Elucidating the causal role of age of menarche, adiposity, lipid fractions, and blood pressure upon cardiovascular disease: A multivariable Mendelian randomization study

This study evaluates the potential role of multiple correlated risk factors upon coronary heart disease (CHD) and ischemic stroke, and the extent to which using GWAS summary data including prevalent cases of stroke, as opposed to incident cases, can influence Mendelian randomization (MR) analyses. Initially, thirteen candidate risk factors were identified through a literature review, including age of menarche, adiposity, blood pressure, lipid fractions, physical activity, type-II diabetes, smoking, sleep duration, alcohol consumption, and kidney function. Using publicly available summary data from genome-wide association studies (GWAS), the total effect of each exposure on CHD, ischemic, and cardioembolic stroke was estimated using univariable summary MR. Multivariable MR (MVMR) analyses were then used to estimate the conditional effects of low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides and systolic blood pressure (SBP) on each outcome. To select the MVMR model a novel forward selection algorithm was applied to include the greatest number of exposures while maintaining sufficient conditional instrument strength for estimation. To examine potential bias from using GWAS summary data derived from prevalent cases of ischemic stroke a GWAS of incident ischemic stroke was conducted using data from the UK Biobank. In univariable MR analyses negative effects of blood pressure were observed across all outcomes, while the effects of remaining exposures differed markedly. HDL was also estimated to have a protective effect on all outcomes except cardioembolic stroke. Univariable and MVMR estimates were directionally consistent, though MVMR estimates were attenuated. Finally, repeating analyses using incident stroke cases yielded results in agreement with prevalent stroke data, suggesting the use of prevalent outcome data did not bias our initial analysis. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by The Wellcome Trust (108902/B/15/Z) and UK Medical Research Council Integrative Epidemiology Unit at the University of Bristol (MC UU 00011/2, MC UU 00011/1). In addition, this research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: HI21C1243), and the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. RS-2023-00210888). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: UK Biobank has approval from the North West Multi-centre Research Ethics Committee (MREC) as a Research Tissue Bank (RTB) approval. This approval means that researchers do not require separate ethical clearance and can operate under the RTB approval (there are certain exceptions to this which are set out in the Access Procedures, such as re-contact applications). See for more information. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Not Applicable The paper predominantly uses GWAS summary data which is publicly accessible from , and extracted using code provided. In addition the paper uses GWAS summary data obtained using incident stroke data from the UK Biobank. Summary data for this GWAS is available online at , including code for replicating analyses. Access to individual data needed to conduct a GWAS of incident ischemic stroke can be obtained by submitting an application to .