To assess real-world effectiveness of switching disease-modifying therapy (DMT) in pediatric multiple sclerosis (MS) and clinically isolated syndrome (CIS) initially treated with platform injectables on disease activity. Of 2615 pediatric-onset demyelinating disease patients at 12 clinics in the United States (US) Network of Pediatric MS Centers, those with MS/CIS on initial therapy with a platform injectable who switched to another class of platform injectable, oral or infusion DMT were analyzed. Relapse rate was modeled with negative binomial regression, adjusted for preidentified confounders. A total of 212 children switched DMT before age 18 (67% female, 95% MS). Ninety-three switched from injectable to injectable, 76 injectable to oral, and 43 injectable to infusion. Switchers to oral or infusion were older at onset (injectable 12.3 years, oral 13.5 years, and infusion 14.2 years) and switch (injectable 14.6 years, oral 16.0 years, and infusion 15.7 years). Switchers to infusion DMT were more likely to have enhancing lesions (injectable 45%, oral 28%, and infusion 67%). Compared to injectable (annualized relapse rate [ARR] = 0.88, 95% confidence interval [CI] = 0.52-1.48), relapse rates were lower for injectable to oral (ARR = 0.34, 95% CI = 0.20-0.57; rate ratio: 0.38, 95% CI = 0.21-0.69) and injectable to infusion (ARR = 0.18, 95% CI = 0.09-0.37; rate ratio: 0.21, 95% CI = 0.10-0.44) (p < 0.001). Adjusted number needed to treat in person-years to prevent 1 relapse with oral over injectable was 1.84 (95% CI = 1.03-8.69) and infusion over injectable 1.43 (95% CI = 1.00-3.88). Switching from platform injectable to oral or infusion compared to other platform injectable DMT led to better disease control in pediatric MS. Long-term safety data are required. ANN NEUROL 2026;99:715-729.

Older chronological age is associated with decreased multiple sclerosis (MS) relapse rates and increased risk of progressive disease. Measurement of biological age may be more precise than birthdate in understanding these aging effects. In addition to normal aging, MS-related accelerated aging may contribute. Measurement of biological age in adults may be confounded by the effects of natural aging and age-related comorbidities. Examining age extremes can be informative, and demonstrating accelerated biological aging in children would support a hypothesis of MS driving premature aging. We sought to compare epigenetic age in participants with pediatric-onset MS (POMS) and age-similar controls. We performed a multicenter case-control analysis of epigenetic age in a prospectively collected set of whole blood DNA samples and clinical data. Quantitative methylation scores were derived for approximately 850,000 cytosine-phosphate-guanine (CpG) sites. Epigenetic age was calculated based on 4 established epigenetic clock algorithms. Epigenetic age and age acceleration residual (AAR) were compared between participants with POMS and age-similar controls using multivariate regression analysis, adjusted for demographic variables. Epigenetic age and AAR were greater in cases (n = 125, mean age 15.7 years [SD = 2.6], 63.2% female) compared with controls (n = 145, mean age 15.3 years [SD = 3.4], 63.5% female) after adjusting for age, sex, body mass index, tobacco exposure, and socioeconomic status. This difference was statistically significant for 2 of the 4 epigenetic clocks used (Horvath β = 0.31 years [CI = -0.32-0.94], p = 0.33; Hannum β = 1.50 years [CI = 0.58-2.42], p = 0.002; GrimAge β = 0.33 years [CI = -0.30-0.96], p = 0.29; PhenoAge β = 1.72 years [CI = 0.09-3.35], p = 0.004). We observed greater point estimates of epigenetic age in participants with POMS compared with healthy controls in all epigenetic clocks tested. This difference was statistically significant for the Hannum and PhenoAge clocks after multivariable modeling. These results are consistent with those of studies in adult MS and suggest that accelerated aging may be present even in the youngest people living with MS.

Biological age may better capture differences in disease course among people with multiple sclerosis (PwMS) of identical chronological age. We investigated biological age acceleration through metabolomic age (mAge) in PwMS and its association with social determinants of health (SDoH) measured by area deprivation index (ADI). mAge was calculated for three cohorts: 323 PwMS and 66 healthy controls (HCs); 101 HCs and 71 DMT-naïve PwMS; and 64 HCs and 67 pediatric-onset MS/clinically isolated syndrome patients, using an aging clock derived from 11,977 healthy adults. mAge acceleration, the difference between mAge and chronological age, was compared between groups using generalized linear and mixed-effects models, and its association with ADI was assessed via linear regression. Cross-sectionally, PwMS had higher age acceleration than HCs: 9.77 years in adult PwMS (95% CI:6.57-12.97, p=5.3e-09), 4.90 years in adult DMT-naïve PwMS (95% CI:0.85-9.01, p=0.02), and 6.98 years (95% CI:1.58-12.39, p=0.01) in pediatric-onset PwMS. Longitudinally, PwMS aged 1.19 mAge years per chronological year (95% CI:0.18, 2.20; p=0.02), faster than HCs. In PwMS, a 10-percentile increase in ADI was associated with a 0.63-year (95% CI:0.10-1.18; p=0.02) increase in age acceleration. We demonstrated accelerated mAge in adult and pediatric-onset PwMS and its association with social disadvantage.

