Background: As face masks are a mandatory public health intervention during the COVID-19 pandemic, adverse effects require substantiated investigation.
Methods: A systematic review of 2168 studies yielded 54 publications for synthesis and 37 studies for meta-analysis (on n=8641, m=2482, f=6159, age=34.8±12.5). The median trial duration was only 18 min (IQR=50) for our comprehensive evaluation of mask induced physio-metabolic and clinical outcomes.
Results: We found significant effects in both medical masks with a greater impact regarding the N95. These effects included decreased SpO2 (overall SMD=-0.24, 95%CI=-0.38 to -0.11, p=0.0004) and minute ventilation (SMD=-0.72, 95%CI=-0.99 to -0.46, p<0.00001), simultaneously increased blood-CO2 (SMD=+0.64, 95%CI=0.31–0.96, p=0.0001), heart rate (N95: SMD=+0.22, 95%CI=0.03–0.41, p=0.02), systolic blood pressure (surgical: SMD=+0.21, 95%CI=0.03–0.39, p=0.02), skin temperature (overall SMD=+0.80 95%CI 0.23–1.38, p=0.006) and humidity (SMD +2.24, 95%CI=1.32–3.17, p<0.00001). Effects on exertion (overall SMD=+0.9, surgical=+0.63, N95=+1.19), discomfort (SMD=+1.16), dyspnoea (SMD=+1.46), heat (SMD=+0.70) and humidity (SMD=+0.9) were significant in 373 cases with a robust relationship to mask wearing (p<0.006 to p<0.00001). Pooled symptom prevalence was significant in users (n=8128) for: headache (62%, p<0.00001), acne (38%, p<0.00001), skin irritation (36%, p<0.00001), dyspnoea (33%, p<0.00001), heat (26%, p<0.00001), itching (26%, p<0.00001), voice disorder (23%, p<0.03) and dizziness (5%, p=0.01).
Discussion: Masks interfered with O2-uptake and CO2-release and compromised respiratory compensation. Though evaluated wearing durations do not represent daily/prolonged use, outcomes independently validate mask-induced exhaustion-syndrome (MIES). MIES can have long-term clinical consequences, especially for vulnerable groups.
Conclusion: Face mask side-effects must be assessed (risk-benefit) against the available evidence of their effectiveness against viral transmissions.