There is no evidence to support that there is a strong causal relationship between the rs1051730 T allele and migrainous or non-migrainous headaches in ever smokers, according to a recent Mendelian randomization analysis published in the European Journal of Neurology.
The analysis looked at data from 58,316 participants in the Nord-Trøndelag Health study (HUNT), including the HUNT2 and HUNT3 studies, with information about headache status. Participants were aged 20 years or older and lived in the county of Nord-Trøndelag, Norway, at the time of the study. Smoking status was self-reported and participants were classified as either headache sufferers or headache-free controls depending on whether they had or had not suffered from headaches in the last 12 months. The HUNT sample was genotyped for the rs1051730 C>T single-nucleotide polymorphism using 1 of 3 Illumina HumanCoreExome arrays and imputation was performed using Mimimac3.
Of the participants in the HUNT samples, 25,666 were never smokers, 14,799 were former smokers, and 15,278 were current smokers. Among all participants, 39.4% reported headaches, 12.9% reported migraine, and 26.5% reported non-migrainous headache. Each additional T allele was associated with 0.68, 95% CI 0.55-0.80 additional cigarettes smoked daily among current smokers. The Mendelian randomization analysis showed no association between rs1051730 T alleles and headache in ever smokers (odds ratio [OR] 0.99; 95% CI, 0.95-1.02), never smokers (OR 1.00; 95% CI, 0.96-1.04), or current smokers (OR 1.00; 95% CI, 0.96-1.06).
The results of the study found no evidence for a causal effect of smoking intensity on headache or an association between the rs1051730 T alleles and migraine or non-migrainous headache vs no headache.
This study shows that further research into the relationship between smoking and the prevalence of headache is needed before definite conclusions about causal relationships can be drawn.
Johnsen MB, Winsvold BS, Børte S, et al. The causal role of smoking on the risk of headache. A Mendelian randomization analysis in the HUNT Study [published online May 10, 2018]. Eur J Neurol. October 2018. doi:10.1111/ene.13675