A new study from Pakistan finds alarming levels of vitamin D deficiency among women with fibromyalgia while British researchers link incidence of pain to the weather.
Vitamin D has become the focus of much study in recent years as researchers have found it to influence health far beyond its well known benefits to calcium metabolism and bone growth and health. Pain is one area where vitamin D appears to be important with lower intakes and blood levels tending to be associated with more ferequent and severe pain.
Fibromyalgia is a relatively common but poorly understood condition characterised by chronic pain, which is widespread but focused at numerous 'tender points' around the body. Current estimates suggest that in the US between 1% and 2% of the population are diagnosed with fibromyalgia with 90% of sufferers being women.
Researchers at Civic Hospital Karachi, Pakistan, conducted a study involving 40 female fibromyalgia patients who had been diagnosed according to the American College of Rheumatology (ACR) criteria. Blood tests were used to rule out the possibility of other conditions causing pain and then each participant had their serum vitamin D levels checked.
Not one of the 40 participants was considered to have adequate vitamin D levels (>30 ng/ml). The researchers found that 32 (80%) of the women were vitamin D deficient (<20 ng/ml) and the remaining 8 (20%) were considered to have vitamin D insufficiency (21-29 ng/ml). The average vitamin D concentration across all participants was 17.41 ng/ml placing it in the deficient range. In those found to be deficient, women aged 46-75 were found to have marginally lower levels of vitamin D than those aged under 45.
Although this study did not seek to correlate vitamin D levels with the experience of pain it is likely, based on what is known about the role of vitamin D in pain regulation, that it could be a significant contributing factor to pain in women with fibromyalgia. Only large trials looking directly at this potential link can confirm this hypothesis however. The Pakistani researchers expressed concern about the prevelance of vitamin D deficiency and insufficiency in their study and called for large scale studies looking at vitamin D levels in both fibromyalgia patients and the general population.
Meanwhile, the Epidemiology of Functional Disorders (EpiFunD) study in North West England sought to determine the relationship between the weather and the incidence of pain in those with functional disorders (a group which includes fibromyalgia). Over a two year period researchers sent out questionnaires to thousands of individuals and asked them to report on pain they were experiencing on they day they completed the questionnaire. Specifically participants were asked to report 'any pain' and chronic widespread pain (CWP) as defined by the ACR. The questionnaire also asked about mood, sleep quality and any exercise undertaken on the day which may have influenced levels of pain.
Using the above information from 2491 completed questionnaires the researchers used sunshine, precipitation, air temperature and pressure data from a local weather station to determine if weather and pain were linked.
Of the 2491 participants, 42% reported experiencing 'any pain' on the day of the questionnaire completion, and 15% reported experiencing CWP. The researchers' analysis revaled that both types of pain were most frequent during winter and least frequent in the summer months, while autumn and spring fell between the two extremes. Additionally, pain was found to be less frequent on days with more hours of sunshine.
The researchers in this study concluded that there was a significant relationship between sunshine and pain but that factors such as exercising more and experiencing better moods on sunny days could explain at least part of this association.
While neither of these studies provides solid evidence linking a lack of sunlight exposure (which activates vitamin D production in the skin) and vitamin D deficiency to fibromyalgia and the severity of pain, the take home message is that anyone with fibromyalgia would be wise to have their vitamin D levels checked and that getting out in the sunshine as much as possible may well reduce the amount of pain experienced.
Bhatty SA Shaikh NA Irfan M Kashif SM Vaswani AS Sumbhai A Gunpat (2010) Vitamin D deficiency in fibromyalgia Journal of the Pakistan Medical Association 60(11):949-51
Macfarlane TV McBeth J Jones GT Nicholl B Macfarlane GJ (2010) Whether the weather influences pain? Results from the EpiFunD study in North West England Rheumatology 49(8):1513-20