These were the key findings of an analysis of data from the Korea National Health and Nutrition Examination Survey between 2008–2014, and published in the Journal of Exercise Rehabilitation.
Rheumatoid arthritis is the most common autoimmune disease found in about 1% of adults worldwide.
“It is caused by neutrophils, macrophages, T cells, B cells and dendritic cells infiltrating the synovium of joints and causing inflammation. It causes damage to bone and disability,” wrote the researchers from Dongseo University and Daedong Hospital.
“Finally, it induces systemic complications such as cardiovascular and cardiopulmonary dysfunction, and reduces life expectancy by about 3–10 years.”
The researchers decided to assess the impact of vitamin D levels because previous studies have suggested appropriate levels reduce the risk of some chronic inflammatory or autoimmune conditions such as various cancers, infectious diseases, type 1 diabetes, multiple sclerosis, and autoimmune rheumatic disease.
“There are reports that low vitamin D intake is associated with the development of rheumatoid arthritis, or low serum vitamin D level is associated with disease activity or physical disability in rheumatoid arthritis,” they added.
On the other hand, there are reports that vitamin D levels in patients with inflammatory joint disease are not related to arthritis activity.
The subjects were women aged 19 years or older who completed a health questionnaire on rheumatoid arthritis and evaluation of vitamin D status.
The odds ratio of rheumatoid arthritis according to the level of vitamin D was determined by complex sampling design logistic regression. The degree of pain and quality of life of patients with rheumatoid arthritis according to their vitamin D levels were determined by the complex sampling design general linear model.
While the research showed that the odds ratio of rheumatoid arthritis in the lowest vitamin D group was statistically significantly lower than in the group with the highest vitamin D before using covariance, “after using the covariates, all of these statistical differences disappeared.”
Not statistically significant
Similarly, there appeared to be little to note with regard to the level of vitamin D and the difference in pain experienced in women with the condition.
“In the whole rheumatoid arthritis female group, the difference in pain level was not statistically significant depending on the level of vitamin D,” stated the researchers.
“In the present study, there was no difference in quality of life according to the level of vitamin D.”
They added the limitations of this study were that despite the data covering many years, the actual number of patients with rheumatoid arthritis is not large enough, and seasonal effects, sun exposure time, use of drugs, such as disease modifying anti-rheumatic drugs or glucocorticoids, were not controlled.
They concluded: "The results of this study showed that there was no difference in the incidence of rheumatoid arthritis according to the level of vitamin D in Korean adult women and that there was no difference in pain and quality of life when rheumatoid arthritis occurred.
"However, It is necessary to clarify the relationship through a large-scale cohort study that reflects the results of recently reported genome studies. Considering the effect of vitamin D supply on bone density and fracture, and the low price, vitamin D administration with effectiveness analysis is also needed.”
Source: Journal of Exercise Rehabilitation
“Vitamin D status and its associations with rheumatoid arthritis in Korean women: the Korean National Health and Nutrition Examination Survey 2008–2014”
Authors:Taeck-Hyun Lee, et al.