Working hours and cardiovascular disease in Korean workers: a case-control study.

OBJECTIVES Long working hours can negatively impact a worker's health. The objective of this study was to examine the association between working hours and cardiovascular diseases (CVDs) and compare the degree of risk based on CVD subtypes in Korean workers. METHODS This study was a case-control study of the patients registered in the Occupational Cardiovascular Diseases Surveillance 2010. The cases included 348 patients diagnosed with a CVD (123 cerebral infarction, 69 intracerebral hemorrhage, 57 subarachnoid hemorrhage, 99 acute myocardial infarction). Controls were 769 participants with no history of CVDs matched for gender, age, type of occupation, and region. Participants' working hours in the previous week and the average working hours over the past three months were assessed to examine short-term and long-term effects. RESULTS After adjusting for confounding factors, the odds ratios (ORs) for CVDs in the short-term were 2.66 (95% Confidence interval (CI) :1.78-3.99) for working ≤40 hours, 1.85 (95% CI: 1.22-2.81) for working 50.1-60 hours and 4.23 (95% CI: 2.81-6.39) for working >60 hours compared with the 40.1-50-hour working group. The ORs in the long-term were 2.90 (95% CI: 1.86-4.52) for working ≤40 hours, 1.73 (95% CI: 1.03-2.90) for working 48.1-52 hours and 3.46 (95% CI: 2.38-5.03) for working >52 hours compared with the 40.1-48-hour working group. CONCLUSIONS Long working hours are related to an increased risk of CVDs, and the degree of risk differs based on CVD subtype. Short working hours are also related to an increased risk for CVDs. More prospective studies targeting specific disease risks are required.