Results
A total of 306 health professionals and other health workers participated in the study, 62 men (20.3%) and 244 women (79.7%), with an average age of 43 years (SD: 11; range: 23–65). Of these, 129 (42.2%) participants were physicians, 112 (36.6%) nurses and the rest, 65 (21.2%) other health workers (assistants, guards, technicians, administrative staff). With regard to the work shift, 89 (34.1%) worked in the morning and on duty, 91 (34.9%) at morning, afternoon and night shifts, and 81 (31.0%) in morning shifts only. The surgical mask was used by 208 (79.7%) of those surveyed, and the filter mask (FFP2 or KN95) was used by 53 (20.3%), with no difference in the mean time of use 7.0 (SD: 2.3) hours vs 6.7 (SD: 2.5) hours, p=0.289. A total of 46.4% (121) reported not habitually using other facial protection devices such as glasses, screens or PPE. The rate of confirmed SARS-CoV-2 infection in the study population was 4.6%.
The most frequently reported diseases in the total sample in order of frequency were: allergy, 34 (13.0%); thyroid diseases, 28 (10.7%); anxiety, 26 (10.0%); high blood pressure, 18 (6.9%); asthma, 17 (6.5%); dyslipidaemia, 14 (5.4%) and diabetes, 2 (0.8%). A total of 15.7% (41) indicated tobacco consumption.
Of the 306 persons surveyed, 158 (51.6%) reported the appearance of a new headache during the period of study, of whom 65 (41.1%) had previously had a headache (migraine: 27 (17.1%), tension: 26 (16.5%) and others: 11 (6.9%)). There were 103 (33.7%) subjects who did not observe the appearance of a new headache. A 14.7% were undecided on the answer ‘I don't know’ or the answer was ‘maybe’; these 45 subjects were eliminated from the analysis.
They were also asked about the presence of other symptoms such as sleep disturbance, loss of concentration, irritability, photophobia, sonophobia, nausea or vomiting. Table 1 shows the characteristics of the population.
Table 1  Baseline conditions and mask and Personal Protective Equipment (PPE) usage among healthcare workers
Total  De novo headache  P value
No  Yes
N= 261  (n=103)  (n=158)
Age, years (SD)  42.9 (10.7)  40.8 (11.4)  44.4 (10.1)  0.009
Female gender  208 (79.7%)  73 (31.1%)  135 (64.9%)  0.004
Occupation    0.0001
 Doctor  112 (42.9%)  61(54.5%)  51 (45.5%)
 Nurse  95 (36.4%)  33 (34.7%)  62(65.3%)
 Others  54 (20.7%)  9(16.7%)  45(83.3%)
Work shift    <0.0001
 Mornings and 24-hour duties  89 (34.1%)  51 (57.3%)  38 (42.7%)
 Rotating shifts  91 (34.9%)  26 (28.6%)  65 (71.4%)
 Others  81 (31.0%)  26 (32.1%)  55 (67.9%)
Type of face mask    0.029
 Surgical mask  208 (79.7%)  89 (42.8%)  119 (57.2%)
 N95/FFP2  53 (20.3%)  14 (26.4%)  39 (73.6%)
Number of hours worn per day (SD)  6.9 (2.3)  6.8 (2.4)  7.0 (2.2)  0.474
Use of another PPE:    0.203
 Face shield  54 (20.7%)  21 (38.9%)  33 (61.1%)
 Protective eyewear  33 (12.6%)  13 (39.4%)  20 (60.6%)
 Complete PPE  46 (17.6%)  16 (34.8%)  30 (65.2%)
Confirmed COVID-19  12 (4.6%)  4 (33.3%)  8 (66.7%)  0.161
Pre-existing headache  110 (42.1%)  45 (40.9%)  65 (59.1%)  0.683
Comorbidity
 Allergy  34 (13.0%)  16 (47.1%)  18(52.9%)  0.331
 Asthma  17 (6.5%)  11 (64.7%)  6 (35.3%)  0.028
