010 individuals developed PD over the 3-year period, and there was an average of 12 cases of PD per region in France.
  • Vitamin D supplementation was less common in regions with high UVB exposure.
  • The relationship between sun exposure and PD incidence was quadratic, or u-shaped (p < 0.001).
  • Those who lived in northern France experienced an elevated incidence of PD; however, this relationship was did not exist in older adults.
  • The relationship between UVB exposure and PD incidence was impacted by individual’s age (p < 0.001).
  • The incidence of PD was lower among those <70 years of age who lived in the highest UVB quintile compared to those who lived in the middle and lowest quintile.
  • Those between 45-49 years in the bottom quintile for UVB experienced a 1.18-fold increased risk of developing PD; whereas those between 60-64 years in the bottom quintile only experienced a 1.05-fold increased risk of PD.
  • The top quintile for UVB was associated with a 0.92 reduced risk of developing PD; however, those between 85-89 years experienced a moderate increased risk for PD at the top quintile.
UVB quintile

Figure 2: Risk of PD according to top and bottom quintiles, based off age. Age, sex, deprivation index, density of neurologists, smoking, vitamin D supplementation, and proportion of agricultural land adjusted for.

The researchers concluded,

In this nationwide French ecologic study, there was an age-dependent association between UV-B and PD incidence. Compared to [regions] with average UV-B, lower exposure was associated with higher PD incidence in younger subjects but this association weakened as age increased.”

They continued,

“On the contrary, higher UV-B exposure was inversely associated with PD incidence below 70y and positively associated with PD incidence in older subjects.”

The primary limitations of this study included its use of ecological data and UVB as a marker for vitamin D status.  Ecological data leaves the researchers unable to determine the effect of sun exposure on PD risk at an individual level. In addition, sun exposure offers additional health benefits beyond vitamin D production. Therefore, it is unknown whether vitamin D may offer a protective effect against PD.

Due to the fact that vitamin D is considered safe, low cost and offers a variety of health benefits, the Vitamin D Council recommends individuals with PD (or who are at risk for PD) supplement with 5,000 – 10,000 IU vitamin D3 on days they are unable to receive safe, sensible sun exposure when their shadow is shorter than they are tall. It is important to have your vitamin D levels tested to ensure you are reaching optimal levels.

In order to prove whether maintaining healthy vitamin D levels offers a protective or treatment effect for PD, further research is required.

Citation

Sturges, M. & Cannell, JJ. UVB light associated with Parkinson’s disease risk, according to new study. The Vitamin D Council Blog & Newsletter, 2017.

Source

Kravietz, A. et al. Association of UV radiation with Parkinson disease incidence: A nationwide French ecologic study. Environmental Research, 2017.

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