Past Shift Work and Incident Coronary Heart Disease in Retired Workers: A Prospective Cohort Study.

Present shift work has been associated with coronary heart disease (CHD) among employed workers, but it remains unclear whether shift work in the past is still associated with CHD in retired workers. We recruited 21,802 retired workers in Shiyan, China in 2008-2010 and 2013, and followed them up for CHD events to December 31, 2018. Retired workers with longer duration of past shift work had higher CHD risks (hazard ratios for those with ≤5.0, 5.25 to 10.0, 10.5 to 20.0, and >20.0 years of past shift work were 1.05 (95% confidence interval: 0.94, 1.16), 1.08 (0.94, 1.25), 1.23 (1.07, 1.42), and 1.28 (1.08, 1.51)). The association was substantially higher among services or sales workers than among manufacturing or manual labor workers (hazard ratio for every 5-year increase in past shift work, 1.11 (95% confidence interval: 1.05, 1.16) versus 1.02 (0.98, 1.06)). Moreover, the risk was lower among those who were physically active than their inactive counterparts (P for interaction, 0.019). Longer duration of past shift work was associated with higher risk of incident CHD among retired workers, especially those from services or sales sectors. Physical exercise might be beneficial in reducing the excess risk.