Figure 3.

Meta-analysis of prospective studies on the risk of breast cancer associated with long-duration night shift work. A) Worked night shifts for 20 or more years vs never worked night shifts. B) Worked night shifts for 30 or more years vs never worked night shifts. *Results for 20 to 29 years not reported separately. †Approximate numbers, estimated from confidence limits. ‡Worked night shifts for more than 27.5 years. Study-specific relative risks (RRs) are represented by squares (with their 95% confidence intervals [CIs] as lines), each with area inversely proportional to the variance of the log RR. RRs were combined using inverse-variance-weighted averages of the log RRs in the separate studies, yielding a result and its 95% CI, which is plotted as a diamond.