Safety implications of mask use: A systematic review and evidence map

Background Widespread use of respiratory protection masks has become a critical component of public health response. Objectives This systematic review synthesises the evidence on the acute physiological, cognitive and psychological impacts associated with different types of masks and provides an evidence map of research gaps. Methods A comprehensive search from 2000 to 2023 was conducted across multiple databases (MEDLINE, EMBASE, Cochrane databases, Scopus and PubMed). An umbrella systematic overview was conducted for physiological outcomes using existing systematic reviews. We conducted de novo systematic reviews for cognitive and psychological outcomes. Pairs of independent reviewers determined eligibility, extracted data and assessed risk of bias. Certainty at an outcome level was appraised using the Grading of Recommendations Assessment, Development and Evaluation approach. Results The search resulted in 13 370 potential citations, leading to the inclusion of nine systematic reviews for physiological outcomes (87 primary studies) and 10 primary studies for cognitive and psychological outcomes (3815 participants), with the majority of participants being healthy adults. Studies evaluating physiological outcomes demonstrated that various types of masks have little to no significant difference in heart rate (surgical mask (mean difference (MD): 0.96 (-1.01 to 2.93)), N95 mask (MD: 1.63 (-2.79 to 6.05)) and cloth mask (MD: -0.94 (-6.39 to 4.52))) or respiratory rate during rest or exercise (surgical mask (MD: -1.35 (-3.00 to 0.29)), N95 mask (MD: 0.10 (-3.10 to 3.29)) and cloth mask (MD: -2.57 (-6.44 to 1.29)) (low certainty for most outcomes)). Mask use may be associated with very small changes in minute ventilation (surgical mask (MD: -13.9 (-20.30 to -7.53)) and N95 mask (MD: -16.3 (-28.7 to -3.9))), tidal volume (surgical mask (MD: -0.14 (-0.23 to -0.05)) and N95 mask (MD: -0.10 (-0.33 to 0.13))), oxygen saturation (surgical mask (MD: -0.59% (-0.87 to -0.30)), N95 mask (MD: -0.35% (-0.75 to 0.05)) and cloth mask (MD: -0.50% (-1.23; 0.24))), carbon dioxide partial pressure (surgical mask (standardised MD (SMD): 1.17 (0.70 to 1.64)) and N95 mask (SMD: 0.43 (0.08 to 0.79))) and exercise performance (surgical mask (SMD: -0.12 (-0.39 to 0.15)), N95 mask (SMD: -0.42 (-0.76 to -0.08)) and cloth mask (SMD: -0.26 (-0.54 to 0.02)) (low certainty for most outcomes)). Studies evaluating cognitive outcomes showed mixed results. Some studies reported reduced mental workload, and others showed no significant effect or decreased performance. The impact on attention, errors and reaction time was variable. These studies were small and at moderate to high risk of bias. Evidence was insufficient to estimate the effect of mask use on psychological outcomes (claustrophobia, depression and anxiety) as these studies were small, non-longitudinal and at high risk of bias. Conclusion This evidence map provides a comprehensive insight into the multifaceted impact of respiratory protection mask use, and highlights the limited certainty in the available body of evidence. This evidence map supports the development of future research agenda.