During the study, the serum vitamin D levels of 267 adults undergoing outpatient treatment for chronic pain were recorded. The researcher also recorded information about their pain medication dose and duration of use, as well as their physical and general health functioning.
Twenty-six per cent of the study subjects had vitamin D inadequacy, and among those patients, the morphine dose was nearly twice that of the group with adequate vitamin D levels, say the researchers. It was also found that the vitamin D inadequacy group used morphine for an average of 71.1 months, in comparison with patients with adequate nutrient levels who used the pain medication for an average of 43.8 months.
The researchers said that the vitamin D deficient group also reported lower levels of physical functioning, and had a poorer view of their overall health. Dr. W. Michael Hooten, medical director and anaesthesiologist at Mayo Comprehensive Pain Rehabilitation Center, says that it has long been known that inadequate levels of vitamin D can cause pain and muscle weakness.
According to the researcher, it has also been suggested by previous studies that pain-related symptoms of vitamin D inadequacy respond poorly to pain medications. "(However) this is the first time that we have established the prevalence of vitamin D inadequacy among a diverse group of chronic pain patients," Dr. Hooten said.
"The implications are that in chronic pain patients, vitamin D inadequacy is not the principal cause of pain and muscle weakness, however, it could be a contributing but unrecognised factor," the researcher added. Dr. Hooten says that vitamin D inadequacy can be "easily and inexpensively" treated "with essentially no side effects" using a prescription supplement, once or twice a week for four to six weeks.
However, the researcher admits that further study is required to determine whether treating inadequate vitamin D levels can improve the overall general health of patients with chronic pain.