 Tobacco  41 (15.7%)  8 (19.5%)  33 (80.5%)  0.004
 Arterial hypertension  18 (6.9%)  9 (50.0%)  9 (50.0%)  0.789
 Cardiopathy  1 (0.4%)  0 (0.0%)  1 (100%)  0.419
 Dyslipidaemia  14 (5.4%)  7 (50.0%)  7 (50.0%)  0.76
 Diabetes  2 (0.8%)  1 (50.0%)  1 (50.0%)  0.76
 Thyroid disease  28 (10.7%)  9 (32.1%)  19 (67.9%)  0.402
 Anxiety  26 (10.0%)  6 (23.1%)  20 (76.9%)  0.072
 Others  16 (6.1%)  4 (25.0%)  12 (75.0%)  0.222
Other symptoms
 Sleep disturbance  79 (30.3%)  11 (13.9%)  68 (86.1%)  0.0001
 Loss of concentration  73 (28.0%)  14 (19.2%)  59 (80.8%)  0.0001
 Irritability  74 (28.4%)  18 (24.3%)  56 (75.7%)  0.002
 Photophobia  31 (11.9%)  8 (25.8%)  23 (74.2%)  0.097
 Sonophobia  24 (9.2%)  6 (25.0%)  18 75.0%)  0.128
 Sickness/vomiting  24 (9.2%)  11 (45.8%)  13 (54.2%)  0.503
FFP2, filtering face pieces; N95, 95% particle filtering capacity. During April, the month prior to the survey, participants with ‘de novo’ headache presented a median of 12 (IQR: 13) days of headache, median of 4 (IQR: 3) days in the week prior to the survey, and the pain presented an average intensity on the Visual Analogue Scale (VAS) of 6 (SD: 1.5). In 74 (47.4%) subjects, the duration was from 1 to 4 hours; in 46 (29.5%), from 4 to 8 hours; in 21 (13.5%), from 8 to 12 hours; and in 15 (9.6%), more than 12 hours. In subjects with previous headache, the duration of episodes was significantly higher (p=0.008). The response to analgesics was good or very good in 61.4% of the cases. Only two (1.3%) subjects had to consult the emergency department for headache, and no subject had been admitted to hospital. With respect to the impact of headache in the work setting, lack of concentration on tasks was the main report (105 (66.5%) subjects). Table 2 shows the main characteristics of ‘de novo’ headache.
Table 2  Characteristics of headache in healthcare worker (HCW) mask users
All HCW with de novo headache  HCW without pre-existing headache  HCW with pre-existing headache  P value
(n=158)  (n=93)  (n=65)
Days with headache/month (SD)  13.2 (7.2)  13.0 (7.4)  13.5 (7.1)  0.746
Days with headache/week (SD)  3.8 (1.7)  3.8 (1.7)  3.9 (1.7)  0.827
Mean pain level, VAS (SD)  5.9 (1.5)  5.8 (1.5)  6.1 (1.4)  0.08
Duration time (hours)    0.008
 1–4  74 (47.4%)  52 (57.1%)  22 (33.8%)
 4–8  46 (29.5%)  23 (25.3%)  23 (35.4%)
 8–12  21 (13.5%)  12 (13.2%)  9 (13.8%)
 >12  15 (9.6%)  4 (4.4%)  11 (16.9%)
Analgesic response    0.342
 Good or very good  97 (61.4%)  61 (65.6%)  36 (55.4%)
 Regular  46 (29.1%)  23 (24.7%)  23 (35.4%)
 Bad or very bad  15 (9.5%)  9 (9.7%)  6 (9.2%)
Headache impact on HCW (SD)
 Occupational  4.0 (2.6)  3.5 (2.6)  4.6 (2.5)  0.02
 Family  4.4 (2.7)  4.1 (2.6)  4.9 (2.5)  0.084
 Personal  5.0 (2.6)  4.7 (2.7)  5.5 (2.4)  0.049
 Social  4.8 (2.8)  4.4 (2.8)  5.4 (2.7)  0.021
SD, Standar Deviation; VAS, Visual Analogue Scale. Of the 65 subjects with a previous headache, 83.1% (54) indicated a modification in the characteristics of their habitual headaches, 81.0% (47) a change in location, 67.2% (39) in frequency, 36.2% (21) in intensity and 25.9% (15) in the response to habitual analgesics.
