Cigarette smoking associated with increased risk of developing ALS

Feb 14, 2011

Cigarette smoking may be associated with an increased risk of developing the muscle-wasting disease amyotrophic lateral sclerosis (ALS), according to a report in the February issue of Archives of Neurology.

" (ALS) is a of motor neurons affecting more than 5,500 newly diagnosed patients every year in the United States," according to background information in the article. "There is no cure for ALS, and the few available treatments have limited efficacy. About 90 percent of ALS cases are sporadic and of unknown, possibly environmental, origin."

To examine the association between cigarette smoking and ALS, Hao Wang, M.D., Ph.D., of the Harvard School of Public Health, Boston, and colleagues analyzed data from five different long-term studies involving a total of more than 1.1 million participants, of whom 832 had ALS. Follow-up ranged from seven to 28 years.

The rates of ALS in the five studies combined increased with age, and were higher in men than women for all age groups. Those who had ever smoked at the beginning of the study had an increased risk of ALS compared with those who had never smoked. Current had a 42 percent increased risk of developing the disease and former smokers had a 44 percent increased risk.

The risk of developing ALS also increased as the number of pack-years smoked (product of the number of packs per day and the number of years that quantity was smoked). Additionally, the average number of cigarettes smoked per day and the duration of smoking were positively associated with ALS when examined independently and not combined into pack-years. The risk of developing ALS increased by 10 percent for each increment of ten cigarettes smoked per day and by 9 percent for each 10 years of smoking; however, these associations did not persist when never-smokers were excluded. Among those who smoked, the risk of ALS increased as the age they started smoking decreased.

"Several possible mechanisms by which cigarette smoking might influence the risk of ALS have been suggested, including direct neuronal damage from nitric oxide or other components of cigarette smoke (such as residues of pesticides used in tobacco cultivation) or from oxidative stress," the authors write. "Chemicals that are present in cigarette smoke generate free radicals and products of lipid peroxydation, and smokers have a higher turnover of the major antioxidant vitamin C. Exposure to formaldehyde, a by-product of the combustion product of tobacco smoking, was reported in 2008 to be associated with an increased risk of ALS."

"Better understanding of the relation between smoking and ALS may further the discovery of other risk factors and help elucidate the nature of the disease," they conclude.

Explore further: Team follows zinc to uncover pathway that fine-tunes brain signaling

More information: Arch Neurol. 2011;68[2]:207-214.

Related Stories

Chemical exposure may increase risk of ALS

Apr 16, 2008

Preliminary results show that a common environmental chemical may increase the risk of developing amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, according to research that will be presented at ...

International ALS gene search begins

May 16, 2006

U.S. scientists are leading the first international gene search for typical ALS -- amyotrophic lateral sclerosis, also known as Lou Gehrig's disease.

Recommended for you

Premature birth alters brain connections

2 hours ago

Premature birth can alter the connectivity between key areas of the brain, according to a new study led by King's College London. The findings should help researchers to better understand why premature birth ...

Helping stroke patients to regain their independence

7 hours ago

Strokes are the second leading cause of death worldwide; they kill more than one million people in Europe each year accounting for 14% of all deaths. About a third of the 8 million stroke survivors in the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.