Costs associated with multiple sclerosis increase as the disease worsens, according to a study of more than 16,000 patients in 16 European countries.

The study, “New insights into the burden and costs of multiple sclerosis in Europe,” was published in the Multiple Sclerosis Journal.

Researchers obtained their information from patient self-reporting. Patients used the Kurtzke’s Expanded Disability Status Scale (EDSS) to assess the severity of their disease. They also reported on their quality of life and their resource use.

Patients were divided into three categories. Those with a score between 0 and 3 on the EDSS scale were deemed to have a mild disease. The disease of those with scores of 4 to 6.5 was considered moderate. And the disease of those with scores of 7 to 9 was classified as severe.

Patients assessed their health-related quality of life with the EuroQol Five Dimensions questionnaire.

The average age of the 16,808 participants was 51 1/2.

The work capacity of MS patients dropped from 82 percent of a healthy person’s to 8 percent as the severity of the disease increased, researchers said.

Patients’ quality of life scores were about the same as those seen in the general population when they had a mild disease. But they plunged to less than zero when their disease became severe.

The mean annual cost of having a mild form of MS was 22,800 euros, or around $26,300, researchers reported. The cost of having a moderate disease was 37,100 euros, or about $42,800. And the cost of a severe disease was 57,500 euros, or $66,340.

Healthcare accounted for 68 percent of total costs with a mild disease, 47 percent with a moderate disease, and 26 percent for a severe disease.

“Costs are dependent on the availability, use and price of services and on disease severity,” the researchers wrote. “Costs were related to disease severity” in all countries “and were dominated by production losses, non-healthcare costs and DMTs,” or disease-modifying therapies.

Those therapies may be a key reason why the highest percentage of healthcare costs occurred in patients with a mild disease, researchers said. Doctors prescribe a lot of DMTs to this group.

Other factors related to the high percentage were that many patients with mild diseases are still able to work — meaning they incur fewer production-loss costs — and this group requires fewer community services.

As MS becomes more severe, patients’ production losses rise, and they use more community services.

“The intensity of healthcare service use varied widely across the countries,” researchers wrote. “This reflects differences in healthcare organization, medical traditions, ease of access and – most importantly – availability of given services.”

Researchers also assessed patients’ levels of fatigue and cognitive difficulties. Ninety-five percent reported fatigue, and 71 percent cognitive difficulties. Fatigue and cognitive difficulties had  significant impacts on quality of life scores, researchers said.