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BACKGROUND: Sun exposure has consistently been associated with Multiple Sclerosis (MS) onset, but case samples are predominantly relapse-onset MS (ROMS), and risk estimates have rarely been reported separately for ROMS and progressive-onset MS (POMS). We aimed to determine whether sun exposure prior to disease onset was associated with POMS, and whether the effect differed between POMS and ROMS. METHODS: This nationwide case-control study included 153 POMS cases, 204 incident ROMS cases, and 558 community controls with data from two separate datasets: the PPMS Study (2015-2019) and the Ausimmune Study (2003-2006). Information on time spent in the sun before first MS symptom, skin phenotype, sun protection behavior was collected. Satellite data on ambient ultraviolet radiation (UVR) was used to calculate cumulative UVR dose. Unconditional logistic regression was used with adjustment for covariates. RESULTS: There were consistent dose-response associations, with higher levels of UVR exposure associated with a reduced risk of POMS, both for leisure-time and occupational UVR from age 6 to symptom onset. Associations were overall stronger for POMS than ROMS. For example, cumulative leisure-time UVR dose (per 100 kJ/m2 increment) was associated with POMS (aOR 0.93, 95% CI 0.91-0.95) and the association was slightly weaker for ROMS (aOR 0.96, 95% CI 0.94-0.99) for age 6 to symptom onset (test for interaction p<0.001). CONCLUSIONS: Low levels of sun exposure, throughout the whole life span, are associated with increased risk of POMS and ROMS onset. The sun effects are usually stronger for POMS than ROMS.

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It is unknown whether the currently known risk factors of multiple sclerosis reflect the etiology of progressive-onset multiple sclerosis (POMS) as observational studies rarely included analysis by type of onset. We designed a case-control study to examine associations between environmental factors and POMS and compared effect sizes to relapse-onset MS (ROMS), which will offer insights into the etiology of POMS and potentially contribute to prevention and intervention practice. This study utilizes data from the Primary Progressive Multiple Sclerosis (PPMS) Study and the Australian Multi-center Study of Environment and Immune Function (the AusImmune Study). This report outlines the conduct of the PPMS Study, whether the POMS sample is representative, and the planned analysis methods. The study includes 155 POMS, 204 ROMS, and 558 controls. The distributions of the POMS were largely similar to Australian POMS patients in the MSBase Study, with 54.8% female, 85.8% POMS born before 1970, mean age of onset of 41.44 ± 8.38 years old, and 67.1% living between 28.9 and 39.4° S. The POMS were representative of the Australian POMS population. There are some differences between POMS and ROMS/controls (mean age at interview: POMS 55 years vs. controls 40 years; sex: POMS 53% female vs. controls 78% female; location of residence: 14.3% of POMS at a latitude ≤ 28.9°S vs. 32.8% in controls), which will be taken into account in the analysis. We discuss the methodological issues considered in the study design, including prevalence-incidence bias, cohort effects, interview bias and recall bias, and present strategies to account for it. Associations between exposures of interest and POMS/ROMS will be presented in subsequent publications.

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BACKGROUND: A pro-inflammatory diet has been posited to induce chronic inflammation within the central nervous system (CNS), and multiple sclerosis (MS) is an inflammatory disease of the CNS. OBJECTIVE: We examined whether Dietary Inflammatory Index (DII®)) scores are associated with measures of MS progression and inflammatory activity. METHODS: A cohort with a first clinical diagnosis of CNS demyelination was followed annually (10 years, n = 223). At baseline, 5- and 10-year reviews, DII and energy-adjusted DII (E-DIITM) scores were calculated (food frequency questionnaire) and assessed as predictors of relapses, annualised change in disability (Expanded Disability Status Scale) and two magnetic resonance imaging measures; fluid-attenuated inversion recovery (FLAIR) lesion volume and black hole lesion volume. RESULTS: A more pro-inflammatory diet was associated with a higher relapse risk (highest vs. lowest E-DII quartile: hazard ratio = 2.24, 95% confidence interval (CI) = -1.16, 4.33, p = 0.02). When we limited analyses to those assessed on the same manufacturer of scanner and those with a first demyelinating event at study entry (to reduce error and disease heterogeneity), an association between E-DII score and FLAIR lesion volume was evident (ß = 0.38, 95% CI = 0.04, 0.72, p = 0.03). CONCLUSION: There is a longitudinal association between a higher DII and a worsening in relapse rate and periventricular FLAIR lesion volume in people with MS.

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BACKGROUND: In the general population, variation in the serotonin-transporter-linked polymorphic region ( 5-HTTLPR) has been shown to modify the association between stressful events and depression/anxiety. This has not been examined in people with multiple sclerosis (MS). OBJECTIVE: We examined the interaction between significant life events (SLE), 5-HTTLPR and depression/anxiety. METHODS: A population-based longitudinal cohort of 198 people with MS was followed biannually for 2.5 years. Depression and anxiety symptoms were measured at each review using the Hospital Anxiety and Depression Scale (HADS). SLEs were assessed using a questionnaire based on the Social Readjustment Rating Scale. RESULTS: We found an interaction between SLE load in the previous 12 months and functional variation in the 5-HTTLPR allele type in predicting depression, with the association between SLE load and depression being stronger for those with S/S allele type (ß = 0.21 (95% confidence interval (CI): 0.09-0.33) per 10-unit increase) and S/L (ß = 0.14 (95% CI: 0.05-0.24)) compared to L/L allele type (ß = 0.04 (95% CI: -0.05 to 0.24); pinteraction < 0.001). No convincing evidence of an interaction was found with anxiety. CONCLUSION: We found that the association between SLE load and MS depression severity was stronger among those with one or two copies of the short allele of the 5-HTTLPR. The identification of a gene-environment interaction between SLEs and depression in a population where depression is partly disease-driven is novel.

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BACKGROUND: There is substantial evidence that stress increases multiple sclerosis disease activity, but limited evidence on its association with the onset of multiple sclerosis. OBJECTIVE: To examine the association between stressful life events and risk of first demyelinating event (FDE). METHODS: This was a multicentre incident case-control study. Cases ( n = 282 with first diagnosis of central nervous system (CNS) demyelination, including n = 216 with 'classic FDE') were aged 18-59 years. Controls without CNS demyelination ( n = 558) were matched to cases on age, sex and study region. Stressful life events were assessed using a questionnaire based on the Social Readjustment Rating Scale. RESULTS: Those who suffered from a serious illness in the previous 12 months were more likely to have an FDE (odds ratio (OR) = 2.35 (1.36, 4.06), p = 0.002), and when we limited our reference group to those who had no stressful life events, the magnitude of effect became stronger (OR = 5.41 (1.80, 16.28)). The total stress number and stress load were not convincingly associated with the risk of an FDE. CONCLUSION: Cases were more likely to report a serious illness in the previous 12 months, which could suggest that a non-specific illness provides an additional strain to an already predisposed immune system.

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