Table 2 Associations of reproductive, lifestyle, and occupational factors with menstrual cycle length in 9043 participants of the Korean Nurses' Health study
From: Factors associated with regularity and length of menstrual cycle: Korea Nurses’ Health Study
Multivariable-adjusted ORs (95% CIs)a | No. of short/short or moderate | Short cycle length (< 26 days) | No. of long/moderate or long | Long cycle length (32–50 days) |
|---|---|---|---|---|
Age, years | ||||
22–25 | 180/1116 | Reference | 479/1415 | Reference |
26–30 | 288/2413 | 0.72(0.59–0.88) | 1065/3190 | 0.97(0.85–1.11) |
31–35 | 184/1473 | 0.82(0.64–1.04) | 495/1784 | 0.73(0.62–0.86) |
36–40 | 123/1025 | 0.85(0.63–1.13) | 263/1165 | 0.53(0.43–0.65) |
41–45 | 111/653 | 1.34(0.97–1.84) | 61/603 | 0.20(0.14–0.27) |
P for trend | 0.113 | < 0.001 | ||
Age at menarche, years | ||||
≤ 12 | 205/1531 | Reference | 532/1858 | Reference |
13 | 249/1848 | 1.00(0.82–1.22) | 631/2230 | 1.04(0.91–1.19) |
14 | 181/1538 | 0.85(0.68–1.05) | 556/1913 | 1.12(0.97–1.30) |
≥ 15 | 251/1763 | 1.04(0.85–1.28) | 644/2156 | 1.21(1.05–1.39) |
P for trend | > 0.999 | 0.004 | ||
Parity | ||||
Nulliparous | 617/4559 | Reference | 1816/5758 | Reference |
1 | 100/775 | 0.91(0.71–1.17) | 222/897 | 0.97(0.82–1.16) |
2+ | 168/1342 | 0.85(0.67–1.08) | 323/1497 | 1.02(0.85–1.21) |
P for trend | 0.167 | 0.901 | ||
Body mass index, kg/m2 | ||||
< 18.5 | 150/1039 | 1.12(0.92–1.36) | 428/1317 | 1.10(0.97–1.26) |
18.5– < 23 | 586/4464 | Reference | 1513/5391 | Reference |
23– < 25 | 97/684 | 1.08(0.86–1.37) | 232/819 | 1.14(0.96–1.34) |
≥ 25 | 46/458 | 0.73(0.53–1.01) | 181/593 | 1.31(1.08–1.58) |
P for trend | 0.088 | 0.059 | ||
Vigorous physical activity, METs-hours/week | ||||
None | 378/2727 | Reference | 966/3315 | Reference |
Tertile1 (< 1.95) | 170/1352 | 0.89(0.73–1.08) | 454/1636 | 0.87(0.76–1.00) |
Tertile2 (1.95–8.90) | 161/1267 | 0.90(0.74–1.10) | 507/1613 | 1.03(0.90–1.17) |
Tertile3 (> 8.90) | 177/1334 | 0.94(0.77–1.14) | 436/1593 | 0.83(0.73–0.96) |
P for trend | 0.718 | 0.034 | ||
Cigarette smoking | ||||
Never | 857/6499 | Reference | 2292/7934 | Reference |
Ever | 29/180 | 1.23(0.82–1.85) | 70/221 | 1.10(0.83–1.48) |
Alcohol drinking, g/day | ||||
None | 271/2201 | Reference | 798/2728 | Reference |
< 5 | 339/2511 | 1.12(0.94–1.33) | 849/3021 | 0.89(0.80–1.00) |
5– < 15 | 124/903 | 1.15(0.91–1.45) | 345/1124 | 0.93(0.80–1.09) |
≥ 15 | 117/763 | 1.31(1.03–1.66) | 266/912 | 0.84(0.71–0.99) |
P for trend | 0.053 | 0.116 | ||
Coffee consumption, cups/day | ||||
None | 90/651 | Reference | 287/848 | Reference |
≤ 0.5 | 383/2804 | 0.95(0.74–1.21) | 1018/3439 | 0.87(0.73–1.02) |
0.5 < –1 | 183/1504 | 0.81(0.62–1.07) | 552/1873 | 0.91(0.76–1.09) |
> 1 | 195/1418 | 0.92(0.70–1.22) | 401/1624 | 0.77(0.64–0.93) |
P for trend | 0.528 | 0.030 | ||
Rotating night shifts, nights/month | ||||
None | 288/2076 | Reference | 597/2385 | Reference |
< 7 | 309/2396 | 0.90(0.75–1.07) | 910/2997 | 1.10(0.97–1.25) |
≥ 7 | 287/2199 | 0.91(0.75–1.10) | 854/2766 | 1.01(0.88–1.15) |
P for trend | 0.257 | 0.637 | ||
On feet at work, hours/day | ||||
≤ 4 | 281/2186 | Reference | 719/2624 | Reference |
5–8 | 381/3052 | 0.98(0.83–1.16) | 1080/3751 | 0.94(0.84–1.05) |
≥ 9 | 224/1442 | 1.27(1.04–1.56) | 564/1782 | 0.95(0.82–1.09) |
P for trend | 0.081 | 0.328 | ||
Heavy lifting at work, times/day | ||||
0 | 153/1187 | Reference | 356/1390 | Reference |
1–5 | 509/3899 | 1.01(0.83–1.23) | 1426/4816 | 1.09(0.95–1.26) |
≥ 6 | 224/1594 | 1.10(0.88–1.38) | 581/1951 | 1.06(0.90–1.24) |
P for trend | 0.279 | 0.954 |