Cigarette smoking may accelerate disability in multiple sclerosis

Oct 15 2007

Persons with multiple sclerosis who smoke risk increasing the amount of brain tissue shrinkage, a consequence of MS, and the subsequent severity of their disease, new research conducted at the Buffalo Neuroimaging Analysis Center (BNAC) at the University at Buffalo has shown.

The results are based on magnetic resonance images (MRIs) of smokers and nonsmokers in 368 MS patients treated in UB's Jacobs Neurological Institute, the university's Department of Neurology in its School of Medicine and Biomedical Sciences.

Results of the research were presented (Oct. 13, 2007) at the 23rd Congress of the European Committee for the Treatment and Research in Multiple Sclerosis in Prague, Czech Republic.

“Cigarette smoke has many properties that are toxic to the central nervous system, and cigarette smoking has been linked to higher susceptibility and risk of progressive multiple sclerosis,” said Robert Zivadinov, M.D., Ph.D., UB professor of neurology, director of the BNAC and first author on the study.

“Interactions between cigarette smoking and genetic and immunologic factors may point to mechanisms in disease pathogenesis. No previous studies have investigated differences in MRI characteristics between MS cigarette smokers and MS nonsmokers,” he said.

The study included patients from the three most common forms of MS: 253 had relapsing-remitting MS -- acute attacks with full or partial recovery; nine had primary-progressive MS -- steady worsening from onset; and 90 had secondary-progressive MS, characterized by occasional attacks and sustained progression. Another 16 participants had experienced their first MS onset.

Patients ranged in age from 35-55 years, and had been living with MS for an average of 13 years. The Expanded Disability Status Scale (EDSS), an average number derived from measures of various functions of the central nervous system based on scales ranging from 0 to 10, was 3.1. The higher the number, the greater the disability.

Within the study cohort, 128 had a history of smoking: 96 were active smokers who had smoked more than 10 cigarettes-per-day in the three months prior to the study start, and 32 were former

smokers who had smoked cumulatively for at least 6 months sometime in the past. The remaining 240 participants had no active smoking exposure.

The average smoking duration was 17.6 years and the average number of cigarettes smoked per day was 17. There were no significant differences between smokers and nonsmokers based on age, disease duration, disease course and total lifetime use of disease-modifying drugs.

Analysis and comparison of the MRIs from smokers and nonsmokers showed that the smokers had significantly higher disability scores and lower brain volume than the nonsmokers. There also was a significant relationship between a higher number of packs-per-day smoked and lower volume of the neocortex, the portion of the cerebral cortex that serves as the center of higher mental functions for humans.

There were no significant differences in any of the clinical findings between active and former smokers.

“Smoking appears to influence the severity of MS and to accelerate brain atrophy and the disruption of the blood-brain barrier in MS patients,” said Zivadinov. “MS patients should be counseled to stop smoking, or at least to cut down so they can preserve as much brain function as possible.”

Additional researchers on the study, all from the BNAC or the JNI, were Milena Stosic, M.D., Nadir Abdelrahman, M.D., Barbara E. Teter, Ph.D., Frederick E. Munschauer, M.D., Sara Hussein, Jackie Durfee, Michael G. Dwyer, Jennifer L. Cox, Ph.D., Nima Hani, Fernando Nussenbaum and Bianca Weinstock-Guttman, M.D.