Table 4 Pooled risk estimates for breast cancer and heterogeneity analysis from adjusted risk estimates
From: Night-shift work duration and breast cancer risk: an updated systematic review and meta-analysis
Factors stratified | Short-term (< 10 years) versus never night-shift work | Long-term (≥ 10 years) versus never night-shift work | ||||||
|---|---|---|---|---|---|---|---|---|
No. of studies | RR (95% CI) | \({I}^{2}\), % | P value | No. of studies | RR (95% CI) | \({I}^{2}\), % | P value | |
All studies | 26 (16, 20–22, 28, 55–75) | 1.13 (1.03–1.24) | 73.4 | 0.001 | 17 (20–22, 28, 55, 58, 62, 64–66, 69–75) | 1.08 (0.99–1.17) | 42.2 | 0.028 |
Study type | Â | Â | Â | Â | Â | Â | Â | Â |
Nested case–control | 6 (20, 21, 55–58) | 1.40 (0.9–2.19) | 66.2 | 0.011 | 4 (20, 21, 55, 58) | 1.5 (0.86–2.66) | 84.7 | 0.001 |
Case–control | 13 (16, 22, 59–69) | 1.25 (1.8–1.44) | 59.8 | 0.003 | 6 (22, 62, 64–66, 69) | 1.22 (1.02–1.46) | 0 | 0.819 |
Cohort | 7 (28, 70–75) | 1.02 (0.97–1.06) | 0 | 0.636 | 7 (28, 70–75) | 1.01 (0.95–1.07) | 0 | 0.706 |
Occupation | Â | Â | Â | Â | Â | Â | Â | Â |
Flight attendants | 2 (56, 57) | 3.94 (1.42–10.91) | 0 | 0.806 | 0 | - | - | - |
Nurses | 4 (58, 67, 68, 73) | 1.14 (0.99–1.3) | 71.6 | 0.007 | 2 (58, 73) | 1.25 (0.92–1.70) | 81.6 | 0.004 |
Other | 19 (16, 20–22, 50, 55, 59–66, 69–72, 74, 75) | 1.09 (0.97–1.22) | 68.8 | 0.001 | 14 (20–22, 28, 55, 62, 64–66, 69–72, 74, 75) | 1.03 (0.95–1.11) | 17.9 | 0.248 |
Geographic area | Â | Â | Â | Â | Â | Â | Â | Â |
Europe | 17 (16, 20, 28, 55–59, 61, 64–68, 70–72) | 1.19 (1–1.41) | 72.9 | 0.001 | 10 (20, 28, 55, 58, 64–66, 70–72) | 1.21 (1.02–1.44) | 54.4 | 0.016 |
North America | 5 (60, 62, 63, 73, 75) | 1.04 (0.96–1.13) | 39.1 | 0.145 | 3 (62, 73, 75) | 1.05 (0.94–1.16) | 0 | 0.417 |
Asia | 3 (21, 69, 74) | 1.04 (0.93–1.17) | 0 | 0.7 | 3 (21, 69, 74) | 0.94 (0.84–1.07) | 16.2 | 0.303 |
Oceania | 1 (22) | 1.25 (1.01–1.55) | - | - | 1 (22) | 1.05 (0.78–1.41) | - | - |
Adjusted for reproductive variables | Â | Â | Â | Â | Â | Â | Â | Â |
Yes | 24 (16, 20–22, 28, 55–71, 73, 74) | 1.15 (1.05–1.27) | 72.6 | 0.001 | 15 (20–22, 28, 55, 58, 62, 64–66, 69–71, 73, 74) | 1.1 (1–1.21) | 47.9 | 0.015 |
No | 2 (72, 75) | 0.94 (0.75–1.17) | 19 | 0.266 | 2 (72, 75) | 0.95 (0.76–1.19) | 0 | 0.899 |
Adjusted for family Hx | Â | Â | Â | Â | Â | Â | Â | Â |
Yes | 18 (16, 22, 28, 58–60, 62–69, 71, 73–75) | 1.11 (1.03–1.2) | 48.7 | 0.009 | 12 (22, 28, 58, 62, 64–66, 69, 71, 73–75) | 1.1 (1–1.2) | 40.2 | 0.059 |
No | 8 (20, 21, 55–57, 61, 70, 72) | 1.16 (0.83–1.62) | 83.5 | 0.001 | 5 (20, 21, 55, 70, 72) | 1.06 (0.84–1.34) | 44.1 | 0.128 |
Adjusted for confounders | Â | Â | Â | Â | Â | Â | Â | Â |
Yes | 25 (16, 20–22, 28, 55, 57–75) | 1.13 (1.03–1.23) | 71.9 | 0.001 | 17 (20–22, 28, 55, 58, 62, 64–66, 69–75) | 1.08 (0.99–1.17) | 42.2 | 0.028 |
No | 1 (57) | 3.27 (0.54–19.85) | - | - | 0 | - | - | - |
Quality category | Â | Â | Â | Â | Â | Â | Â | Â |
High | 21 (16, 20, 22, 28, 58–70, 72–75) | 1.15 (1.04–1.26) | 73.8 | 0.001 | 14 (20, 22, 28, 58, 62, 64–66, 69, 70, 72–75) | 1.1 (1–1.21) | 41.4 | 0.042 |
Moderate | 5 (21, 55–57, 71) | 1.05 (0.78–1.40) | 50.2 | 0.09 | 3 (21, 55, 71) | 1.01 (0.82–1.24) | 45.3 | 0.161 |
Source of funding | Â | Â | Â | Â | Â | Â | Â | Â |
Low risk | 22 (16, 20–22, 28, 56–60, 62, 64–73, 75) | 1.08 (1.01–1.17) | 50.2 | 0.003 | 15 (20–22, 28, 58, 62, 64–66, 69–73, 75) | 1.09 (1–1.2) | 46 | 0.02 |
Unclear | 4 (55, 61, 63, 74) | 1.36 (0.97–1.91) | 79.9 | 0.002 | 2 (55, 74) | 1.02 (0.66–1.58) | 16.7 | 0.273 |