In a recent study published in The Lancet Regional Health, Researchers conducted a Mendelian randomization (MR) analysis to understand the causal effect of snoring on total stroke, hemorrhagic stroke (HS), and ischemic stroke (IS) among Chinese adults using data from the China Kadoorie Biobank (CKB).
Study: Causal association between snoring and stroke: a Mendelian randomization study in a Chinese population. Image credit: F01 PHOTO/Shutterstock.com
Record
MRI studies have assessed the relationship between snoring and stroke in the European population. However, these data for Asian populations are scarce, partly due to the unavailability of genetic variants, as revealed by the researchers’ extensive search in PubMed and Google Scholar.
A few observational studies have assessed the relationship between snoring and stroke in people of different ethnicities, but their findings have been inconclusive.
Here, it is worth noting that snoring can cause stroke through several pathways. For example, it can cause anoxemia, resulting in oxidative stress responses and endothelial disruption, which can ultimately lead to atherosclerosis and stroke.
Similarly, snoring can transmit a high-level vibration to the carotid artery, causing a cascading effect on the cells of the arterial wall that can result in vessel rupture.
About the study
In the present study, based on single nucleotide polymorphisms (SNPs) from genome-wide association analysis (GWAS) of snoring among CKB and UK Biobank participants, researchers constructed genetic risk scores (GRS).
They used these data to causally link snoring to stroke among Chinese adults aged 30–79 living in ten study areas across China.
Multivariable MR (MVMR) included additional adjustments for body mass index (BMI) GRS and used SNPs from CKB, UKB and Biobank Japan.
Study participants self-reported their snoring status in the baseline survey, with those who reported frequent or occasional snoring classified as snorers and others as non-snorers.
The three study outcomes were incident stroke, HS and IS. The researchers confirmed the validity of the registry and insurance definition of stroke events by reviewing medical records and achieving a diagnosis confirmation rate of 91.8%.
During the statistical analysis, the team used the Efron pseudo-R2 and eat statistics to estimate the variance explained by the GRS for snoring. Similarly, they used a two-step method to determine the causal hazard ratio (HR), adjusting for multiple factors.
In addition, the team used MRI with the inverse variance weighting (IVW) method to examine the causal effect of snoring and stroke, using three SNPs identified in the CKB GWAS as genetic instrument variables (IVs) for snoring.
They checked for pleiotropy and heterogeneity via MR-Egger regression and Cochrane’s Q tests. Sensitivity analysis excluded SNPs associated with adiposity.
Results and conclusions
The present MRI analysis of snoring and stroke included 82,339 unrelated participants of Asian origin in CKB with reference and genotype data.
During a mean follow-up of 10.10 years, 19,623 had strokes, with 11,483 cases of IS and 5,710 cases of HS. MR‒Egger regression test showed no horizontal pleiotropy (P>0.05) and Cochrane’s Q test showed no heterogeneity (P>0.05).
Results confirmed a positive association between snoring and total stroke, as well as HS and IS, with respective HRs (95% CIs) of 1.56, 1.50, and 2.02 using GRS of 100,626 CKB participants. Similarly, the corresponding HRs using the UKB GRS were 1.78, 1.94 and 1.74.
Due to obesity, i.e. the deposition of fat in the structures near the upper airway or the tongue, snoring occurs. Accordingly, some studies have shown that oropharyngeal exercises and mandibular advancement devices can treat snoring.
In the present study, the researchers conducted several sequential analyzes to address the confounding bias introduced by obesity.
However, they observed that these associations remained stable during MVMR analysis, MRI analysis using the IVW method, and MRI among the non-obese group (BMI<24.0 kg/m2), suggesting that BMI pleiotropy did not influence the causative effect of snoring on stroke.
Thus, they concluded that snoring interventions aimed at managing physical structure could be more beneficial than weight management for stroke prevention.
Overall, this study found snoring as a potential causative factor for increased risk of stroke and its subtypes among Chinese adults, which remained stable regardless of the effect of BMI, a well-established risk factor for stroke.
