Table 2.
Relative risks of wrist and hip fractures over four, eight, and twelve years of follow-up among postmenopausal nurses by total number of years spent working in rotating night shifts as of 1988.
| Years of Rotating Night Shift Work | |||||
|---|---|---|---|---|---|
| never | 1–2 years | 3–9 years | 10–19 years | ≥ 20 years | |
| 1988–1992 Follow-up | |||||
| Wrist/Hip Fractures | 127/16 | 72/11 | 57/3 | 26/4 | 29/2 |
| Person-years | 36754 | 19325 | 20341 | 7496 | 5127 |
| Age-adjusted RRa (95% CIb) | 1.00 | 1.16 (0.88–1.53) | 0.75 (0.55–1.01) | 1.04 (0.70–1.54) | 1.43 (0.96–2.11) |
| Multivariate RRc (95% CIb) | 1.00 | 1.18 (0.89–1.55) | 0.74 (0.55–1.01) | 1.03 (0.69–1.53) | 1.43 (0.96–2.13) |
| 1988–1996 Follow-up | |||||
| Wrist/Hip Fractures | 280/36 | 167/25 | 130/17 | 63/9 | 54/10 |
| Person-years | 84005 | 44814 | 46076 | 16837 | 10909 |
| Age-adjusted RRa (95% CIb) | 1.00 | 1.17 (0.98–1.40) | 0.83 (0.68–1.01) | 1.13 (0.87–1.46) | 1.35 (1.03–1.77) |
| Multivariate RRc (95% CIb) | 1.00 | 1.19 (0.99–1.42) | 0.83 (0.68–1.01) | 1.12 (0.87–1.46) | 1.37 (1.04–1.80) |
| 1988–2000 Follow-up | |||||
| Wrist/Hip Fractures | 434/74 | 246/40 | 205/34 | 96/15 | 66/13 |
| Person-years | 137596 | 74136 | 74552 | 26881 | 16613 |
| Age-adjusted RRa (95% CIb) | 1.00 | 1.07 (0.93–1.24) | 0.85 (0.73–0.99) | 1.11 (0.90–1.36) | 1.10 (0.86–1.40) |
| Multivariate RRc (95% CIb) | 1.00 | 1.08 (0.93–1.25) | 0.86 (0.73–1.00) | 1.11 (0.90–1.36) | 1.11 (0.87–1.42) |
a
Relative risk adjusted for age and questionnaire cycle.
b
95% confidence interval.
c
Relative risk adjusted for age, body mass index, physical activity, smoking status, hormone replacement therapy use, thiazide diuretic use, diagnosis of osteoporosis, and daily intakes of calcium, vitamin D, and alcohol.