Insomnia and impacts on facial expression recognition accuracy, intensity and speed: A meta-analysis

Facial expressions provide nonverbal cues that are important for delivering and interpreting human emotions. Previous studies have shown that the ability to interpret facial emotions correctly could be partially impaired in sleep-deprived people. People with insomnia might also suffer from sleep loss, so we assumed that facial expression recognition ability might also be impaired in people with insomnia. Despite a growing body of research exploring insomnia's potential impacts on facial expression recognition, conflicting results have been reported, and no systematic review of this research body has been conducted. In this study, after screening 1100 records identified through database searches, six articles examining insomnia and facial expression recognition ability were included in a quantitative synthesis. The main outcomes were classification accuracy (ACC), reaction time (RT), and intensity rating-the three most studied facial expression processing variables. Subgroup analysis was performed to identify altered perceptions according to the facial expressions of four emotions-happiness, sadness, fear, and anger-used to examine insomnia and emotion recognition. The pooled standard mean differences (SMDs) and corresponding 95% confidence intervals (CIs) demonstrated that facial expression recognition among people with insomnia was less accurate (SMD = -0.30; 95% CI: -0.46, -0.14) and slower (SMD = 0.67; 95% CI: 0.18, -1.15) compared to good sleepers. The classification ACC of fearful expression was lower in the insomnia group (SMD = -0.66; 95% CI: -1.02, -0.30). This meta-analysis was registered using PROSPERO.