Table 1. Age and age-adjusted characteristics of participating women at baseline by rotating night shift work history.
Frequencies are given reported in absolute percent numbers and percentages (%); values are means (standard deviation), unless specified otherwise. a IQR = Interquartile range; MI= myocardial infarction.
| Sample Size | Rotating Night Shift Work Exposure (≥ 3 night shifts per month) | |||||||
|---|---|---|---|---|---|---|---|---|
| NHS (1988) | NHS2 (1989) | |||||||
| None 30,012 | <5 yrs 30,122 | 5-9 yrs 4,955 | ≥10 yrs 8,534 | None 43,657 | <5 yrs 56,179 | 5-9 yrs 9,866 | ≥10 yrs 5,833 | |
| Age | 54.0 (7.1) | 54.3 (7.1) | 54.9 (7.1) | 56.2 (6.9) | 34.8 (4.7) | 34.5 (4.7) | 35.1 (4.2) | 37.1 (3.6) |
| Race, No. (%, white) | 29,390 (98) | 29,424 (98) | 4,832 (98) | 8,250 (97) | 42,075 (96) | 53,501 (95) | 9,337 (95) | 5,479 (95) |
| Parity, No. (%) | ||||||||
| Nulliparous | 1,434 (5) | 1,795 (6) | 351 (7) | 539 (6) | 12,111 (28) | 17,814 (31) | 3,440 (36) | 1,795 (37) |
| 1 or 2 child(ren) | 10,415 (34) | 10,650 (35) | 1,761 (36) | 2,853 (35) | 23,249 (53) | 28,704 (51) | 4,889 (50) | 2,926 (48) |
| ≥3 children | 17,750 (60) | 17,211 (57) | 2,743 (55) | 4,956 (57) | 8,290 (19) | 9,653 (18) | 1,536 (15) | 1,109 (16) |
| Parental history of MI under 60 yrs, No. (%, yes) | 4,893 (16) | 5,081 (17) | 879 (18) | 1,516 (18) | 6,105 (14) | 8,294 (15) | 1,670 (17) | 1,011 (16) |
| Body Mass Index (BMI, kg/m2) | 25.2 (4.8) | 25.4 (4.8) | 26.0 (5.3) | 26.6 (5.4) | 23.9 (4.9) | 24.0 (5.0) | 24.8 (5.5) | 25.1 (5.8) |
| BMI <25, No. (%) | 18,206 (61) | 17,910 (59) | 2,683 (54) | 50 | 31,400 (72) | 39,851 (71) | 6,365 (65) | 3,420 (62) |
| BMI 25-29.9, No. (%) | 7,926 (27) | 8,107 (27) | 1,455 (29) | 30 | 7,693 (18) | 10,300 (18) | 2,068 (21) | 1,330 (22) |
| BMI 30-34.9, No. (%) | 2,645 (9) | 2,877 (10) | 545 (11) | 13 | 2,837 (7) | 3,723 (7) | 853 (9) | 606 (9) |
| BMI ≥35, No. (%) | 1,235 (4) | 1,228 (4) | 272 (6) | 7 | 1,727 (4) | 2,305 (4) | 580 (6) | 477 (7) |
| Pack-years of smoking (median, IQR)b | 18 (7-34) | 18 (6-34) | 20 (7-35) | 24 (10-39) | 10 (5-16) | 9 (5-16) | 10 (5-17) | 11 (6-19) |
| Graduate school diploma of husband, No. (%) | 5,841 (19) | 6,346 (21) | 840 (17) | 1,028 (12) | 9,351 (21) | 13,810 (25) | 2,079 (21) | 1,090 (18) |
| Alcohol intake (g/day, median, IQR)c | 1.8 (0-7.6) | 1.9 (0-8.3) | 1.8 (0-7.3) | 1.1 (0-6.2) | 0.9 (0-3.1) | 0.9 (0-3.7) | 0.9 (0-3.6) | 0.9 (0-2.9) |
| Diet score (AHEI 2010)d | 45.7 (10.5) | 46.0 (10.4) | 46.0 (10.3) | 45.3 (10.1) | 43.6 (10.5) | 44.3 (10.5) | 44.2 (10.4) | 44.1 (10.3) |
