Smoking does not influence disability accumulation in primary progressive multiple sclerosis

Environmental factors related to multiple sclerosis progression

Multiple Sclerosis (MS) is a complex neurological disease which prevalence is increasing worldwide. The impact of environmental factors on MS susceptibility has already been defined and highlighted in many previous reports, particularly vitamin D or ultraviolet B light exposure, Epstein-Barr virus (EBV) infection, obesity, and smoking. There is increasing evidence that environmental and lifestyle factors are not only important in triggering MS but are also implicated in MS progression. Low sun exposure and vitamin D deficiency exhibit a strong relationship with disease progression in both animal and human studies. The gestational period seems also to impact long-term disease progression as January's babies had a higher risk of requiring walking assistance than those born in other months. The implication of EBV in neurodegeneration and MS progression was also suggested even though its specific targets and mechanisms are still unclear. Cigarette smoking is correlated with faster clinical progression. The association of obesity and smoking seems to be associated with a faster progression and an increased rate of brain atrophy. Although the effect of air pollution on MS pathogenesis remains not fully understood, exposure to polluted air can stimulate several mechanisms that might contribute to MS severity. People with MS with active disease have an altered microbiota compared to patients in the remission phase. Cardiovascular comorbidities, epilepsy, and depression are also associated with a more severe disability accrual. Knowledge about MS modifiable risk factors of progression need to be incorporated into everyday clinical practice in order to ameliorate disease outcomes.

Impact of tobacco smoking on disease-specific outcomes in common neurological disorders: A scoping review

Although the association of smoking with the risk of incident neurological disorders is well established, less is known about the impact of smoking and smoking cessation on outcomes of these conditions. The objective of this scoping review was to synthesize what is known about the impact of smoking and smoking cessation on disease-specific outcomes for seven common neurological disorders. We included 67 studies on the association of smoking and smoking cessation on disease-specific outcomes. For multiple sclerosis, smoking was associated with greater clinical and radiological disease progression, relapses, risk for disease-related death, cognitive decline, and mood symptoms, in addition to reduced treatment effectiveness. For stroke and transient ischemic attack, smoking was associated with greater rates of stroke recurrence, post-stroke cardiovascular outcomes, post-stroke mortality, post-stroke cognitive impairment, and functional impairment. In patients with cognitive impairment and dementia, smoking was associated with faster cognitive decline, and smoking was also associated with greater cognitive decline in Parkinson's disease, but not motor symptom worsening. Patients with amyotrophic lateral sclerosis who smoked faced increased mortality. Last, in patients with cluster headache, smoking was associated with more frequent and longer cluster attack periods. Conversely, for multiple sclerosis and stroke, smoking cessation was associated with improved disease-specific outcomes. In summary, whereas smoking is detrimentally associated with disease-specific outcomes in common neurological conditions, there is growing evidence that smoking cessation may improve outcomes. Effective smoking cessation interventions should be leveraged in the management of common neurological disorders to improve patient outcomes.

Role of environmental factors in multiple sclerosis

INTRODUCTION

Environmental factors play a significant role in the pathogenesis and progression of multiple sclerosis (MS), either acting alone or by interacting with other environmental or genetic factors. This cumulative exposure to external risk factors is highly complex and highly variable between individuals.

AREAS COVERED

We narratively review the current evidence on the role of environment-specific risk factors in MS onset and progression, as well as the effect of gene-environment interactions and the timing of exposure We have reviewed the latest literature, by Ovid Medline, retrieving the most recently published systematic reviews and/or meta-analyses and more recent studies not previously included in meta-analyses or systematic reviews.

EXPERT OPINION

There is some good evidence supporting the impact of some environmental risk factors in increasing the risk of developing MS. Tobacco smoking, low vitamin D levels and/or low sun exposure, Epstein Barr Virus (EBV) seropositivity and a history of infectious mononucleosis may increase the risk of developing MS. Additionally, there is some evidence that gene-smoking, gene-EBV, and smoking-EBV interactions additively affect the risk of MS onset. However, the evidence for a role of other environmental factors in MS progression is limited. Finally, there is some evidence that tobacco smoking, insufficient vitamin D levels and/or sun exposure have impacts on MS phenotypes and various markers of disease activity including relapse, disability progression and MRI findings. Clearly the effect of environmental factors on MS disease course is an area that requires significantly more research.

Smoking, obesity, and disability worsening in PPMS: an analysis of the INFORMS original trial dataset

BACKGROUND

Smoking and obesity are recognized modifiable risk factors associated with a higher MS incidence, but their impact on physical and cognitive disability worsening is less clear.

OBJECTIVE

To investigate the impact of smoking and obesity on disability worsening in primary progressive MS (PPMS).

METHODS

We used data from INFORMS (clinicaltrials.gov identifier: NCT00731692), a large randomized-controlled trial in PPMS to compare significant worsening on the EDSS, T25FW, NHPT, and PASAT between smokers and non-smokers, and between BMI groups, at 12, 24, and 33 months of follow-up. We investigated the association of smoking and BMI at screening and the risk of disability worsening with logistic regression models.

RESULTS

Smokers had significantly higher EDSS scores throughout the trial. EDSS was not significantly different between BMI categories. No other outcome measure was significantly different between smokers and non-smokers and between BMI categories throughout the trial. Neither smoking status nor BMI were associated with significant worsening on any outcome measure at any time point during follow-up.

CONCLUSION

Despite the known effects on MS incidence, smoking and BMI were not associated with the risk of physical and cognitive disability worsening over 3 years in this well-characterized PPMS trial cohort.

Socioeconomic status and disability progression in multiple sclerosis: A multinational study

OBJECTIVE

To examine the association between socioeconomic status (SES) and disability outcomes and progression in multiple sclerosis (MS).

METHODS

Health administrative and MS clinical data were linked for 2 cohorts of patients with MS in British Columbia (Canada) and South East Wales (UK). SES was measured at MS symptom onset (±3 years) based on neighborhood-level average income. The association between SES at MS onset and sustained and confirmed Expanded Disability Status Scale (EDSS) 6.0 and 4.0 and onset of secondary progression of MS (SPMS) were assessed using Cox proportional hazards models. EDSS scores were also examined via linear regression, using generalized estimating equations (GEE) with an exchangeable working correlation. Models were adjusted for onset age, sex, initial disease course, and disease-modifying drug exposure. Random effect models (meta-analysis) were used to combine results from the 2 cohorts.

RESULTS

A total of 3,113 patients with MS were included (2,069 from Canada; 1,044 from Wales). A higher SES was associated with a lower hazard of reaching EDSS 6.0 (adjusted hazard ratio [aHR] 0.90, 95% confidence interval [CI] 0.89-0.91), EDSS 4.0 (aHR 0.93, 0.88-0.98), and SPMS (aHR 0.94, 0.88-0.99). The direction of findings was similar when all EDSS scores were included (GEE: β = -0.13, -0.18 to -0.08).

CONCLUSIONS

Lower neighborhood-level SES was associated with a higher risk of disability progression. Reasons for this association are likely to be complex but could include factors amenable to modification, such as lifestyle or comorbidity. Our findings are relevant for planning and development of MS services.