In the univariate analysis, the factors associated with the appearance of ‘de novo’ headache were age, female sex, type of profession, use of filter mask (KN95 or FFP2), work shift, being a tobacco user, suffering from anxiety or asthma. In the multivariate analysis, the use of filter masks and the type of profession behaved as independent predictors of headache risk, while being asthmatic behaved as a protective factor. The occurrence of headache is associated with the use of a filter mask (FFP2 or KN95), OR 2.14 (95% CI 1.07 to 4.32); being a health worker, OR 6.94 (95% CI 3.01 to 16.04) or a nurse, OR 2.09 (95% CI 1.18 to 3.72) (table 3).
Table 3  Univariate and multivariate analysis of factors of baseline conditions
Variables  Univariate analysis  Multivariate analysis
OR  95% CI  P valúe  OR  95% CI  P valúe
Age  1.03  1.01 to 1.06  0.009
Female gender  2.41  1.31 to 4.45  0.005
Doctor  Ref  Ref  0.0001  Ref  Ref  <0.0001
Nurse  2.25  1.28 to 3.94   2.09  1.18 to 3.72
Other HCW  5.98  2.67 to 13.4   6.94  3.01 to 16.04
Filter mask versus surgical  2.08  1.07 to 4.07  0.026  2.14  1.07 to 4.32  0.027
Mornings and 24-hour duties  Ref  Ref  0.0001
Rotating shifts  3.35  1.81 to 6.23
Other work shifts  2.83  1.52 to 5.32
Asthma  0.33  0.12 to 0.92  0.03  0.29  0.09 to 0.89  0.026
Tobacco  3.13  1.39 to 7.01  0.003
Anxiety  2.34  0.91 to 6.05  0.063
95%CI, 95% Confidence Interval; HCW, healthcare workers; HCW, healthcare worker; OR, odds ratio; Ref., Reference category. According to the type of mask used, there was no difference in the number of days with headache in the month prior to the survey, 13.4 (SD: 7.4) vs 12.6 (SD: 6.9); nor in the previous week, 3.9 (SD: 1.6) vs 3.6 (SD: 1.7); but in the intensity according to VAS, 5.7 (SD: 1.5) vs 6.5 (SD: 1.2), p=0.004.
The impact of headache in subjects with a filter mask as opposed to surgical mask was worse in the four aspects evaluated by the Likert scale: occupational, 4.44 vs 3.81 (p=0.206); family, 5.10 vs 4.20 (p=0.065); personal, 5.64 vs 4.84 (p=0.05) and social, 5.46 vs 4.58 (p=0.076) (figure 1). The impact was also greater in subjects with a previous headache in the four aspects evaluated (table 2).
Figure 1  Impact of headache in subjects with a filter mask as opposed to surgical mask in the four aspects evaluated by the Likert scale. Likert scale rating: it indicates the degree of limitation due to headache in different areas of life. 0: none; 10: maximum. Regarding the evaluation of self-perceived work stress by means of the 12 items of the PPQ, individuals with ‘de novo’ headache versus those without headache have significantly worse scores in all aspects evaluated, except for the decrease in appetite where no significant differences are observed. Figure 2 shows graphically the evaluation of occupational stress according to the presence of headache or not. The use of a filter mask compared with surgical mask only implies a significantly worse score in two aspects: gastrointestinal discomfort (p=0.047) and greater sensation of extreme tiredness (p=0.004).
Figure 2  Evaluation of self-perceived work stress by means of the 12 items of the Psychosomatic Problems Questionnaire.