Multiple sclerosis (MS) is an autoimmune neuroinflammatory disorder of the central nervous system, characterized by significant disability. Chronic inflammatory demyelinating polyneuropathy (CIDP) is a related autoimmune neuroinflammatory disorder which affects the peripheral nervous system – leading to progressive difficulties with walking and sensation. Both conditions are costly in terms of healthcare costs and burden on patients. However, we still do not fully understand the risk factors underlying the development of these disorders and need to develop better markers of disease activity to direct appropriate treatment.
Vitamin D is important in modulating the immune system. Reduced vitamin D levels are associated with autoimmune conditions such as MS and type I diabetes. Sunlight and the distance from the equator (latitude) are important in determining vitamin D levels as sun exposure is required to produce vitamin D. Accordingly, the prevalence of autoimmune disorders is also associated with latitude. In Australia, MS is seven times more common in Tasmania (higher latitude) than in Queensland (lower latitude). Importantly, in patients with MS, vitamin D levels are also associated with disease activity and disability. However these factors have never been investigated in CIDP.
This project will examine the rates of CIDP at different latitudes in Australia to determine if prevalence is associated with latitude. In order to determine if vitamin D levels are associated with disability in CIDP, we will measure vitamin D levels in CIDP patients and compare with functional ability. We have developed a comprehensive series of tests to examine function in patients with CIDP, including novel tests of nerve function. We will also compare with a group of MS patients to determine the differences in vitamin D levels across the spectrum. The overall aim is to develop a marker of disease activity and to examine the potential for a trial of vitamin D supplementation.