| Physical activity (Met-h/week, median, IQR)e | 7.9 (2.9-20.2) | 9.1 (3.4-20.9) | 9.0 (3.4-21.5) | 8.4 (3.2-21.5) | 12.3 (4.7-27.4) | 14.6 (5.5-31.6) | 15.1 (5.8-33.3) | 14.2 (5.2-32.1) |
| Multi-vitamin user, No. (%, yes) | 18,518 (62) | 19,011 (63) | 3,148 (64) | 5,325 (62) | 23,704 (54) | 30,053 (54) | 5,254 (53) | 3,242 (55) |
| Aspirin user, No. (%, yes) | 18,482 (62) | 19,105 (63) | 3,122 (63) | 5,374 (63) | 4,747 (11) | 6,119 (11) | 1,195 (12) | 827 (13) |
| NSAIDs user, No. (%, yes)f,f | 9,537 (31) | 9,680 (32) | 1,575 (32) | 2,728 (33) | 7,775 (18) | 10,986 (20) | 2,206 (22) | 1,409 (22) |
| Acetaminophen user, No. (%, yes)g | 11,110 (37) | 11,315 (37) | 1,849 (38) | 3,204 (39) | 9,229 (21) | 12,370 (22) | 2,292 (23) | 1,529 (26) |
| Postmenopausal, No. (%) | 20,735 (71) | 21,254 (71) | 3,674 (72) | 6,866 (74) | 965 (2) | 1,271 (2) | 247 (2) | 238 (3) |
| Current post-menopausal hormone use, No. (%) | 6,833 (23) | 7,059 (24) | 1,122 (22) | 1,868 (21) | 997 (2) | 1,263 (2) | 246 (2) | 236 (3) |
| Self-reported hypertension, No. (%) | 7,464 (25) | 7,641 (26) | 1,448 (29) | 2,781 (30) | 2,270 (5) | 2,938 (5) | 627 (6) | 460 (7) |
| Self-reported diabetes, No. (%) | 1,048 (4) | 995 (3) | 221 (4) | 507 (6) | 396 (1) | 402 (1) | 74 (1) | 68 (1) |
| Self-reported hypercholesterolemia, No. (%) | 6,683 (23) | 6,837 (23) | 1,171 (23) | 2,781 (24) | 4,493 (10) | 5,809 (10) | 1,100 (11) | 722 (11) |
| Usual sleep durationh, No. (%) | ||||||||
| ≤6 | 6,978 (23) | 7,506 (25) | 1,427 (29) | 2,901 (34) | 8,939 (20) | 12,230 (22) | 2,542 (26) | 1,670 (28) |
| 7 | 11,299 (38) | 11,353 (38) | 1,770 (36) | 2,609 (31) | 13,835 (32) | 17,397 (31) | 2,779 (28) | 1,552 (26) |
| 8-9 | 7,661 (26) | 7,358 (24) | 1,044 (21) | 1,709 (19) | 9,593 (22) | 11,178 (20) | 1,680 (17) | 892 (16) |
| ≥10 | 157 (1) | 132 (0) | 24 (0) | 56 (1) | 245 (1) | 322 (1) | 52 (1) | 37 (1) |
| Social support, No. (%, yes)i | 22,288 (94) | 22,667 (94) | 3,617 (93) | 6,019 (94) | 31,370 (94) | 39,389 (95) | 6,822 (95) | 3,930 (94) |
a
Numbers that do not add up to 100% are attributable to missing data.
b
Cumulative, amongst smokers.
c
Assessed in 1986 for NHS and in 1991 for NHS2.
d
Assessed in 1986 for NHS and in 1991 for NHS2. Higher scores as computed by the Alternative Healthy Eating Index (AHEI 2010, Chiuve et al., 2012) reflect a healthier diet.
e
Weekly energy expenditure in metabolic equivalent hours from recreational and leisure time activities.
f
Non-steroidal anti-inflammatory drugs (e.g. ibuprofen).
g
Assessed in 1990 for NHS and in 1989 for NHS2.
h
Assessed in 1986 for NHS and in 2001 for NHS2.
i
Assessed in 1992 for NHS and in 1993 for NHS2.