Do Depression, Lack of Vitamin D, Increase MS Risk?

Multiple sclerosis (MS) patients at diagnosis have a higher rate of comorbid conditions -- including depression and diabetes -- than the general population, conditions which may affect both prevention and treatment, according to a new Canadian study.

These results raise the question of “whether there are shared risk factors for MS and these comorbid diseases. If so, recognizing them could lead to recommendations that would reduce the risk of both MS and the comorbid diseases,” said an editorial accompanying the study in the journal, Neurology.

Lifestyle choices that could be among the common risk factors include low ultraviolet exposure and 25(OH)D [vitamin] concentrations, poor diet leading to obesity, low omega-3 fatty acid intake, and smoking, the editorial said.

The study’s findings also are particularly relevant to MS medications and treatment. “As new disease-modifying therapies for MS emerge for which risks of adverse events differ in the presence of comorbidity, it becomes increasingly important to understand the frequency of comorbidity throughout the disease course, particularly at clinically relevant time point such as at diagnosis,” the lead researcher, Ruth Ann Marrie MD, PhD and her co-authors wrote. Marrie is director of the Multiple Sclerosis Clinic and an associate professor in the departments of internal medicine and community health sciences at the University of Manitoba.

As an example, the study noted that in their population samples, they found that diabetes is more than twice as prevalent among 20-44 year old patients with MS than it was among the control group of the same age. “[D]iabetes increases the risk of macular edema associated with fingolimod (Gilenya /Novartis), a recently licensed oral disease-modifying drug for MS. Therefore, careful assessment of the presence of comorbid conditions is needed when considering such therapies even at the time of diagnosis,” the authors said.

Other diseases significantly more common among MS patients at diagnosis than in the general population sample were: anxiety, bipolar disorder, schizophrenia, hypertension, ischemic heart disease, chronic lung disease, epilepsy, fibromyalgia, and inflammatory bowel disease.

The study also looked at sex differences and their effect on the presence of comorbid diseases among the sample of MS patients. It found that men with MS had “disproportionally higher prevalence” of hypertension, diabetes, epilepsy, depression and anxiety. In both sexes combined, the MS population had a higher prevalence of psychiatric co-morbidities than in the general population sample.

The co-authors based their findings on a comparison of 23,382 incident cases of MS from four Canadian provinces to 166,638 controls matched by age, sex, and geography. However, the relatively high age for diagnosis among the cohort raised a question of selection bias and the representativeness of the cohort, according to the editorial written by William B. Grant PhD, director of the Sunlight, Nutrition and Health Research Center in San Francisco, and his co-author.

The study concluded that “Comorbidity is more common than expected in MS, even around the time of diagnosis. The prevalence of psychiatric comorbidity is particularly high and highlights the need for clinical attention to this issue. The observed sex-specific differences in the burden of comorbidity in MS, which differs from those in the matched population, warrant further investigation.”

The editorial and the study appeared in the April issue of Neurology.