Segmented Linear Regression Models for Assessing Change in Retrospective Studies in Healthcare

Figure 5

120-day mortality versus time t in days from the start of the study. The vertical dashed line marks the onset of the HFU. The black line shows single line as the best-fitting linear model for the entire period: equation y = −0.00003t + 0.1529. The dashed blue lines are the best fitting linear models for the pre-HFU and post-HFU periods. The best model for the pre-HFU period is the single line with equation y = −0.00003t + 0.1519, and the best model for the post-HFU period is the single line with equation y = −0.00025 (t−1550) + 0.1497. Data points 0 or 1 for dead or alive in red.