Low sun and ultraviolet radiation (UVR) exposures have been associated with increased risk of developing pediatric-onset multiple sclerosis (MS); however, their effect on disease course has not been well characterized. We primarily investigated whether there was an association between time spent in the sun in early childhood and risk of relapse in pediatric MS. We secondarily investigated the effect of sun exposure during more recent periods on risk of relapse. We conducted a multicenter cohort study of participants with pediatric-onset MS recruited from 18 pediatric MS clinics across the United States between November 1, 2011, and July 1, 2017. Relapses were identified prospectively after study enrollment; relapses preceding study enrollment were entered retrospectively. Time spent in the sun at various periods of life was measured using a detailed environmental questionnaire, and ambient UVR exposure was determined using zip codes. Multivariable Cox regression models were used to assess the association between time spent in the sun and UVR dose at specific periods of life and the risk of relapse. Models were adjusted for demographic, clinical, and sun exposure-related characteristics. In our cohort of 334 children with MS, 206 (62%) experienced at least one relapse from disease onset to the end of the follow-up period. After adjustment, ≥30 minutes of daily sun exposure during the first summer of life was associated with a lower risk of relapse compared with <30 minutes (adjusted hazard ratio [aHR] 0.67, CI 0.48-0.92, p = 0.01). Greater time spent in the sun during the second trimester of pregnancy was also associated with reduced risk of relapse (aHR 0.68, CI 0.48-0.97, p = 0.04). UVR dose and time spent in the sun later in life were not significantly associated with relapse risk. In this large cohort study of children with MS, greater early childhood and prenatal sun exposure time was associated with lower risk of relapse. Further investigation of sun exposure at other periods is needed to better characterize its impact on disease course and guide potential future interventions.

Sex steroid hormones have been demonstrated to affect the immune system in multiple sclerosis (MS), and puberty may trigger MS activity. We aimed to evaluate the association between menarche and disease course in pediatric MS through comparison of relapse rates across premenarche, perimenarche, and postmenarche periods. This is a retrospective analysis of a prospectively followed female cohort with pediatric-onset MS in the US Network of Pediatric MS Centers database. Perimenarche was considered the period from 1 year before to 1 year after the estimated menarche date based on menarche integer age. Relapses were collected prospectively. Negative binomial and repeated-measures Cox regression models were used to assess the association of pubertal development stage with relapse rate, adjusted for race, body mass index, and disease-modifying therapy (DMT). Of 736 participants (all female; mean onset age 14.4 ± 2.8 years; mean menarche age 11.6 ± 1.4 years), onset was in premenarche in 73, perimenarche in 112 (± 1 year of menarche), and postmenarche in 551. The median time of MS onset was 2.8 years after menarche. Most (86%) were exposed to DMT in follow-up. In adjusted negative binomial analysis, the annualized relapse rate during premenarche was 0.43, perimenarche was 0.65, and postmenarche was 0.43 (premenarche rate ratio [RR] 1.00 (95% CI 0.70-1.43) and perimenarche RR 1.52 (95% CI 1.16-1.99), compared with reference of postmenarche, p = 0.0049. In adjusted repeated-events Cox regression analysis, there was increased hazard to relapse in perimenarche and postmenarche compared with premenarche (perimenarche hazard ratio [HR] 1.78 [95% CI 1.17-2.70] and postmenarche HR 1.67 [95% CI 1.12-2.50], compared with reference of premenarche, p = 0.025). In this analysis, use of oral and infusion DMTs significantly lowered the relapse hazard compared with periods of no DMT use (injectable HR 0.98 [95% CI 0.83-1.15], oral HR 0.48 [95% CI 0.37-0.61], and infusion HR 0.24 [95% CI 0.18-0.31], compared with no DMT, p < 0.001). Onset of puberty may be a time of increase in disease activity and may require consideration of a change in therapeutic approach. Menarche age was used as a surrogate for puberty, and future studies measuring sex steroid hormones may be informative.