Investigating the causal effect of smoking on hay fever and asthma: a Mendelian randomization meta-analysis in the CARTA consortium

Tea Skaaby*, Amy E. Taylor, Rikke K. Jacobsen, Lavinia Paternoster, Betina H. Thuesen, Tarunveer S. Ahluwalia, Sofus C. Larsen, Ang Zhou, Andrew Wong, Maiken E. Gabrielsen, Johan H. Bjørngaard, Claudia Flexeder, Satu Männistö, Rebecca Hardy, Diana J L Kuh, Sarah J. Barry, Line Tang Møllehave, Charlotte Cerqueira, Nele Friedrich, Tobias N. BontenRaymond Noordam, Dennis O. Mook-Kanamori, Christian Taube, Leon E. Jessen, Alex McConnachie, Naveed Sattar, Mark N Upton, Charles McSharry, Klaus Bønnelykke, Hans Bisgaard, Holger Schulz, Konstantin Strauch, Thomas Meitinger, Annette Peters, Harald Grallert, Ellen A. Nohr, Mika J Kivimaki, Meena Kumari, Uwe Völker, Matthias Nauck, Henry Völzke, Chris Power, Elina Hyppönen, Torben Hansen, Torben Jørgensen, Oluf Pedersen, Veikko Salomaa, Niels Grarup, Arnulf Langhammer, Pål R. Romundstad, Frank Skorpen, Jaakko Kaprio, Marcus R. Munafò, Allan Linneberg

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Observational studies on smoking and risk of hay fever and asthma have shown inconsistent results. However, observational studies may be biased by confounding and reverse causation. Mendelian randomization uses genetic variants as markers of exposures to examine causal effects. We examined the causal effect of smoking on hay fever and asthma by using the smoking-associated single nucleotide polymorphism (SNP) rs16969968/rs1051730. Weincluded 231,020 participants from 22 population-based studies. Observational analyses showed that current vs never smokers had lower risk of hay fever (odds ratio (OR)=0·68, 95% confidence interval (CI): 0·61, 0·76; p<0·001) and allergic sensitization (OR =0·74, 95% CI: 0·64, 0·86; P<0·001), but similar asthma risk (OR=1·00, 95% CI: 0·91, 1·09; P=0·967). Mendelian randomization analyses in current smokers showed a slightly lower riskof hay fever (OR=0·958, 95% CI: 0·920, 0·998; P=0·041), a lower risk of allergic sensitization (OR=0·92, 95% CI: 0·84, 1·02; P=0·117), but higher risk of asthma (OR=1·06, 95% CI: 1·01, 1·11; p=0·020) per smoking-increasing allele. Our results suggest that smoking may be causally related to a higher risk of asthma and a slightly lower risk of hay fever. However, the adverse events associated with smoking limit its clinical significance.
Original languageEnglish
Article number2224
Number of pages9
JournalScientific Reports
Issue number1
Publication statusPublished - 22 May 2017

Structured keywords

  • Brain and Behaviour
  • Tobacco and Alcohol


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