The combined effect of long working hours and individual risk factors on cardiovascular disease: An interaction analysis

OBJECTIVES: We examined whether the effect of long working hours on the risk of developing cardiovascular disease (CVD) differs depending on individual risk factors. METHODS: Seven‐year follow‐up data were extracted from the 2009 to 2016 waves of the Korea Health Panel Survey. Physician's diagnosis or medication for hypertension, diabetes, dyslipidemia, and obesity were included as chronic disease status. Smoking, drinking alcohol, and exercise levels were considered as lifestyle behavior. Hazard ratios were calculated using the Cox regression models to evaluate the risk of CVD related to chronic diseases and unhealthy behavior, based on working hour groups, after adjusting for other covariates. The interactive effects of long working hours with or without chronic diseases and unhealthy behavior on CVD were assessed using the relative excess risk due to interaction and attributable proportion measures. RESULTS: There was a statistically significant interaction between long working hours and chronic diseases within the population, especially among male participants (P‐value for interaction <.01 and .03, respectively). There were no significant interactions between unhealthy behavior and long working hours. CONCLUSIONS: Long working hours and chronic disease have a synergistic negative effect on the risk of CVD.