Using additional information on working hours to predict coronary heart disease: a cohort study

Area of Science:

• Cardiology
• Occupational Health
• Epidemiology

Background:

• Long working hours are a known risk factor for coronary heart disease (CHD).
• Traditional risk factors may not fully capture CHD risk in employed populations.
• Integrating occupational data could enhance cardiovascular risk prediction models.

Purpose of the Study:

• To evaluate if incorporating long working hours improves the Framingham risk model's accuracy for predicting CHD.
• To assess the impact of working hours on CHD risk prediction in a low-risk, employed cohort.

Main Methods:

• A cohort study (Whitehall II) of 7095 full-time employees aged 39-62 without baseline CHD.
• Baseline assessment included working hours and Framingham risk score; CHD events (coronary death, nonfatal myocardial infarction) were tracked until 2004.
• Prospective follow-up over a median of 12.3 years.

Main Results:

• Participants working ≥11 hours/day had a 1.67-fold increased CHD risk compared to those working 7-8 hours/day, after adjusting for the Framingham risk score.
• Adding working hours to the Framingham risk score resulted in a 4.7% net reclassification improvement (P=0.034).
• This improvement was driven by enhanced identification of individuals who subsequently developed CHD.

Conclusions:

• Information on working hours can enhance the predictive capability of the Framingham risk score for coronary heart disease.
• These findings are specific to low-risk, working populations and may not generalize to high-risk groups.
• Further validation in independent cohorts is recommended.