TABLE 1.
Characteristics and menstrual‐related variables based on the rotating shift patterns
| No night shifts (n = 375) | Two rotating shifts (n = 679) | Three rotating shifts (n = 195) | P‐value | |
|---|---|---|---|---|
| Age (years old) | ||||
| <30 | 69 (18.4) | 274 (40.4) | 85 (43.6) | <.001 |
| ≥30 and <40 | 150 (40.0) | 226 (33.3) | 60 (30.8) | |
| ≥40 and <45 | 156 (41.6) | 179 (26.4) | 50 (25.6) | |
| BMI (kg/m2) | ||||
| ≥18.5 and <25 | 293 (78.1) | 484 (71.3) | 150 (76.9) | .090 |
| <18.5 | 47 (12.5) | 97 (14.3) | 26 (13.3) | |
| ≥25 and <30 | 23 (6.1) | 73 (10.8) | 11 (5.6) | |
| >30 | 12 (3.2) | 25 (3.7) | 8 (4.1) | |
| Hospital size | ||||
| >300 beds | 107 (28.5) | 381 (56.1) | 119 (61.0) | <.001 |
| 100‐299 beds | 94 (25.1) | 226 (33.3) | 64 (32.8) | |
| <100 beds | 25 (6.7) | 40 (5.9) | 11 (5.6) | |
| Clinic, nursing home | 149 (39.7) | 32 (4.7) | 1 (0.5) | |
| Department in which the women worked in | ||||
| Out‐patient clinic | 240 (64.0) | 63 (9.3) | 8 (4.1) | <.001 |
| Wards | 118 (31.5) | 530 (78.1) | 157 (80.5) | |
| ICU, OR, ER | 17 (4.5) | 86 (12.7) | 30 (15.4) | |
| Irregular menstrual cycles a | 93 (24.8) | 254 (37.4) | 70 (35.9) | .001 |
| Cycle length ≤21 d or ≥39 d at least a few times | 78 (20.8) | 212 (31.2) | 59 (30.3) | |
| Amenorrhea ≥3 mo | 15 (4.0) | 42 (6.2) | 11 (5.6) | |
| Abnormal menstrual period b | 30 (8.0) | 45 (6.6) | 18 (9.2) | 0.629 |
| 1‐2 d | 9 (2.4) | 15 (2.2) | 4 (2.1) | |
| ≥8 d | 21 (5.6) | 30 (4.4) | 14 (7.2) | |
| Dysmenorrhea or premenstrual symptoms affected their work c | 236 (62.9) | 463 (68.2) | 132 (67.7) | .429 |
| Sometimes | 199 (53.1) | 379 (55.8) | 108 (55.4) | |
| Often | 37 (9.9) | 84 (12.4) | 24 (12.3) | |
Data are shown in n (%). Statistical significance was calculated using chi‐square test.
Abbreviations: BMI, body mass index; ER, emergency room; ICU, intensive care unit; OR, operating room.
a
Normal menstrual cycle length is >22 and <39 d.
b
Normal menstrual period is 3‐7 d.
c
Dysmenorrhea and premenstrual symptoms do not affect their work in a normal person.