Ryan Ramanujam1, Anna-Karin Hedström2, Ali Manouchehrinia3, Lars Alfredsson4, Tomas Olsson3, Matteo Bottai5, Jan Hillert3. 1. Department of Clinical Neuroscience, Karolinska Institutet at Karolinska University Hospital Solna, Stockholm, Sweden2Department of Mathematics, KTH-Royal Institute of Technology, Stockholm, Sweden. 2. Institute of Environmental Medicine, Unit of Cardiovascular Epidemiology, Karolinska Institutet, Stockholm, Sweden. 3. Department of Clinical Neuroscience, Karolinska Institutet at Karolinska University Hospital Solna, Stockholm, Sweden. 4. Institute of Environmental Medicine, Unit of Cardiovascular Epidemiology, Karolinska Institutet, Stockholm, Sweden4Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden. 5. Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Abstract
IMPORTANCE: Smoking tobacco is a well-established risk factor for multiple sclerosis (MS), a chronic inflammatory disorder of the central nervous system usually characterized by bouts and remissions and typically followed by a secondary progressive (SP) course. However, it is not clear whether smoking after diagnosis is detrimental. OBJECTIVE: To determine whether smoking after MS diagnosis is associated with a change in time to SP disease. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study of patients with prevalent MS who smoked at diagnosis (n = 728) taken from the Genes and Environment in Multiple Sclerosis Study, which consists of patients from the Swedish National MS Registry. The study entrance date was at time of first-year smoking. The study was conducted between November 2008 and December 2011, with patient environmental data collected from November 2009 to March 2011 via questionnaire. Study participants were from all counties in Sweden diagnosed as having MS at the time of the Genes and Environment in Multiple Sclerosis Study and registered in the Swedish National MS Registry. Patients with MS with relapsing-remitting disease course or SP were included. These patients' conditions were diagnosed according to the McDonald criteria and the patients responded to recruitment letters with detailed questionnaires. EXPOSURE: Smoking, considered yearly after diagnosis and combined into a time-invariant covariate before diagnosis. MAIN OUTCOMES AND MEASURES: Time to SPMS, measured using an accelerated failure time model, with smoking as a time-varying covariate. Other covariates included sex, age at diagnosis, snuff use, and smoking before diagnosis. RESULTS: The optimized model illustrated that each additional year of smoking after diagnosis accelerated the time to conversion to SPMS by 4.7% (acceleration factor, 1.047; 95% CI, 1.023-1.072; P < .001). Kaplan-Meier plots demonstrated that those who continued to smoke continuously each year after diagnosis converted to SPMS faster than those who quit smoking, reaching SP disease at 48 and 56 years of age, respectively. CONCLUSIONS AND RELEVANCE: This study provides evidence that continued smoking is associated with an acceleration in time to SPMS and that those who quit fare better. Therefore, we propose that patients with MS should be advised to stop smoking once a diagnosis has been made, not only to lessen risks for comorbidities, but also to avoid aggravating MS-related disability.
IMPORTANCE: Smoking tobacco is a well-established risk factor for multiple sclerosis (MS), a chronic inflammatory disorder of the central nervous system usually characterized by bouts and remissions and typically followed by a secondary progressive (SP) course. However, it is not clear whether smoking after diagnosis is detrimental. OBJECTIVE: To determine whether smoking after MS diagnosis is associated with a change in time to SP disease. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study of patients with prevalent MS who smoked at diagnosis (n = 728) taken from the Genes and Environment in Multiple Sclerosis Study, which consists of patients from the Swedish National MS Registry. The study entrance date was at time of first-year smoking. The study was conducted between November 2008 and December 2011, with patient environmental data collected from November 2009 to March 2011 via questionnaire. Study participants were from all counties in Sweden diagnosed as having MS at the time of the Genes and Environment in Multiple Sclerosis Study and registered in the Swedish National MS Registry. Patients with MS with relapsing-remitting disease course or SP were included. These patients' conditions were diagnosed according to the McDonald criteria and the patients responded to recruitment letters with detailed questionnaires. EXPOSURE: Smoking, considered yearly after diagnosis and combined into a time-invariant covariate before diagnosis. MAIN OUTCOMES AND MEASURES: Time to SPMS, measured using an accelerated failure time model, with smoking as a time-varying covariate. Other covariates included sex, age at diagnosis, snuff use, and smoking before diagnosis. RESULTS: The optimized model illustrated that each additional year of smoking after diagnosis accelerated the time to conversion to SPMS by 4.7% (acceleration factor, 1.047; 95% CI, 1.023-1.072; P < .001). Kaplan-Meier plots demonstrated that those who continued to smoke continuously each year after diagnosis converted to SPMS faster than those who quit smoking, reaching SP disease at 48 and 56 years of age, respectively. CONCLUSIONS AND RELEVANCE: This study provides evidence that continued smoking is associated with an acceleration in time to SPMS and that those who quit fare better. Therefore, we propose that patients with MS should be advised to stop smoking once a diagnosis has been made, not only to lessen risks for comorbidities, but also to avoid aggravating MS-related disability.
Authors: Caila B Vaughn; Dejan Jakimovski; Katelyn S Kavak; Murali Ramanathan; Ralph H B Benedict; Robert Zivadinov; Bianca Weinstock-Guttman Journal: Nat Rev Neurol Date: 2019-06 Impact factor: 42.937