COVID-19, which started in Wuhan, China in December and spread rapidly around the world, was declared a pandemic by the World Health Organization in March 2020 and has been observed in our country since March 2020. Since the disease is transmitted through respiratory droplets, it is necessary to use masks and personal protective equipment. In particular, the long-term exposure of healthcare workers to masks and personal protective equipment can cause many complaints such as acne, skin breakdown, impaired cognition, and headache [1]. There are several studies showing the emergence of a new headaches due to the use of masks in healthcare workers [2-4]. The aim of this study is to investigate mask-related headache during the COVID-19 outbreak, and to determine its clinical features.

This study was carried out at the Afyonkarahisar Health Sciences University between November 15 and December 15, 2020. It was performed on doctors, nurses, and other healthcare professionals working at the hospital.

A total of 380 healthcare professionals were invited to participate in this study, and 375 accepted, for a participation rate of 98.7%. One hundred sixty-one (42.9%) of the participants were male, and 214 (57.1%) of them were female. The median age of the study participants was 32 (interquartile range [IQR]: 12, range 21-65). Seventy-eight (20.8%) of the participants were doctors, 103 (27.5%) were nurses, and 194 (51.7%) were other healthcare workers. One hundred five (28.0%) of them were working in the COVID clinic and COVID intensive care unit (ICU), while 270 (72.0%) were working in the polyclinic and other departments. Comorbidity was present in 29 (7.7%) of all screened healthcare workers. Table 1 summarizes the characteristics of the healthcare workers.

Twenty-six (6.9%) person used filtering masks, 274 (73.1%) used surgical masks, and 75 (20.0%) used both masks in combination. Mask use duration was between 1-4 hours in 29 healthcare workers and more than 4 hours in 346 healthcare workers (Table 2). One hundred four (27.7%) of them were using other protective equipment including eyeglasses. Seventy-eight (20.8%) were using other protective equipment other than eyeglasses. One hundred ninety-three (51.5%) of them were not using other protective equipment.

Pre-existing headache was recorded in 114 (30.4%) healthcare workers. Seventy-nine of them were female and 35 were male. Pre-existing headache in female was statistically significantly higher (P = 0.002). Pre-existing headache type was migraine in 43 (37.7%), tension headache in 68 (59.6%), and other headaches in 3 healthcare workers (2.6%) (Table 3). The pre-existing headache median frequency was 3 (IQR: 3), and the visual analogue scale (VAS) score was 5 (IQR: 3). Seventy-seven (67.5%) of those with pre-existing headache had an aggravation in headache after mask use. There was an aggravation in headache in 7.7% in those who used filtering masks, in 19% of those using surgical masks, and in 30.7% of those who used both in combination. There was a statistically significant aggravation in headache in those who used both masks in combination (P = 0.021). There was no significant correlation between the duration of mask use and the aggravation in headache (P = 0.350). There was no significant correlation between the department and duty of the individuals and the aggravation in headache (P = 0.067 and P = 0.133, respectively). There was an aggravation in headache in 27 (26.0%) of those using other protective equipment including eyeglasses, in 15 (19.2%) of those using other protective equipment except eyeglasses, and in 32 (16.6%) of those who were not using other protective equipment. There was no significant relationship between the use of other protective equipment including eyeglasses and aggravation in headache (P = 0.133). The median frequency of those with aggravated headache was 6 (IQR: 12), and the VAS score was 6 (IQR: 7). There was a statistically significant increase in frequency and VAS scores (P < 0.001 and P = 0.019, respectively). There was an increase in analgesic drug use in 55 healthcare workers (48.2%). No significant relationship was observed between type of mask and the duration of mask use and analgesic drug increase (P = 0.069 and P = 0.075, respectively).

