Excess comorbidity flagged in MS patients

By Eleanor McDermid

Patients with multiple sclerosis (MS) have more comorbidities than would be expected for their age, even at the time of diagnosis, say researchers.

"Our findings highlight that the burden of comorbidity even at diagnosis is important for clinicians to consider", Ruth Marrie (University of Manitoba, Winnipeg, Canada) and study co-authors write in Neurology.

"Clinical trials often exclude individuals with (severe) comorbidities, such that we do not fully understand the efficacy, safety, or tolerability of disease-modifying therapies in these individuals."

The team found that 11 of the 12 comorbidities they studied were significantly more common in 23,382 MS patients (71.9% female) than in 116,638 controls matched for age, gender and area of residence.

The rate ratios for the medical comorbidities in patients versus controls ranged from 1.17 for hypertension and diabetes to 2.87 for fibromyalgia, although the latter was present in just 1.31% versus 0.46%, respectively.

And the researchers report a "striking" increase in the prevalence of psychiatric comorbidities, with rate ratios ranging from 1.32 for schizophrenia to 2.04 for depression, "indicating the need for clinical attention to this issue."

Moreover, these comorbidities were generally diagnosed well before the date of the MS diagnosis, with average delays between comorbidity and MS diagnosis dates ranging from 4.56 years for fibromyalgia to 7.12 years for chronic lung disease.

The excess comorbidity was particularly marked in men, with, for example, the rate ratio of hypertension in patients versus controls being 1.16 in women but 1.48 in men. Men also had notably higher rate ratios than women for diabetes, epilepsy and all psychiatric disorders, whereas women had a higher rate ratio for chronic lung disease.

In a linked editorial, William Grant (Sunlight, Nutrition, and Health Research Center, San Francisco, California, USA) and Trond Riise (University of Bergen, Norway) raise the question of whether shared risk factors underlie the increased comorbidity observed in the MS patients.

"If so, recognizing them could lead to recommendations that would reduce the risk of both MS and the comorbid diseases", they say.

Although cautioning that more research into shared aetiology is needed, they say that "[t]he take-home message to physicians and patients [...]is that many chronic diseases have similar underlying lifestyle risk factors, including low ultraviolet exposure and 25(OH)D concentrations, poor diet leading to obesity, low omega-3 fatty acid intake, and smoking."

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