What effect does MS have on a person’s lifespan? After years of questions, patients finally get some answers.

Neurologists diagnosing their patients with multiple sclerosis (MS) are quick to point out that it’s not a fatal disease. But new research shows that it may steal as much as six years from patients’ lifespans.

In the first large-scale U.S. study of longevity in MS patients, researchers at Boston University collaborated with colleagues from the University of California, San Francisco, the University of Alabama, and Heinrich Heine University in Düsseldorf, Germany. Bayer Pharmaceuticals, maker of the MS drug Betaseron, sponsored the research.

The scientists examined insurance claims from more than 30,000 MS patients and compared them to those of more than 89,000 controls, excluding people with Medicare or Medicaid and those without health insurance.

Find Out How the Affordable Care Act Affects You »

“Subjects were identified on the basis that there was a diagnosis of MS in the system at some point,” explained study author David Kaufman, ScD, Associate Director of the Boston University Slone Epidemiology Center. “In general, we feel that patients with less severe disease were included.”

Mortality was calculated using government death records. While death due to MS is relatively rare, the researchers concluded that the MS group experienced a 6 year decrease in life expectancy on average.

It’s important to note that the data used in the study was collected between 1996 and 2009.

Looking back at the history of disease modifying therapies (DMTs), according to a timeline provided by the National Multiple Sclerosis Society, there were no MS drugs available prior to 1993 when Betaseron was introduced. Avonex and Copaxone only joined the ranks in 1996. After six more years with only three drug choices, patients were introduced to Rebif in 2002.

What effect, if any, has consistent use of a DMT had on the projected lifespan of a person with MS? Kaufman agrees, “This is an important issue for future research.”

Read More: Should MS Drugs Really Cost $62,000 a Year? »

While the data are newsworthy and may strike fear into the hearts of those who have MS, an estimated lifespan isn’t etched in stone.

There are other contributing factors not addressed by the longevity study, including a person’s overall health, the use of complementary therapies, adherence to DMTs, and the impact of a healthy lifestyle, diet, and exercise routine.

Related News: Smoking May Speed Up MS Progression »

There is a small consolation prize for MS patients. In another recent study, researchers at the Karolinska Institutet in Sweden concluded that the risk that relatives of an MS patient will develop the disease is lower than previously thought.

“Slightly over 28,000 individuals diagnosed with MS from 1968 onwards were identified,” the authors explained in a press release. “By using the Swedish Multi-generation registry, both biological and adopted relatives were identified and the researchers could assess the risks for the different groups.”

They found that the sibling of an MS patient had a seven times greater risk of developing the disease compared to the general population, while the risk was five times greater for the child of an MS patient. The study found no increased risk for grandchildren, nieces, and nephews.

Hodgkin’s Lymphoma and MS: Learn About the Genetic Connection »