De-novo headache was recorded in 116 (30.9%) healthcare workers. De-novo headaches were detected in 50.0% of those who used filtering masks, in 25.9% of those using surgical masks, and in 42.7% of those who used both in combination. A significant relationship was found between the type of mask and new headache (P = 0.002). No relationship was found between mask use duration and de-novo headache (P = 0.097). De-novo headache was recorded in 42 (40.4%) of those using other protective equipment including eyeglasses, in 22 (28.2%) of those using other protective equipment except eyeglasses, and in 52 (26.9) of those who were not using other protective equipment. A significant relationship was found between the use of other protective equipment including eyeglasses and de-novo headache (P = 0.048). De-novo headache was observed in 41.9% of COVID clinic and ICU workers, and in 26.7% of workers in other departments. A significant relationship was found between the department of employment and de-novo headache (P = 0.004). There was no significant relationship between task and de-novo headache (P = 0142). De-novo headache characteristics were throbbing in 17 (14.7%) healthcare workers, pressing in 99 (85.3%), unilateral in 12 (10.3%), and bilateral in 104 (89.7%) (Table 4). The median frequency of de-novo headache was 8 (IQR: 7), and the VAS score was 5 (IQR: 2). De-novo headache areas are shown in Fig. 1. Accompanying symptoms are sleep disorder, fatigue, tachypnea, dizziness, nausea, and palpitations (Table 4). The median value of the onset of headache after wearing a mask was 1 (IQR: 2), and the median value of headache resolution time after mask removal was 2 (IQR: 3).

The results of this study indicate that during the COVID-19 outbreak, a new type of headache has developed among healthcare workers. Both an aggravation in pre-existing headaches and the emergence of de-novo headaches has been shown to increase with mask use, regardless of mask use duration. This rate increases even more when both masks are used in combination. A de-novo headache is characterized by a bilateral, moderate, and pressing nature. The clinical characteristics of a de-novo headache are more like a tension headache, however, it has also some accompanying symptoms, such as throbbing and unilateral characteristics similar to migraines. The new type headache starts shortly after putting on the mask and disappears after removing it. In addition, sleep disorder, fatigue, and tachypnea were also observed at a high rate.

Rosner [1] reported the adverse effects of long-term mask use on healthcare workers, and headache was the most common complaint observed, at a rate of 71.4%.

The number of studies on headache associated with mask use is very limited [2-4]. Several studies have described mask-associated de-novo headache [2,3]. It was reported that a significant increase was observed in headaches in people with pre-existing headache as well as an increase in analgesic drug use and a significant relationship was found between the use of other protective equipment, including goggles, and de-novo headache [2]. An another study reported that an increase was observed in pre-existing headache and work stress after mask use. In the same study, work stress was found to be higher in patients with de-novo headache than those without headache [3]. In our study, the effect of work stress on headache could not be determined because an evaluation was not made regarding work stress.

There may be more than one mechanism in the physiopathology of de-novo headache. Several factors may explain its association with the use of filtering masks, including hypoxia, hypercapnia, local compression, and even mask use anxiety [4]. Sleep deprivation, irregular mealtimes, and emotional stress are other sources of headache among healthcare workers during prolonged mask use [2].

Tight-fitting masks cause insufficient ventilation, and cause the level of carbon dioxide (CO₂) to rise. CO₂ is known as a respiratory stimulant, and inhalation of CO₂ between the mask and the face causes increased respiratory activity [5]. In our study, the significantly higher incidence of de-novo headache in filtering mask users supports that CO₂ inhalation may be a reasonable etiology. The fact that the highest aggravation in pre-existing headache was found in those who use a filter mask and surgical mask together supports this theory; but it is higher in those who use only surgical masks than in those who use only filtered masks, suggesting that there may be other factors besides CO₂ inhalation. In a study of 130 astronauts exposed to high CO₂ pressures during controlled training, the exposed group showed a significantly higher incidence of headache, in addition to respiratory symptoms and difficulty concentrating [6]. Another mechanism that can explain headache physiopathology may be external compression [7]. In our study, de-novo headache was more common in those who wear eyeglasses.

The limitations of this study are that other predisposing factors that may contribute to the development of de-novo headaches such as stress, nutrition, and sleep disorders were not evaluated.

The strengths of this study are that the study was conducted by neurologists who filled out the questionnaires face to face with the participants.

In conclusion, this study illustrates that mask use among healthcare workers during the COVID-19 outbreak causes de-novo headaches. The characteristics of the de-novo headache are similar to tension-type headache. Better strategies are needed to reduce the duration of exposure to personal protective equipment so that healthcare workers’ job performance and quality of life are less affected. Shorter duty shifts and correspondingly shorter durations of personal protective equipment use may well be a good strategy to avoid the negative effects of using such equipment.