General characteristics of all 961 women by dysmenorrhoea status at the baseline interview, Anhui, China
| Characteristic | Dysmenorrhoea status at baseline among women included in the analysis (n = 388) | Dysmenorrhoea status at baseline in excluded women (n = 573) | ||||
|---|---|---|---|---|---|---|
| No (n = 195) | Yes (n = 193)* | p value† | No (n = 339) | Yes (n = 234) | p value | |
| *Including one subject with missing dust exposure and noise exposure information. | ||||||
| †p values are derived by t test for continuous variables and χ2 test for categorical variables. | ||||||
| ‡Women whose longest menstrual cycle ⩾40 days. | ||||||
| §Women whose shortest menstrual cycle ⩽20 days. | ||||||
| SD, standard deviation. | ||||||
| Categorical variables, n (%) | ||||||
| Long menstrual cycle ‡ | 24 (12.3) | 40 (20.7) | 0.04 | 40 (11.8) | 44 (18.8) | 0.03 |
| Short menstrual cycle § | 24 (12.3) | 20 (10.4) | 0.66 | 37 (10.9) | 23 (9.8) | 0.76 |
| Rotating shift work | 185 (94.9) | 186 (96.4) | 0.64 | 314 (92.6) | 212 (90.6) | 0.48 |
| Tea consumption | 77 (39.5) | 98 (50.8) | 0.03 | 133 (39.2) | 122 (52.1) | 0.004 |
| Perceived stress level | ||||||
| Low | 135 (69.2) | 119 (61.7) | 0.18 | 231 (68.1) | 141 (60.3) | 0.10 |
| Medium | 54 (27.7) | 61 (31.6) | 91 (26.8) | 75 (32.1) | ||
| High | 6 (3.1) | 12 (6.2) | 16 (4.7) | 18 (7.7) | ||
| Education | ||||||
| Middle school or less | 122 (62.6) | 126 (65.3) | 0.65 | 214 (63.1) | 160 (68.4) | 0.23 |
| High school or above | 73 (37.4) | 67 (34.7) | 125 (36.9) | 74 (31.6) | ||
| Dust exposure | ||||||
| Light or no | 56 (28.7) | 74 (38.5) | 0.12 | 122 (36.0) | 87 (37.2) | 0.49 |
| Moderate | 81 (41.5) | 70 (36.5) | 143 (42.2) | 88 (37.6) | ||
| High | 58 (29.7) | 48 (25.0) | 73 (21.5) | 58 (24.8) | ||
| Noise exposure | ||||||
| Light or no | 55 (28.2) | 48 (25.0) | 0.77 | 100 (29.5) | 56 (23.9) | 0.30 |
| Moderate | 68 (34.9) | 69 (35.9) | 123 (36.3) | 86 (36.8) | ||
| High | 72 (36.9) | 75 (39.1) | 115 (33.9) | 90 (38.5) | ||
| Continuous variables, mean (SD) [min, max] | ||||||
| Age (y) | 24.9 (1.6) [21.5, 31.0] | 24.9 (1.7) [21.5, 34.2] | 0.83 | 24.8 (1.6) [20.5, 33.3] | 24.8 (1.7) [21.3, 33.2] | 0.76 |
| Height (m) | 1.6 (0.1) [1.4, 1.7] | 1.6 (0.1) [1.5, 1.7] | 0.07 | 1.57 (0.05) [1.5, 1.8] | 1.58 (0.05) [1.4, 1.7] | 0.52 |
| Weight (kg) | 49.5 (6.0) [37.5, 78] | 48.9 (5.5) [35, 68] | 0.30 | 48.8 (5.7) [38, 71.5] | 48.9 (5.1) [37, 64.5] | 0.06 |
| Body mass index (kg/m2) | 19.7 (2.0) [15.6, 27.3] | 19.7 (2.1) [16, 31.4] | 0.98 | 20.1 (2.1) [15.8, 29.3] | 19.7 (1.9) [15.8, 26.2] | 0.02 |
| Age at menarche (y) | 14.7 (1.4) [12, 19] | 14.8 (1.5) [10, 18] | 0.71 | 14.7 (1.5) [11, 20] | 14.7 (1.6) [11, 19] | 0.67 |
| Average menstrual cycle length (d) | 29.1 (2.9) [20, 40] | 29.5 (3.0) [20, 40] | 0.12 | 29.2 (3.3) [20, 60] | 29.5 (4.1) [22, 50] | 0.33 |
| Average length of bleeding (d) | 5.2 (1.2) [3, 8] | 5.4 (1.3) [3, 8] | 0.05 | 5.1 (1.4) [2, 10] | 5.4 (1.3) [3, 10] | 0.01 |