Smoking and infertility: multivariable regression and Mendelian randomization analyses in the Norwegian Mother, Father and Child Cohort Study
Author
Hernáez, Álvaro
Wootton, Robyn E.
Fraser, Abigail
Magnus, Per
Lawlor, Deborah A.
Other authors
Universitat Ramon Llull. Facultat de Ciències de la Salut Blanquerna
Publication date
2022-07Abstract
Objective
To investigate the association between smoking and infertility.
Design
Prospective study.
Setting
Nationwide cohort.
Patients
28,606 women and 27,096 men with questionnaire and genotype information from the Norwegian Mother, Father, and Child Cohort Study.
Intervention
Self-reported information on smoking (having ever smoked [both sexes], age at initiation [women only], cessation [women only], and cigarettes/week in current smokers [both sexes]) was gathered. Genetically predetermined levels or likelihood of presenting these traits were estimated for Mendelian randomization.
Main outcome measure
Infertility (time-to-pregnancy ≥12 months).
Results
Having ever smoked was unrelated to infertility in women or men. Higher smoking intensity in women was associated with greater infertility odds (+1 standard deviation [SD, 48 cigarettes/week]: odds ratio [OR]crude, 1.19; 95% confidence interval [CI] 1.11–1.28; ORadjusted 1.12; 95% CI, 1.03–1.21), also after adjusting for the partner’s tobacco use. Later smoking initiation (+1 SD [3.2 years]: ORcrude, 0.94; 95% CI, 0.88–0.99; ORadjusted 0.89; 95% CI, 0.84–0.95) and smoking cessation (vs. not quitting: ORcrude, 0.83; 95% CI, 0.75–0.91; ORadjusted, 0.83; 95% CI, 0.75–0.93) were linked to decreased infertility in women. Nevertheless, Mendelian randomization results were not directionally consistent for smoking intensity and cessation and were estimated imprecisely in the 2-sample approach. In men, greater smoking intensity was not robustly associated with infertility in multivariable regression and Mendelian randomization.
Conclusions
We did not find robust evidence of an effect of smoking on infertility. This may be due to a true lack of effect, weak genetic instruments, or other kinds of confounding.
Tabaquismo e infertilidad: regresión multivariable y análisis de aleatorización mendeliana en el estudio de cohorte noruego de madre, padre e hijo.
Document Type
Article
Document version
Published version
Language
English
Keywords
Hàbit de fumar
Esterilitat
Aleatorització Mendeliana
Pages
11 p.
Publisher
Elsevier
Is part of
Fertility and Sterility, 2022, 118(1): 180-190
Grant agreement number
info:eu-repo/grantAgreement/EU/H2020/Grant agreement 947684
This item appears in the following Collection(s)
Rights
© L'autor/a
Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by/4.0/