Submitted by Clark Pinyan, MD
Edited by Nandita Keole, MD
Smoking and Amyotrophic Lateral Sclerosis: A Mendelian Randomization Study
. Zhang Y, Fang F. Ann. Neurol
Authors examined the potential causal effect of smoking on ALS using Mendelian randomization method. Genome-wide association study data was reviewed for loci associated with smoking (current or ever smoked ). Over 500,000 total participants study data was compared with genomic data from over 12,000 patients with ALS. Based on this method, smokers were found to have a higher risk of ALS compared with non-smokers and provides (further) evidence for a causal relationship.
Genome linkage studies use genetic markers associated with a risk (such as tendency to smoke, cancer, or hypercholesterolemia), compared with incidence of a particular condition, in this case ALS. This can overcome some limitations of traditional epidemiology such as recall or selection bias, by being independent of patient self-reporting or selection. Furthermore, Mendelian randomization can suggest a causative link if certain conditions are met.
In this study, ever smokers were found to have a higher risk of ALS compared to never smokers, which provides further support for more traditional epidemiological studies.
Comments: Epidemiological studies of ALS can be limited by the sometimes rapid progression of the disease, and this provides information on use of new methods of risk analysis. I think it will become increasingly important to understand how to use whole genomic data to determine risk, not only for researchers but soon for clinicians.