Table 5.
Association between night shift work and selected endpoints stratified by smoking status, 1988-2010.a
| Night shift work duration |
|||||||
|---|---|---|---|---|---|---|---|
| Mortality | Never | 1–5 years | 6–14 years | ≥15 years | p for trend | p-interaction | |
| All causes | |||||||
| Never smokers | No. of deaths HR (95% CI) |
1,863 1.00 (ref) |
1,833 1.04 (0.98, 1.11) |
638 1.20 (1.10, 1.31) |
457 1.04 (0.94, 1.16) |
0.05 | |
| Former smokers | No. of deaths HR (95% CI) |
2724 1.00 (ref) |
2728 0.98 (0.93, 1.03) |
916 1.06 (0.98, 1.14) |
657 1.09 (1.00, 1.19) |
0.01 | 0.15 |
| Current smokers | No. of deaths HR (95% CI) |
670 1.00 (ref) |
734 1.07 (0.96, 1.19) |
293 1.08 (0.94, 1.24) |
243 1.21 (1.04, 1.40) |
0.02 | |
| All cardiovascular diseases | |||||||
| Never smokers | No. of deaths HR (95% CI) |
411 1.00 (ref) |
430 1.11 (0.97, 1.27) |
154 1.25 (1.04, 1.51) |
139 1.25 (1.03, 1.52) |
0.01 | |
| Former smokers | No. of deaths HR (95% CI) |
516 1.00 (ref) |
521 1.00 (0.89, 1.13) |
199 1.17 (0.99, 1.38) |
146 1.16 (0.97, 1.40) |
0.03 | 0.40 |
| Current smokers | No. of deaths HR (95% CI) |
169 1.00 (ref) |
145 0.86 (0.69, 1.08) |
76 1.10 (0.83, 1.44) |
57 1.11 (0.82, 1.50) |
0.24 | |
| Ischemic heart disease | |||||||
| Never smokers | No. of deaths HR (95% CI) |
138 1.00 (ref) |
143 1.11 (0.88, 1.40) |
53 1.24 (0.90, 1.71) |
55 1.31 (0.96, 1.81) |
0.08 | |
| Former smokers | No. of deaths HR (95% CI) |
192 1.00 (ref) |
175 0.91 (0.74, 1.12) |
71 1.08 (0.82, 1.42) |
62 1.24 (0.93, 1.16) |
0.08 | 0.26 |
| Current smokers | No. of deaths HR (95% CI) |
63 1.00 (ref) |
57 0.91 (0.63, 1.31) |
41 1.63 (1.09, 2.43) |
28 1.41 (0.90, 2.22) |
0.02 | |
| All cancer | |||||||
| Never smokers | No. of deaths HR (95% CI) |
668 1.00 (ref) |
672 1.05 (0.95, 1.17) |
205 1.10 (0.94, 1.28) |
1357 0.94 (0.78, 1.13) |
0.77 | |
| Former smokers | No. of deaths HR (95% CI) |
1085 1.00 (ref) |
1102 0.99 (0.91, 1.08) |
339 1.01 (0.90, 1.15) |
235 1.04 (0.90, 1.20) |
0.58 | 0.18 |
| Current smokers | No. of deaths HR (95% CI) |
300 1.00 (ref) |
342 1.11 (0.94, 1.29) |
117 1.00 (0.80, 1.24) |
118 1.35 (1.09, 1.68) |
0.03 | |
| Lung cancer | |||||||
| Never smokers | No. of deaths HR (95% CI) |
36 1.00 (ref) |
47 1.31 (0.84, 2.03) |
12 1.27 (0.65, 2.48) |
9 1.09 (0.51, 2.33) |
0.80 | |
| Former smokers | No. of deaths HR (95% CI) |
314 1.00 (ref) |
309 0.99 (0.84, 1.16) |
90 0.91 (0.71, 1.15) |
66 0.96 (0.73, 1.26) |
0.57 | 0.17 |
| Current smokers | No. of deaths HR (95% CI) |
140 1.00 (ref) |
149 1.11 (0.86, 1.42) |
60 1.16 (0.84, 1.61) |
67 1.88 (1.36, 2.62) |
<0.001 | |
| Colorectal cancer | |||||||
| Never smokers | No. of deaths HR (95% CI) |
64 1.00 (ref) |
63 1.08 (0.76, 1.53) |
23 1.30 (0.80, 2.12) |
20 1.43 (0.85, 2.39) |
0.13 | |
| Former smokers | No. of deaths HR (95% CI) |
93 1.00 (ref) |
92 0.98 (0.73, 1.32) |
25 0.88 (0.56, 1.38) |
24 1.19 (0.75, 1.89) |
0.60 | 0.95 |
| Current smokers | No. of deaths HR (95% CI) |
20 1.00 (ref) |
14 0.74 (0.33, 1.67) |
7 1.07 (0.40, 2.87) |
6 0.94 (0.32, 2.80) |
0.89 | |
Boldface indicates statistical significance (p<0.05).
HR, hazard ratio; NHS: Nurses’ Health Study.
Cox proportional hazard model adjusted for age (continuous), alcohol consumption (none, 0.1-4.9, 5.0-14.9, ≥15.0 g/d), physical exercise (metabolic equivalent values; quintiles), multivitamin use (yes, no), menopausal status (premenopausal, postmenopausal) and post menopausal hormone use (never, past and current), physical exam in the past 2 years (no, yes for symptoms and yes for screenings), healthy eating score (quintiles), smoking status (never, former, current), pack-years (<10, 10-19, 20-39, ≥40 for former smokers; <25, 25-44, 45-64, ≥65 for current smokers), BMI (kg/m2; <21, 21-22.9, 23-24.9, 25-27.4, 27.5-29.9, 30-34.9, ≥35) ) and husband’s education (less than high school, some high school, high school graduate, college, graduate school, missingness).
p-values for interaction were obtained by adding interaction terms into the models and performing likelihood ratio tests.