RRMS Onset Taking Place at Older Ages Over Past 50 Years

Large study of patients in Spain shows leap in age at diagnosis, 1970–2019

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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The first symptoms of relapsing-remitting multiple sclerosis (RRMS) have been appearing increasingly later in life, according to a Spanish study covering nearly five decades.

From the 1970s through the 2010s, the average age at disease onset rose by more than 10 years in both men and women, its researchers reported.

The study, “The age at onset of relapsing-remitting multiple sclerosis has increased over the last five decades,” was published in the journal Multiple Sclerosis and Related Disorders.

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Multiple sclerosis (MS) occurs when the immune system launches damaging attacks on myelin, the fatty substance that covers and protects nerve cell fibers. While RRMS, the disease’s most common form, can develop at any age, most patients experience their first MS symptoms between the ages of 20 and 40.

A number of studies have shown an increase in the “the incidence rate of MS” over recent decades, and a few provide “preliminary evidence” that the age of MS onset has also been rising over those years, this study noted.

10-year increase in age at diagnosis, 1970-2019, at Catalonia center

To verify if this onset “trend is real,” a research team in Barcelona drew on data from 1,622 RRMS patients diagnosed between January 1970 and December 2019. The patients were diagnosed and followed at the researchers’ clinic, a reference center for demyelinating diseases in Catalonia, a region in the country’s northeast with Barcelona as its capital.

About two-thirds (67.4%) of these patients were women, and mean the age at symptom onset (first RRMS symptoms) across the entire group was 31.1.

To determine how onset age had changed over those five decades, the team divided the patients into groups according to the decade in which their first symptoms appeared.

Results showed that disease onset was at increasingly older ages with each passing decade: rising from 23.79 years old in 1970–79 to 27.86 years in 1980–89; then it jumped to 30.07 in 1990–99, and to 32.12 years old in 2000–09. The numbers of newly diagnosed patients also rose with the increases in age over time.

For the final decade examined, 2010–19, the average age at disease onset rose to 34.28 years old, an increase of more than 10 years from the 1970s. Similar changes in onset age were observed when looking at men and women separately.

Of these 1,622 patients, 5.9% had early-onset disease, defined as onset before age 18, and 4% had late-onset disease, defined as onset after age 50. Consistent with the previous findings, the proportion of patients with early-onset disease declined over time, while that of patients with late-onset disease kept rising.

Researchers then reran their analyses in a smaller group of 1,460 patients, excluding those with early and late onset to determine if they had affected previous results.

“Again, the ages at disease onset were progressively higher as the decades progressed, and this trend was statistically significant,” the scientists reported. Specifically, ages rose from 28.38 for RRMS patients diagnosed at their center in 1970–79 to 33.37 years old for those with onset in 2010–19. Increases in age at onset in this smaller patient group were less marked, but still significant, they added.

Criteria for diagnosing MS have improved over the years, speeding its identification and aiding management. These “changes in diagnostic criteria may have contributed to the reported increase in the incidence of MS as well as the increase in age at disease onset,” the researchers wrote.

While the study did not delve into possible causes for increasing age at disease onset, the researchers suggested that “remarkable” recent lifestyle changes may be contributing factors. Specifically, they noted a greater preference for outdoor activities, including sunbathing, a decline in cigarette smoking, and evidence that Epstein–Barr virus infection — a known MS risk factor — is occurring at later ages in developed countries.

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