Study: Positive associations found between smoking and risk of ALS

Key takeaways:

• Researchers analyzed 32 studies that examined the association between smoking and ALS.
• Data show a strong correlation between current smokers and risk of developing ALS.

Positive associations were found between smoking and risk of developing ALS, with the strongest correlation found among those who actively smoked, according to research from Tobacco Induced Diseases.

“While smoking is a significant risk factor for various diseases and is well established as the primary preventable cause of death, the relationship between smoking and ALS has been studied extensively, with varying and inconclusive findings,” Yun Hak Kim, MD, PhD, assistant professor in the department of biomedical informatics at Pusan National University, South Korea, and colleagues wrote.

Researchers sought to investigate the association between smoking and ALS through systematic review, meta-analysis and dose-response analysis. They examined medical databases including Medline, Embase, Web of Science, Scopus and ScienceDirect to yield 78 records for initial screening that was pared down to 28 valid case-control and four valid cohort studies published between 1981 and 2021, 10 of which took place in the United States.

Subgroup analyses were performed based on sex, study design and current smoking, whereas restricted cubic spline analysis was used to assess the dose-response relationship between smoking (pack-year) and ALS.

According to results, the unadjusted OR for the overall association between smoking and ALS was 1.14 (95% CI, 1.06-1.22) and the adjusted OR was 1.12 (95% CI, 1.03-1.21), revealing a strongly positive association. Subgroup analysis confirmed and revealed a stronger association among current smokers, with an unadjusted OR of 1.28 (95% CI, 1.1-1.49) and an adjusted OR of 1.28 (1.1-1.48).

“While these proposed mechanisms provide a plausible explanation for the association between smoking and ALS, further research is necessary to fully elucidate the underlying molecular pathways and confirm these hypotheses,” Kim and colleagues wrote.