A new analysis says that smoking, already suspected of being a risk factor for amyotrophic lateral sclerosis (ALS), definitely is one. (See the 2004 story, Smoking Is Likely ALS Risk Factor, in MDA/ALS Newsmagazine.)
Carmel Armon, professor of neurology at Tufts University School of Medicine in Boston and chief of neurology at Baystate Medical Center in Springfield, Mass., analyzed the medical literature published on smoking and ALS between 2003 and April 2009.
He initially identified 28 studies, only two of which were considered reliable enough to be included in the final results, which were announced Nov. 17, 2009, in the journal Neurology.
About the new findings
The first paper Armon references was published in 2007 in Neurology. It reports on the occupation, education and smoking habits of 364 people with ALS and 392 without the disease in the Netherlands. Smoking was the only factor the researchers studied that, by itself, increased the chance of developing ALS. It raised the risk of the disease 1.6 times over average.
The second study, published in Annals of Neurology in 2009, studied people who were part of the European Prospective Investigation into Cancer and Nutrition (EPIC) database. Out of 517,890 initially healthy subjects, 118 ultimately died of ALS.
Those who reported they were currently smoking at the time they entered the study had almost twice the risk of dying from ALS (1.89 times greater than average) compared to those who never smoked.
Those who classified themselves as "former smokers" at the time of study enrollment had 1.48 times the risk of dying from ALS compared with those who had never smoked.
In addition, the number of years the subjects smoked increased their risk of ALS. Those who smoked more than 33 years had more than a two-fold increased risk of getting ALS compared with those who never smoked.
The number of years passed since quitting smoking was associated with a decreased risk of ALS compared with continued smoking.
Meaning for families with ALS
Compelling data linking smoking to heart disease, respiratory illnesses and cancer already exist, so there are plenty of reasons not to smoke. This newly confirmed association of smoking with ALS is yet another reason to avoid the practice. For those who have relatives with ALS, it's conceivable that avoiding or stopping smoking could significantly tip the balance toward not developing the disease.