Association between genetic risk scores and risk of narcolepsy: a case-control study

Genome-wide association studies (GWASs) have identified a large number of single-nucleotide polymorphisms (SNPs) associated with narcolepsy. However, the sum impact of these SNPs on defining the genomic risk of narcolepsy remains unknown. In the present study, we investigated the associations between genetic risk scores (GRSs) and narcolepsy along with their predictive power.

A case-control study consisting of 903 narcolepsy patients and 1,981 healthy control subjects was performed. Thirty-two SNPs previously reported to confer susceptibility to narcolepsy were assessed for their association with narcolepsy risk. Subsequently, we constructed four GRS groups comprising reported narcolepsy susceptibility SNPs located in different genomic regions, and tested their association with narcolepsy risk using a regression model. Receiver operating characteristic (ROC) curves were used to examine the discriminatory power of the GRSs for predicting narcolepsy.

Nine individual SNPs were significantly associated with narcolepsy after Bonferroni correction. All four GRSs were strongly associated with narcolepsy risk even when GRSs were constructed using SNPs located outside the previously implicated human leukocyte antigen (HLA) region on chromosome 6. The odds ratio (OR) for narcolepsy risk increased with the number of genetic loci implicated, ranging from an OR of 2.016 (95% CI, 1.657-2.456) to an OR of 4.298 (95% CI, 3.378-5.481). GRS4, constructed using the narcolepsy-associated SNPs identified in the Chinese population, was most closely associated with narcolepsy risk.

The results suggest that the GRS method for combining common genetic variations can significantly associate GRS scores with narcolepsy risk and may facilitate narcolepsy risk stratification for prevention trials, both for HLA-DQB1*06:02-positive and -negative individuals.