COPENHAGEN — , early results of a new study showed.
Unlike the previous research, the current analysis used polygenic risk scores for depression, which summarize the estimated effect of genetic variants to determine the potential association with MS disease activity, so results are less likely to be explained by reverse causality.
This study increases awareness of the link between depression and MS, said study investigator Kaarina Kowalec, PhD, assistant professor, College of Pharmacy, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada. “We’re starting to understand how depression affects relapses and disability progression in MS,” she said.
The findings were presented at the 2024 ECTRIMS annual meeting.
Common Comorbidity
Depression is a common comorbidity in patients with MS and is associated with increased relapse and disability progression. Depression risk is partly polygenic in nature, involving numerous common genetic variants, said Dr. Kowalec.
The case-control study included 3420 relapsing-onset MS cases of European ancestry from four existing cohorts in three countries.
The Canadian cohort included those enrolled in a prospective longitudinal study of psychiatric comorbidity in chronic immune-mediated inflammatory disease (IMID), including MS; the Swedish cohort was an MS registry (SSReg) that encompasses 64 MS clinics (the cohort was split into two groups); and the US cohort was enrolled in a clinical trial of combined therapy with interferon and glatiramer acetate (CombiRx) in patients with MS.
The median follow-up in these cohorts ranged from 3 to 5 years.
Not surprisingly, most participants were women (from 71% in one of the Swedish cohorts to 83% in the Canadian cohort), and the age at MS onset ranged from 29 years in the Canadian cohort to 35 years in one of the Swedish cohorts.
The median baseline Expanded Disability Status Scale (EDSS) score was higher in the Canadian cohort (3.5) than in the Swedish (1.5) and US (2.0) cohorts, “reflective of the Canadian cohort being slightly more progressed,” said Dr. Kowalec.
Inherited Variants
To measure depression heritability, researchers generated a polygenic risk score in whole-genome imputed genotypes. The score reflects the number of inherited common genetic variants, weighted by effect sizes.
Researchers investigated the association between depression polygenic risk scores (top 20% vs. bottom 80%) with annualized relapse rate and worsening disability in MS measured by the rate of change in EDSS score. In the US cohort, they also explored the association between depression polygenic risk scores and time to relapse and confirmed EDSS worsening.
Covariates included use of disease-modifying therapy, age, sex, and the first five genetic ancestry principal components. The latter was done to capture residual stratification by genetic ancestry, although Dr. Kowalec stressed analyses were done only in those of European ancestry.
Investigators found a higher depression polygenic risk score was associated with relapse risk (incident rate ratio, 1.23; 95% CI, 1.01-1.49).
“Essentially, for every one standard deviation increase in the depression polygenic score, we found a significant increased hazard of 23% for experiencing a relapse over the follow-up period,” said Dr. Kowalec, who is also affiliated with the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
She noted the Canadian cohort did not have many relapses, while the US and Swedish cohorts “had an increased rate.”
Other analyses examined the risk of having a relapse or worsening disability. Every one SD increase in the depression polygenic risk score was significantly associated with a 2.2 greater risk of experiencing relapse (hazard ratio [HR], 2.20; 95% CI, 1.35-3.60) and a 51% increased risk for confirmed EDSS progression (HR, 1.51; 95% CI, 1.03-2.22).