Causal relationships between four types of sedentary behavior and insomnia: a two-sample Mendelian randomization...

This study utilized a two-sample Mendelian randomization (MR) approach to investigate the causal relationships between specific sedentary behaviors-namely, driving, watching television, using a mobile phone, and using a computer-and insomnia.

We selected independent genome-wide significant SNPs for each exposure and harmonized them with the insomnia GWAS. GWAS summary statistics were obtained from IEU OpenGWAS (UK Biobank). Instrument selection used P < 5 × 10⁻⁸ and LD clumping at r² < 0.001, 10,000 kb. Primary MR estimates were obtained using inverse variance weighting (IVW), with weighted median and MR-Egger as complementary methods. Sensitivity analyses included Cochran's Q, MR-Egger intercept, MR-PRESSO, and leave-one-out.

After harmonization, the numbers of independent SNPs were: driving (n = 6), television (n = 104), mobile phone (n = 31), and computer (n = 80). IVW MR showed a positive association between television watching and insomnia (OR = 1.20, 95% CI: 1.15-1.26, P < 0.001). Driving showed an inverse association with insomnia (OR = 0.821, 95% CI: 0.72-0.94, P = 0.005). Computer and mobile phone use did not show statistically significant IVW associations with insomnia. Sensitivity analyses did not indicate consistent directional pleiotropy; leave-one-out did not identify any influential SNP.

Our MR results indicated that genetic liability to longer television-watching time is associated with an increased risk of insomnia, whereas genetic liability to longer driving time is associated with a decreased risk of insomnia. It is important to approach these results carefully, as the genetic tools employed in this research mainly reflect a behavior's general duration or tendency, lacking specific contextual information or timing nuances.