Exposure duration and cybersickness in head-mounted displays: A meta-analysis of threshold effects across virtual and extended reality

Head-mounted displays (HMDs) are increasingly used in entertainment, education, industry, and clinical training, yet guidance on continuous exposure remains inconsistent. Because devices, optics, content motion, locomotion, and symptom definitions vary widely, the current evidence does not support a single universal biological threshold. We conducted a meta -analysis of experimental studies in healthy adults reporting post-exposure Simulator Sickness Questionnaire (SSQ) total scores and a conclusive binary outcome for significant HMD-induced symptoms. Using arm-level data, we performed random-effects meta -regression of SSQ on exposure duration and pooled SSQ estimates across prespecified duration bins (≤15, 15–30, and >30 min). For secondary classification analyses, we evaluated duration cut-offs for predicting binary symptom outcomes using receiver operating characteristic (ROC) curves and Youden’s index. Twenty-eight studies met the inclusion criteria, with subsets contributing to SSQ-based and symptom-based analyses depending on outcome availability. Post-exposure SSQ tended to be lower at shorter durations and higher at longer durations. In random-effects meta -regression, exposure duration showed a modest but statistically significant positive association with post-exposure SSQ Total score (slope, 0.308 SSQ points/min; 95% confidence interval, 0.012 to 0.605; p = 0.041), although between-arm heterogeneity remained non-trivial. The fitted regression line crossed a practical SSQ reference value of 25 at approximately 26 min. ROC analysis yielded moderate discrimination at a 32.5-minute threshold, positioning exposure duration as a practical screening metric rather than a definitive, standalone safety limit. Prospective studies with standardized protocols, time-resolved symptom measurements, and better control of device- and task-specific factors are needed to refine exposure guidance.