Elevated fasting insulin results in snoring: A view emerged from causal evaluation of glycemic traits and snoring

Snoring and impaired glucose metabolism are common clinical manifestations and associated. The purpose of our study is to estimate the causal associations between snoring and glycemic traits.

We compared the weighted mean differences (WMD) for fasting insulin (FINS), glycosylated haemoglobin (HbA1c), fasting blood glucose (FBG) and 2 h-glucose post-challenge (2hGlu) levels between snorers and non-snorers by meta-analysis. Then, we obtained summary statistics from published GWAS of snoring and glycemic traits to perform bidirectional two-sample MR. Inverse variance weighting (IVW) method was applied as major estimate while MR Egger, Weighted median and MR-Robust Adjusted Profile Score (RAPS) played a subsidiary role.

Snoring participants had higher FBG (WMD = 0.14 mmol/L, 95%CI = [0.10,0.19]), HbA1c (WMD = 0.10%, 95%CI = [0.07,0.13]), FINS (WMD = 0.92μIU/mL, 95%CI = [0.59,1.26]) and 2hGlu (WMD = 0.30 mmol/L, 95%CI = [0.06,0.55]) levels than non-snorers. Further, elevated FINS levels shown robust causal effect on snoring (IVW: OR = 1.07, 95%CI = [1.02,1.12], p = 2.2 × 10^-3 ), which was consistent by complementary methods of MR Egger (OR = 1.14, 95%CI = [1.01-1.30], p = 4.72 × 10^-2 ), Weighted median (OR = 1.11, 95%CI = [1.07,1.15], p = 1.53 × 10^-7 ) and MR RAPS (OR = 1.07, 95% CI = [1.05,1.10], p = 2.81 × 10^-9 ). Such causal situation was stable after identifying and removing the outliers in sensitivity analysis. However, there was no causality of snoring on increasing FINS levels. Additionally, there were no causal associations between snoring and other three traits of FBG, HbA1c and 2hGlu levels from either direction.

Snorers are subjected to higher FBG, HbA1c, FINS and 2hGlu levels, and elevated FINS levels further provides robust causality on snoring, suggesting that behind common snoring may lie hyperinsulinemia or insulin resistance.