Smoking contributes to disease progression in amyotrophic lateral sclerosis (ALS) and decreases patient survival by about two years regardless of age, gender, or other disease modifiers such as respiratory function, chronic obstructive pulmonary disease (COPD) and ALS-associated gene mutations, according to new research.
These findings suggest that neurologists should advise their ALS patients that quitting smoking will likely help them live longer.
The study, “Influence Of Cigarette Smoking On ALS Outcome: A Population-Based Study,” was published in the Journal of Neurology, Neurosurgery & Psychiatry.
Researchers analyzed 650 ALS patients from the Piemonte/Valle d’Aosta Register for ALS from 2007 to 2011. Information on premorbid cigarette smoking habits and COPD at the time of diagnosis was also analyzed.
ALS severity was assessed with the ALS Functional Rating Scale revised (ALSFRS-R), and the decline rate for ALSFRS-R score was determined by the mean monthly number of points lost from symptom onset to the time of diagnosis, calculated in months.
Patients were defined as current smokers (still smoking at the time of symptom onset; 121 patients), former smokers (patients who quit smoking before the onset of ALS; 182 patients), or never smoked (347 patients).
Researchers registered the forced vital capacity (FVC) to assess the severity of COPD and analyzed the DNA of most patients to look for mutations in the C9ORF72 gene, which has been associated to ALS.
The analysis indicated that current smokers had a significantly shorter median survival (1.9 years) compared with former smokers (2.3 years) and never smoked (2.7 years). This difference was present in both genders, independent of age at onset or mutation status. Also, although COPD was a negative factor influencing patients’ prognosis, presence of this disease did not modify the effect of smoking habits on survival.
In addition, smoking status significantly contributed to the mean monthly decline of ALSFRS-R and its gross motor and respiratory sub-scores.
“Our population-based study found that cigarette smoking is a strong negative modifier of ALS prognosis, independent from age, gender and other known modifiers, including respiratory function, COPD and C9ORF72 status,” the authors wrote.
“According to these findings, neurologists should consider [recommending] to their patients with ALS the cessation of smoking as a measure to significantly improve their outcome.”
“This study indicates that environmental factors and personal habits represent risk factors for ALS onset and can also influence its phenotype and prognosis,” they added.