FFP2 protective masks have no or few effects on bodily metrics such as heart rate, blood oxygen saturation, or heart rate variability, including during physical activity. But what about their impact on mental performance? A team from Technische Universität Berlin investigated this in a controlled experiment with 44 randomly selected participants. It determined that test subjects were equally able to manage a stressful situation completing mental math problems whether wearing a mask or not. All measured vitals also remained the same. In addition, participants indicated that their mental stress remained unchanged when wearing a mask. The results of the study have been published in Nature Scientific Reports.
FFP2 masks effectively prevent Sars-CoV-2 infection. This new use of masks, which were originally designed for occupational health protection, has led to many studies investigating their potential impact on the human body . "If you look at the major reviews that have evaluated a large number of studies, the picture is clear. In fact, wearing masks even under physical stress leaves vital signs virtually unchanged," says Robert Spang of the Quality and Usability Lab at TU Berlin and first author of the paper. “However, particularly indoors, such as in offices or schools, where the risk of transmission through aerosols is especially high, most individuals perform mental, not physical tasks.”
In order to bridge this knowledge gap about working conditions when wearing FFP2 masks, Robert Spang and his co-author Kerstin Pieper drew on their experiences in the Quality and Usability Lab, which has researched human-machine interactions for nearly 15 years. "For example, we are very familiar with how to place people under stress," explains Pieper. In order to produce mental stress, subjects had to complete numerous arithmetic equations (addition, subtraction, multiplication, or division) with integers up to 200 and enter the solution on a smartphone. "We also had a program running in the background which estimated how much time each test subject would require for the next problem based on the previous one." The estimated time was then set as the time limit and displayed as a shrinking progress bar. "Every participant was pushed to their personal performance limit as much as possible."
Significant consideration and preparation went into designing the study to achieve the most meaningful results. "We applied a statistical procedure which could directly evaluate our hypothesis that cognitive performance remains unaffected," says Pieper. "This is different than simply demonstrating that a change is not statistically verifiable." Prior to their experiment, the researchers calculated the criteria necessary to be statistically significant and published these on an independent research platform online. "This procedure, which is not yet established in research, ensures that researchers cannot amend data and findings to their benefit," emphasizes Pieper. The scientists also used statistical methods to determine the number of test subjects needed to make reliable conclusions before the experiment.
For the study, 44 male and female subjects were randomly selected from 3,500 volunteers in a test person database at TU Berlin. Comparisons of their math results when wearing a mask or not showed that the mask had no impact on subjects' abilities. The vitals measured during the mental exercise – blood oxygen saturation, heart rate, and heart rate variability, that is how the time between heartbeats changes on average – also remained unchanged. A change to a lower variability would have been an indicator of ongoing stress. Participants were also asked to subjectively assess their mental stress using a questionnaire developed by NASA. These results also did not show a difference between the math problems completed with and without a mask.
"From our other experiments on human-machine interaction, we know that a 5-minute time frame is adequate to observe physical and mental reactions to external stimuli," explains Spang. To be sure, participants were even tested with the math problems for fifteen minutes each, once without a mask and once with a mask, and only the results of the last five minutes of these stress phases were evaluated. According to Spang, however, it is important not to conflate the results of the study with subjective perceptions of physical changes. "Other studies demonstrate, for example, that our breathing rhythm changes when we have an additional air space in front of our mouth and nose," he explains. "Due to the buildup of warm air, you may feel as well that you have an increased temperature." Such perceptions however do not impact the actual values of lung function or body temperature.
 Large overview study on the effects on vitals, including during physical activity: https://www.atsjournals.org/doi/10.1513/AnnalsATS.202008-990CME
Link to study by Robert Spang and Kerstin Pieper on the effects of wearing a mask under mental stress: https://www.nature.com/articles/s41598-021-99100-7